Sequential Ring Research Articles

Toward High Capacity Molecular Communications Using Sequential Vortex Rings

Molecular signal coherence in fluid dynamic channels is severely hindered by mass, momentum, and turbulent diffusive forces. The combination of such forces causes long molecular tails, which results in severe inter-symbol-interference (ISI) and limits the achievable symbol rate. Here, we propose to modulate information symbols into stable vortex ring structures to minimize ISI. Each vortex ring can propagate approximately $100 \times $ the diameter of the transmission nozzle without losing its compact shape. First, we show that the ISI from sequential transmissions is minimal and reduces rapidly with distance after transmission. This is the opposite effect to conventional molecular puffs undergoing advection-diffusion, whereby ISI increases with distance. Second, we show that by maintaining a coherent signal structure, the signal-to-inference ratio is $211 \times $ higher over conventional puffs. Also, we demonstrate the vortex ring using a proof-of-concept prototype. The results point toward a promising pathway for higher capacity channels.

Construction of 4‐Isochromanones through Cu(OTf)2‐Catalysed Sequential C=O and C–O Bond Formation

A new strategy for the facile and efficient synthesis of 4‐isochromanones has been developed. The reaction involves a Cu(OTf)2‐catalysed sequential reaction of epoxides carrying electron‐deficient alkenes using the solvent DMSO as the oxidant. The single‐step process involves a sequential oxidative ring opening of epoxides and an oxa‐Michael addition where one new C=O bond and one new C–O bond are created. The advantages of this approach include high efficiency, a broad substrate scope, and mild conditions.

Biodegradable silica rubber core-shell nanoparticles and their stereocomplex for efficient PLA toughening

In the effort to overcome the shortcomings such as brittleness and poor mechanical stability, and increase the competitive edge of renewable poly(lactic acid) PLA over conventional petroleum-based thermoplastics, silica rubber core-shell nanoparticles for effective PLA toughening were successfully synthesized by sequential ring opening polymerization (ROP). The core-shell structure was designed with silica as inner core, P(CL-mLA) as ‘rubber’ middle layer and terminal PDLA chains (SiO2-r-PDLA), to facilitate the stereocomplex formation with PLLA matrix for enhanced interface control. The PLLA/SiO2-r-PDLA nanocomposites were fabricated through solution blending-injection molding process. Nuclear magnetic resonance (1H NMR and 13C NMR) results confirmed the presence of grafted ’rubber’ and PDLA chains from the surface of silica particle. In addition, PLLA/SiO2-r-PDLA nanocomposites showed tremendous improvement in thermal and mechanical properties using differential scanning calorimetry (DSC) and tensile testing, respectively. Besides the formation of stereocomplex in the nanocomposites, a detailed study on the melt stability of these stereocomplex nanocomposites revealed a ‘memorized’ stereocomplex behavior, i.e., having the ability to perfectly reassemble after re-crystallization from melt (melt memory effect), when rubber segment is present. Finally, structure-deformation mechanisms were studied using scanning electron microscopy (SEM) and small angle x-ray scattering (SAXS). From SAXS, crazing was clearly observed whereas SEM revealed fibrillated structures. Thus, crazing and fibrillation are the key deformation mechanisms in PLLA/SiO2-r-PDLA system. The exciting new fillers could open up new horizons for PLA advanced composites applications.

Clinical Outcomes of Sequential Intrastromal Corneal Ring Segments and an Extended Range of Vision Intraocular Lens Implantation in Patients with Keratoconus and Cataract.

Purpose To evaluate efficacy, safety, and predictability of sequential Ferrara-type intrastromal corneal ring segments (ICRS) and an extended range of vision intraocular lens (IOL) implantation in patients with keratoconus and cataract. Methods This study comprised patients with keratoconus and cataract that had ICRS implantation followed 6 months later by extended range of vision IOL implantation. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and residual refractive errors, analysed using vector analysis, were recorded preoperatively, 6 months after ICRS implantation, and 6 months after IOL implantation, respectively. Results The study enrolled 17 eyes (11 patients). The mean UDVA (logMAR scale) was 1.15 ± 0.67 preoperatively, 0.88 ± 0.69 six months after ICRS implantation (P = 0.005), and 0.27 ± 0.18 six months after IOL implantation (P < 0.0001). The CDVA changed from 0.26 ± 0.15 (logMAR) before surgery to 0.17 ± 0.08 six months after Ferrara-type ICRS implantation (P = 0.002) and to 0.07 ± 0.06 six months after IOL implantation (P < 0.0001). The spherical equivalent and the refractive cylinder declined steeply after IOL implantation (P < 0.001). The magnitude of depth of focus was 2.60 ± 1.02 D. There were no statistically significant differences in visual acuity for a defocus range from +0.50 D to −0.50 D (P > 0.1). Conclusion Sequential Ferrara-type ICRS and an extended range of vision IOL implantation provided good visual and refractive outcomes, being an effective, safe, and predictable procedure for the treatment of selected cases of patients with keratoconus and cataract. In addition, this approach provides an increase of tolerance to defocus.

Does Level-k Behavior Imply Level-k Thinking?

The level-k literature classifies subjects into different Lk types by their observed levels of reasoning in games. However, it remains unclear whether the observed level-k behavior is determined by belief or reