Chain Rearrangement Research Articles

Understanding the structural changes, interfacial mechanisms, and mechanical properties of polymer/MWCNT nanocomposites after microwave treatment

AbstractThe use of microwave radiation for the post‐processing treatment of engineering polymers is a recent trend not seen by many. In the case of polymers, their crystalline nature is a significant factor in optimizing the treatment time for maximum improvement in mechanical properties. With the advent of nanomaterials, the aim of the present work is to explore the possibility of post‐processing microwave treatment on the structure and property relationships in MWCNT‐reinforced polymer matrices. The microwave‐activated nucleating tendency of MWCNTs was found to be promoting molecular chain rearrangement in poly‐amide (PA) and poly‐butylene‐terephthalate (PBT) nanocomposites. This considerably improved the mechanical characteristics of the composites by facilitating the rearrangement of the crystalline segments of the polymer matrix. The wear performance of PA nanocomposite increased by 30%, while the elongation of PBT nanocomposite increased by 93%, after a treatment of only 15–20 s. However, comparing with previous studies, it was found that, similar to virgin polymers, the treatment time needed for maximum improvement in polymer/MWCNT nanocomposites is hugely dependent on polymer matrix crystallinity as well. A detailed analysis of the microwave‐treated nanocomposites' structure and mechanical properties illustrates the post‐processing microwave treatment as a time‐efficient, cost‐effective, and environmentally friendly technique.Highlights Direct use of microwave radiation to heat the finished polymeric component. Microwave treatment brings about structural changes resulting in enhanced properties. Instantaneous heating is a key reason for the systematic arrangement of polymeric chains. Microwave‐activated nucleating tendency of MWCNTs also promotes chain arrangement. Properties increase as high as 30% wear rate and 93% elongation.

Eco‐friendly production and performance evaluation of water‐resistant cellulose nanofiber bioaerogels

AbstractA sustainable and environmentally conscious approach was employed to create a cellulose nanofiber (CNF) bioaerogel. This modified technique was used for its affordability and eco‐friendly nature, involved the use of reduced concentrations of NaOH solution (ranging from 0 to 0.5 M) to disperse the CNFs. The process included mixing, freezing, neutralizing, and freeze‐drying, ultimately resulting in well‐structured 3D bioaerogels. The concentration of NaOH had a significant impact on the properties of the bioaerogels. The density of the aerogels increases with higher concentration of NaOH. All treated aerogels exhibited impressive water resistance and maintained their structural integrity when exposed to water, indicating promising practical applications. This enhanced structural integrity is attributed to CNF chain rearrangement, facilitated by CNF swelling, dissolution in NaOH, and homogenization. FTIR and XRD analyses provided insight into the transition from cellulose I to cellulose‐II in the bioaerogel structure. These findings contribute to the development of eco‐friendly bioaerogels for environmentally conscious applications. Further research is needed to gain a deeper understanding of the process and to optimize conditions for specific bioaerogel properties.

High Gas Permeability in Aged Superglassy Membranes with Nanosized UiO‐66−NH2/cPIM‐1 Network Fillers

AbstractSuperglassy membranes synthesised by polymers of intrinsic microporosity (PIMs) suffer from physical aging and show poor gas permeance over time, especially thin membranes, due to the fast rearrangement of nonequilibrium polymer chains. Herein, we constructed a novel PIM‐1 thin film nanocomposite membrane (TFN) using nanosized UiO‐66−NH2 (≈10 nm)/carboxylated PIM‐1 (cPIM‐1) as the composite filler. Unlike conventional fillers, which interact with the polymer only via the surface, the UiO‐66−NH2/cPIM‐1 forms a stable three‐dimensional (3D) network intertwining with the polymer chains, being very effective to impede chain relaxation, and thus physical aging. Nanosizing of UiO‐66−NH2 was achieved by regulating the nucleation kinetics using carbon quantum dots (CQD) during the synthesis. This led to increased surface area, and hence more functional groups to bond with cPIM‐1 (via hydrogen bonding between −NH2 and −COOH groups), which also improved interfacial compatibility between the 3D network and polymer chains avoiding defect formation. As a result, the novel TFN showed significantly improved performance in gas separation along with reduced aging (i.e. ≈6 % loss in CO2 permeability over 63 days); the aged membranes had a CO2 permeance of 2504 GPU and ideal selectivity values of 37.2 and 23.8 for CO2/N2 and CO2/CH4, respectively.

High Gas Permeability in Aged Superglassy Membranes with Nanosized UiO-66-NH2 /cPIM-1 Network Fillers.

Superglassy membranes synthesised by polymers of intrinsic microporosity (PIMs) suffer from physical aging and show poor gas permeance over time, especially thin membranes, due to the fast rearrangement of nonequilibrium polymer chains. Herein, we constructed a novel PIM-1 thin film nanocomposite membrane (TFN) using nanosized UiO-66-NH2 (≈10 nm)/carboxylated PIM-1 (cPIM-1) as the composite filler. Unlike conventional fillers, which interact with the polymer only via the surface, the UiO-66-NH2 /cPIM-1 forms a stable three-dimensional (3D) network intertwining with the polymer chains, being very effective to impede chain relaxation, and thus physical aging. Nanosizing of UiO-66-NH2 was achieved by regulating the nucleation kinetics using carbon quantum dots (CQD) during the synthesis. This led to increased surface area, and hence more functional groups to bond with cPIM-1 (via hydrogen bonding between -NH2 and -COOH groups), which also improved interfacial compatibility between the 3D network and polymer chains avoiding defect formation. As a result, the novel TFN showed significantly improved performance in gas separation along with reduced aging (i.e. ≈6 % loss in CO2 permeability over 63 days); the aged membranes had a CO2 permeance of 2504 GPU and ideal selectivity values of 37.2 and 23.8 for CO2 /N2 and CO2 /CH4 , respectively.

Photo-cured phase change energy storage material with photo-thermal conversion, self-cleaning and electromagnetic shielding performances via the lamellar structure strengthened by segment rearrangement of dynamic disulfide bond

At present, phase change materials (PCMs) with single function hardly meet the needs of advanced intelligent materials in practical applications, and the multifunction integration is the current trend. However, photo-cured multifunctional PCMs are hampered by insufficient transparency due to adding functional fillers, such as carbon and metal materials. The novel strategy is necessary to overcome this limitation. Here, a photo-cured multifunctional PCM is prepared by using the design of a lamellar structure composing the photo-cured phase change polymer layer and the functional fillers layer. The curing of the phase change polymer is realized by the photo-induced "thiol-ene" click reaction, and reversible dynamic disulfide bonds are introduced into the PCM, which not only gives the phase change crosslinked network reprocessability, but also strengthens the interface layer by the chain rearrangement to form a stable composite structure. The carboxylated multiwalled carbon nanotubes (CCNTs) and silver nanowires (AgNWs), as functional fillers, give the PCM photo-thermal conversion, self-cleaning and electromagnetic shielding (EMI SE) performances. Its phase change latent heat and photo-thermal conversion can reach 105.2 J/g and 78.5%, and the water contact angle is 142° with self-cleaning performance. In addition, due to the dense and well-developed conductive path formed by AgNWs layer on the PCM surface, the EMI SE effect can reach 39 dB with only 6.3% (in mass) filler content and 7.2% phase change latent heat loss. As far as we know, this is the first report about photo-cured PCMs with self-cleaning, photo-thermal conversion and EMI SE performances.

T-Cell Lgll of the Γδ Subtype: Clinically Relevant Fact or Academically Interesting Finding?

Large granular lymphocyte leukemia (LGLL) is a rare group of mature T and NK cell lymphoproliferative disorders, with an annual incidence of 0.2 - 0.72 cases per 1 million individuals. Median age of onset is 65, with case prevalence roughly equivalent between sexes. T-Cell LGLL (T-LGLL) makes up 85-91% of cases. The majority of T-LGLL clones express Tαβ, with only 5% of cases expressing Tγδ. Outcomes and treatment data on this subtype is limited. Recent observational data suggest reduced overall survival (OS), increased incidence of cytopenias and associated autoimmune diseases, and favorable response to first line therapy with cyclosporine, in comparison to the Tαβ subtype. Here, we summarize disease biology and clinical presentation and provide review of recent literature describing clinical course and treatment options in the context of a patient case. A woman in her early 70's with osteoporosis, asthma and hypertension presented to hematology after she was found to have leukocytosis of 12.1* 103/µL during routine lab work. CBC w/differential showed lymphocytosis of 11.0* 103/µL with absolute neutrophil count of 496 *103/µL and thrombocytopenia (121* 103/µL). She was asymptomatic without history of malignancy or autoimmune disease, prior available labwork was normal and physical exam was unremarkable. Peripheral smear showed atypical lymphocytes, with flow cytometry demonstrating 50.45% clonality with CD2+, CD3+, CD4-, CD7+, CD8 +/- , CD16+, CD 56-, CD57+/-, Tγδ + phenotype. Bone marrow biopsy demonstrated hypercellular (70%) marrow with scattered lymphoid aggregates with clonal infiltration of 20% core cellularity by CD3 immunohistochemistry. Bone marrow flow demonstrated the T-Cell phenotype seen in peripheral blood. T-Cell clonality study demonstrated TCR gamma chain rearrangement. PET/CT showed mildly increased FDG uptake throughout bone marrow. Next-Generation Sequencing confirmed mutations of STAT3 (D661Y), ASXL1, and TET2. There is conflicting data on whether Tγδ positivity portends reduced OS compared to Tαβ. Observational studies show that Tγδ is more frequently symptomatic and conveys higher risk of cytopenias. Not all cases require treatment. Treatment is usually prompted by single-lineage cytopenias. First line single agent therapy with methotrexate (MTX), cyclosporine, and cyclophosphamide have shown similar overall response rates of 40-50%, though STAT3 mutated disease is associated with better response to MTX. STAT3 mutations are associated with more severe cytopenias, more frequent autoimmune/inflammatory disorders, and more frequently required therapy, however neither STAT mutations nor cytopenias convey decreased OS in Tγδ disease. STAT3 and STAT5b mutations occur in 40% of all LGLL cases, with STAT3 mutations associated with neutropenia and rheumatoid arthritis. Nearly two thirds of STAT3 genetic mutations are Y640F and D661Y. Our patient was initiated on prednisone, though due to poor tolerance was transitioned to MTX titrated to 12.5 mg weekly. She has remained on this dose with good tolerability for 18 months with resolution of lymphocytosis and improvement in neutropenia. T-LGLL has an OS of 9 years. Rarity of Tγδ disease has limited the ability to generate subtype specific survival data. The largest retrospective study to date included 137 Tγδ patients across 8 centers and provided a signal that Tγδ disease may predict reduced OS compared to the Tαβ subtype, however data was limited by disparate median follow-up time amongst cohorts due to high rates of censorship in the Tγδ cohort. Median OS was not reached at median follow up time of 48 months. This trend would be clinically expected given that Tγδ subtype has been consistently associated with severe cytopenias and autoimmune diseases, but should not be accepted until higher quality evidence is generated over longer median follow-up times. The same study found better responses to cyclosporine as first line therapy, an interesting observation as MTX has been generally accepted as first line therapy based on predominantly retrospective studies, though these studies did not stratify treatment responses by TCR phenotype. These findings underscore the need for prospective studies characterizing Tγδ specific disease course, survival analyses and treatment response.

The Effect of Preemptive Rituximab Treatment in Patients with EBV Viremia after Solid Organ Transplantation on the Development of Post-Transplant Lymphoproliferative Disorder

The association between Epstein-Barr Virus (EBV) reactivation after solid organ transplantation (SOT) and Post-Transplant Lymphoproliferative Disorder (PTLD) is well described. There are currently no guidelines regarding the use of rituximab preemptively in patients with EBV viremia after SOT to reduce the risk of PTLD. We sought to determine whether rituximab in SOT patients with EBV viremia has benefit in preventing PTLD. This retrospective analysis of electronic medical record data identified SOT recipients who experienced EBV viremia post-transplant between January 2010 and February 2023 at Columbia University Irving Medical Center (CUIMC). Data queries were clinically reviewed. Logistic regression analysis was performed to investigate the relationship between predictor variables including rituximab administration, log-transformed EBV peak titer, duration of EBV viremia, and time from SOT to EBV reactivation, with the binary primary outcome of PTLD diagnosis status. The analysis encompassed both univariate and multivariate logistic regression. There were 2,168 patients who met the inclusion criteria of having EBV reactivation after SOT, out of 6,395 total SOT performed at CUIMC during this timeframe. Patient characteristics are described in table 1. The median peak EBV titer was 154 (range: not quantifiable - 5,335,816), the median duration of EBV viremia was 78 days (range: 1 - 6,980), and the median time from SOT to EBV reactivation was 688 days (range: 0-11103). Of the 2,168 patients, 185/2168 (8.5%) received rituximab for indications other than PTLD including EBV viremia, treatment of rejection, antibody desensitization therapy/immunosuppression peri-transplant, and other non-transplant related indications (e.g. lupus nephritis). Of the patients who received rituximab, 182/185 (98.4%) did not develop PTLD. The 3/185 (1.6%) patients who did develop PTLD were all ≤ 20 years-old at time of diagnosis, and had EBER(+), monomorphic PTLD, diffuse large B-cell lymphoma type, with a non-germinal center phenotype, involving the gastrointestinal tract. Two were CD20 positive, all 3 had partial weak CD30 positivity, and all 3 had clonal immunoglobulin heavy chain rearrangements. Among the patients who did not receive preemptive rituximab post-SOT, 195/1983 (9.8%) developed PTLD, whereas 1788/1983 (90.2%) did not. Prior rituximab therapy for any indication in patients with EBV viremia post-SOT was associated with lower risk of subsequent PTLD by univariate analysis (0.14% vs 8.39%, OR 0.15, p = 0.0013, 95% CI 0.048-0.48). Receipt of rituximab (OR 0.12, p=0.0002), log-transformed peak EBV titer (OR 1.10, p<0.0001), and duration of EBV viremia in months (OR 1.01, p<0.0001) were all independently associated with risk for PTLD by multivariate analysis (figure 1). The relationship between time from SOT to EBV viremia was not significantly associated with development of PTLD. This retrospective analysis suggests that administering preemptive rituximab in SOT patients with EBV viremia may lower the risk of developing PTLD. The fact that peak EBV titer and duration of EBV viremia remain associated with PTLD in multivariate analyses suggests that the benefit of rituximab may be independent of the degree or duration of EBV viremia. A prospective analysis of factors such as area under the curve of EBV exposure, HLA status, T cell clonotype diversity, organ type, and immunosuppression type, is needed to better understand individual risks for improved selection of those who would benefit from preemptive rituximab.

Novel Physically-Crosslinked Caffeine and Vitamin C-Loaded PVA/Aloe Vera Hydrogel Membranes for Topical Wound Healing: Synthesis, Characterization and In-Vivo Wound Healing Tests

Novel physically-crosslinked PVA membranes blended with Aloe vera extract were fabricated by solution-casting method. Physically-crosslinking process is depending on the rearrangement of PVA chains forming intermolecular hydrogen bonding with removal of water molecules using propanol as a stabilizing agent. The structure of crosslinked membranes was characterized by FT-IR, SEM, TGA, and XRD analyses and confirmed via gel faction and swelling ratio studies. Caffeine and vitamin C loaded-PVA/Aloe vera membranes were bio-assessed in terms of their impact on the wound healing using Wistar albino rats as an animal model. In vitro evaluation includes protein adsorption showed that the fabricated membranes improved significantly the wound healing ability via enhancing the tissue platelet aggregation. In addition, resulting adequate in vitro release behavior for the loaded ingredients in the potential application. In-vivo results displayed that rats full-thickness wounds were remarkably reduced after PVA/Aloe vera/Vitamin C membranes treatment, as shown by a reduction in the area of the wounds when compared to wounds treated with cotton gauze and PVA/Aloe vera membranes. Furthermore, the treated wounds with PVA/Aloevera/caffeine show more wound closer comparing to that incorporate vitamin C and the PVA/Aloevera incorporated both caffeine and vitamin C give the most significant healing that show reappearance of hair covered the wound area. Histological examinations of wounds covered in membranes showed a successful re-epithelialization, demonstrating caffeine's and vitamin C’s efficacy. These results demonstrated that, PVA/Aloe Vera/Caffeine and PVA/Aloe vera/vitamin C membrane have remarkable wound healing and skin regeneration properties.Graphical

Presence of leukemic clone-specific immunoglobulin heavy chain rearrangements in neonatal blood spots of children with B-cell precursor acute lymphoblastic leukemia.

Childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) can be traced back to birth using leukemic clone-specific immunoglobulin heavy chain (IGH) rearrangements, implying prenatal origin of this disease. We retrospectively analyzed neonatal blood spots (Guthrie cards) of 24 patients with childhood BCP-ALL aged 1-9.6 years (median 3.1 years) for the presence of clonotypic IGH rearrangements identified in diagnostic bone marrow samples. Based on the sequences of IGH rearrangements, 2 patient-specific primers were designed for each patient and used in semi-nested polymerase chain reaction for the detection of preleukemic clones at birth. Clonotypic IGH rearrangements were detected in neonatal blood spots of 54.2% of patients (13/24). In two cases with double IGH rearrangements detected at diagnosis, only one rearrangement was present at birth, while in the third case both leukemic rearrangements were detected in neonatal blood. Guthrie card-positive findings were significantly more frequent in children ≤5 years of age than in older children (p = 0.011). Regarding patients' characteristics at birth and at diagnosis, Guthrie card-positivity was not associated with sex, birth weight and mother's age, as well as with white blood cell count, percentage of bone marrow blasts, immunophenotype and the presence of ETV6/RUNX1 and TCF3/PBX1 fusion genes at diagnosis. Our study confirms that a large proportion of childhood BCP-ALL originates in utero, regardless of the molecular subtype defined by chromosomal aberrations. The observed trend toward younger age at diagnosis in Guthrie card-positive versus Guthrie card-negative patients implies that the age at diagnosis depends on the presence of preleukemic clone at birth, as well as on the timing of postnatal transforming genetic events.

A decade of CD4+ chimeric antigen receptor T-cell evolution in two chronic lymphocytic leukemia patients: were chronic lymphocytic leukemia cells present?

On Feb 2, 2022, Nature published the paper titled "Decade-long leukemia remissions with the persistence of CD4+ CAR T-cells" (Nature. 2022;602:503-9. doi: 10.1038/s41586-021-04390-6). According to the results presented, it could be argued that "chimeric antigen receptor (CAR) T-cells can actually cure patients with chronic lymphocytic leukemia (CLL)". CAR T-cells remained detectable more than ten years after infusion, and immunoglobulin heavy chain (IGH) rearrangement deep sequencing showed persistent deep molecular remission for both patients (no CLL clonotypes were detectable six months after CAR T-cell infusion and onwards). However, the existing actual disease status of both patients remained unclear, as it was unknown: (1) if CAR T-cells killed all leukemia cells during the initial anti-leukemic response phase, that is, soon after CAR T-cell infusion into both patients; (2) if few CLL cells survived, but persistent CAR T-cells had been able to destroy any leukemia cells before they reach detectable levels. In the first case, both patients could be considered definitely cured; in the second not and their decade-prolonged deep remission could be a consequence of the cytotoxic activity of the functionally active CD4+ CAR T-cells. The first version appears to be stronger and the supporting arguments have been included in a comprehensive commentary article. A new therapeutic intervention may emerge with the potential to fully improve the quality of life of both patients and in addition, ongoing research into CAR T-cells may turn in a new, more effective direction.

Lotus starch/bamboo shoot polysaccharide composite system treated via ultrasound: Pasting, gelling properties and multiscale structure

This study investigated the effects of ultrasound treatment on the physicochemical properties, digestion properties, and multiscale structure of a lotus root starch (LS) and bamboo shoot polysaccharide (BSP) composite system. It also preliminarily revealed the mechanism underlying the modification effect of ultrasound treatment. After 180–360 W ultrasound treatment, the viscosity, thixotropy, and gel viscoelasticity of the LS/BSP paste increased. However, treatment with the ultrasound power of 540 and 720 W decreased viscoelasticity. After 14 days of retrogradation, the hardness and cohesiveness of the LS/BSP gel increased under 180 and 360 W ultrasound treatment but decreased under 540 and 720 W ultrasound treatment. After 540 W ultrasound treatment, RDS content decreased by 17.2 % and resistant starch content increased by 32.5 %. After 180 min of in vitro digestion, the hydrolysis rate of LS/BSP decreased from 97.82 % to 93.13 % as the ultrasound power increased to 540 W. Ultrasound promoted the uniform dispersion of BSP in the starch paste and the movement, orientation, rearrangement, and aggregation of starch and BSP molecular chains. These effects further enhanced the interaction between BSP and starch, resulting in the formation of a dense paste structure with strong resistance to digestive enzymes. This work revealed the mechanism of the effects of ultrasound treatment on LS/BSP and found that 360–540 W ultrasound treatment could improve the physicochemical properties and digestion properties of LS/BSP.

Effect of sintering on processability vis‐a‐vis microcellular foaming of ultrahigh molecular weight polyethylene

AbstractProcessing of ultrahigh molecular weight polyethylene (UHMWPE) involves sintering due to its high melt strength and no flowability above melting temperature. Variations in compression molding pressure during sintering lead to chain rearrangement at the sintered interphase and the boundary, affecting foamability. UHMWPE particles are sintered using compression molding; samples are prepared at two different pressures: UHPE‐HP (80 bar) and UHPE‐LP (40 bar) at 180°C. The sintering phenomenon of UHMWPE particles is observed through an optical microscope, and their effect on foaming was observed. UHPE‐HP foams are systematically studied to obtain the foaming window. Increasing foaming pressure (80–120 bar) made UHPE‐HP foams softer (0.350–0.219 g/cm3) with varying average cell size (26.37–46.1 μm) and foam cell density (3.98 × 107–1.06 × 108 cells/cm3), and compression modulus decreased from 9 to 5.4 MPa. DMA results showed a strong dependence of stiffness on crystallinity, and foamed samples exhibit higher stiffness than their unfoamed counterpart. The storage modulus for foamed samples decreases with increase in the gas content. The UHPE‐LP foam is relatively softer, with a lower foam density (0.233 g/cm3), a higher expansion ratio, bigger average foam cells (35.13 μm), and lower foam cell density (9.33 × 107 cells/cm3). This is due to constrained crystallinity at the interphase and pre‐existing cavities, favoring the foaming.

Effect of polymer molecular weight on the long-term process stability of crosslinked polybenzimidazole organic solvent nanofiltration (OSN) membranes

The importance of polymer molecular weight on the long-term performance of polybenzimidazole (PBI) membranes in organic solvents was investigated. PBI membranes were manufactured from two different polymer molecular weights: the standard molecular weight of PBI polymer, used almost universally across literature for organic solvent stable membranes (∼27,000 g mol-1), and an untested ∼ two-fold higher molecular weight (∼60,000 g mol-1). After crosslinking, all PBI membranes were chemically and mechanically stable. However, during continuous long-term pressurised filtration in DMF, the standard molecular weight PBI membranes suffered slow permeance decline over time. This was attributed to rearrangement of the crosslinked polymer chains. Increasing the extent of crosslinking reduced the rate of membrane permeance decline but did not provide a fully process stable membrane. Using a higher molecular weight PBI, and a similar extent of crosslinking, resulted in a membrane with constant permeance and excellent process stability, even during continuous DMF filtration at 120 °C. This was attributed to the increased interchain interactions and entanglement in the high molecular weight polymer, which reduced the rate of chain rearrangement and compaction. This work demonstrates the importance of polymer molecular weight for reducing membrane compaction and providing process stability in organic solvents.

Open structure and gating of the Arabidopsis mechanosensitive ion channel MSL10

Plants are challenged by drastically different osmotic environments during growth and development. Adaptation to these environments often involves mechanosensitive ion channels that can detect and respond to mechanical force. In the model plant Arabidopsis thaliana, the mechanosensitive channel MSL10 plays a crucial role in hypo-osmotic shock adaptation and programmed cell death induction, but the molecular basis of channel function remains poorly understood. Here, we report a structural and electrophysiological analysis of MSL10. The cryo-electron microscopy structures reveal a distinct heptameric channel assembly. Structures of the wild-type channel in detergent and lipid environments, and in the absence of membrane tension, capture an open conformation. Furthermore, structural analysis of a non-conductive mutant channel demonstrates that reorientation of phenylalanine side chains alone, without main chain rearrangements, may generate the hydrophobic gate. Together, these results reveal a distinct gating mechanism and advance our understanding of mechanotransduction.

In vitro degradation of fibrous bilayer poly-L-lactic acid scaffolds

Polymer degradation and mechanical properties are of paramount importance in tissue engineering. The degradation rate of polymeric scaffolds is influenced by several important material and environmental factors. In particular, the mechanical support provided by the scaffold to the surrounding tissue during tissue regeneration is critical for that it directly impacts the cell behavior through mechanical signals sensed by mechanoreceptors on the cell surface. Consequently, the principal objective of the present study was to investigate the degradation behavior of electrospun poly-L-lactic acid (PLLA) bilayer microfibrous scaffolds in pH-neutral medium. Changes in the morphology, molecular weight, crystallinity, mass loss, and thermomechanical properties of the scaffolds over an extended period were studied by scanning electron microscopy, differential scanning calorimetry, gel permeation chromatography, and tensile testing. An interplay between chain scission and orderly chain rearrangement in the polymer scaffold commenced during degradation, leading to the decrease of the molecular weight and stiffness, a constant mass loss, and an increase in crystallinity, tensile strength, and glass transition temperature, with virtually constant yield strength and melting temperature. The unchanged structure morphology and adequate matrix stiffness after prolonged degradation illuminated the potential of the bilayer PLLA scaffolds for tissue engineering and drug delivery applications. Nonetheless, modifications to the scaffold structure or surface may be required to accordingly tune the degradation rate in these applications. The experimental methodology introduced in this study can be extended to potentially investigate material degradation in other fields, such as agriculture, packaging, and disposable products.

Facile post-treatment of PSf membranes with hexane for fractionation and concentration of alkaline textile wastewater

To treat dyeing and printing industrial wastewater with zero liquid discharge, developing a straightforward technique for fabricating membranes with sufficient alkaline and salt resistance is crucial. This study presents a facile n-hexane post-treatment method to enhance the ability of polysulfone (PSf) membranes to fractionate textile wastewater. The optimal membrane exhibits minimal salt rejections, with only 5.1 % for NaCl and 9.8 % for Na2SO4. Additionally, it demonstrates exceptional dye rejection rates, reaching 99.87 % for Direct Red 23 and 99.81 % for Congo Red while maintaining high-water permeance (∼52 L m−2h−1 bar−1) at the alkaline environment (pH = 13) and high salt (30 g/L). Furthermore, a combined diafiltration process was devised for the separation of a mixture containing Congo Red and Na2SO4. This process achieved an impressive desalination efficiency of 98 % while ensuring a remarkable dye recovery of 99.8 %. The outstanding performance can be attributed to the favorable solvency capability of n-hexane, which was determined based on the analysis of Hansen solubility parameters. Through a two-minute solvent treatment of PSf membranes, the flexibility of the polymer chains within the membranes was enhanced, leading to a denser structural arrangement. This arrangement resulted in the formation of highly selective membranes. The extent of densification is influenced by several factors, such as solvent type, immersion duration, and polymer concentrations. These variables directly affect the level of solvation and chain rearrangement that occurs during the process. This study underscores the potential significance of solvent treatment as a post-treatment step in membrane fabrication, demonstrating its utility as a tool for fine-tuning separation performance in applications that involve dye/salt mixtures, and highlighting its importance in the field of membrane technology.

Shared bias in H chain V-J pairing in naive and memory B cells.

H chain rearrangement in B cells is a two-step process where first DH binds JH, and only then VH is joined to the complex. As such, there is no direct rearrangement between VH and JH. Nevertheless, we here show that the VHJH combinations frequency in humans deviates from the one expected based on each gene usage frequency. This bias is observed mainly in functional rearrangements, and much less in out-of-frame rearrangements. The bias cannot be explained by preferred binding for DH genes or a preferred reading frame. Preferred VH JH combinations are shared between donors. These results suggest a common structural mechanism for these biases. Through development, thepreferred VH JH combinations evolve during peripheral selection to become stronger, but less shared. We propose that peripheral Heavy chain VH JH usage is initially shaped by a structural selection before the naive B cellstate, followed by pathogen-induced selection for host specific VH-JH pairs.

Analytical Pyrolysis of Pinus radiata and Eucalyptus globulus: Effects of Microwave Pretreatment on Pyrolytic Vapours Composition.

Pinus radiata (PR) and Eucalyptus globulus (EG) are the most planted species in Chile. This research aims to evaluate the pyrolysis behaviour of PR and EG from the Bío Bío region in Chile. Biomass samples were subjected to microwave pretreatment considering power (259, 462, 595, and 700 W) and time (1, 2, 3, and 5 min). The maximum temperature reached was 147.69 °C for PR and 130.71 °C for EG in the 700 W-5 min condition, which caused the rearrangement of the cellulose crystalline chains through vibration and an increase in the internal energy of the biomass and the decomposition of lignin due to reaching its glass transition temperature. Thermogravimetric analysis revealed an activation energy (Ea) reduction from 201.71 to 174.91 kJ·mol-1 in PR and from 174.80 to 158.51 kJ·mol-1 in EG, compared to the untreated condition (WOT) for the 700 W-5 min condition, which indicates that microwave pretreatment improves the activity of the components and the decomposition of structural compounds for subsequent pyrolysis. Functional groups were identified by Fourier transform infrared spectroscopy (FTIR). A decrease in oxygenated compounds such as acids (from 21.97 to 17.34% w·w-1 and from 27.72 to 24.13% w·w-1) and phenols (from 34.41 to 31.95% w·w-1 and from 21.73 to 20.24% w·w-1) in PR and EG, respectively, was observed in comparison to the WOT for the 700 W-5 min condition, after analytical pyrolysis. Such results demonstrate the positive influence of the pretreatment on the reduction in oxygenated compounds obtained from biomass pyrolysis.

Scott Blair Fractional-Type Viscoelastic Behavior of Thermoplastic Polyurethane.

In this paper, the experimental characterization of the viscoelastic properties of thermoplastic polyurethane (TPU) samples through creep experiments is presented. Experiments were conducted at different constant temperature levels (15, 25, and 35 ∘C), for three different tensile stress levels (0.3, 0.5, and 0.7 MPa), and at different physisorbed water contents, providing access to: (i) the temperature dependency of creep parameters and (ii) the assessment, if behavior is indeed viscoelastic. The physisorbed water content was achieved by exposing virgin samples to environments with relative humidity ranging from 0 to 80 percent until mass stability was reached. Creep tests were conducted immediately afterwards with this particular humidity level. The main results of this study are as follows. The temperature dependency of the obtained creep parameters is well described in Arrhenius plots. With regard to water content, two prototype material responses were observed in the experimental program and accurately modeled using the following fractional-type models: (i) Scott Blair-type (i.e., power-law-type) only behavior, pronounced for the combination of low water content/low temperature; (ii) combined Scott Blair plus Lomnitz (i.e., log-type) behavior for high water content/high temperature. This change in behavior associated with certain thresholds for the specified environmental conditions (temperature and relative humidity) may indicate the initiation of hydrogen bond breakage and rearrangement (carbamate H-bonds and physisorbed water H-bonds). Regarding the short-term or quasi-instantaneous behavior, the Scott Blair element seems highly appropriate and may be better suited than the standard elastic model: the Hookean spring. We associated Scott Blair behavior with the load-induced, quasi-instantaneous re-arrangement of polymer network chains. The secondary viscoelastic mechanism associated with the Lomnitz element, hydrogen bond breakage and rearrangement, comes into play for higher temperatures and/or higher physisorbed water contents. In this case, the contribution of the two constitutive elements is well separated due to the large number of the characteristic time of the Lomnitz element, much larger than the respective value for the Scott Blair element.

Konjac glucomannan and xanthan synergistic interaction gel: Underlying mechanism for improvement of gel mechanical properties induced by freeze-thaw treatment

Synergistic interaction gels (SIGs) formed by mixing konjac glucomannan (KGM) and xanthan at an appropriate ratio have gained increased interest due to its inherent versatility. However, their mechanical properties were not high enough to meet the needs of practical applications. This work demonstrated that freeze-thaw treatment (FT) significantly improved their mechanical properties, and the underlying mechanisms were proposed. Relative lower frozen temperature (−40 °C or −80 °C) and more freeze-thaw cycles reduced the pore size, decreased the average size of orderings (crystalline structure) and increased the ordering content (at −40 °C or under third cycle at −80 °C, except for KGM/xanthan SIGs with a ratio of KGM to xanthan at 2:8) for KGM/xanthan SIGs. Those undoubtedly increased the crosslinking density and improved the gel structure, which was responsible for the increment of G' (at 25–30 °C) and gel hardness, and reduction of water holding capacity. Freeze-thaw treatment with −15 °C did not increase the ordering contents and gel hardness, but enhanced the G' (at 25–30 °C). It is possible that freezing at −15 °C enhanced gel structure rigidity by increasing the molecular entanglement via squeezing of ice crystals and rearrangement of molecular chains. Those results are helpful to rational design and production of KGM/xanthan SIGs with physical methods.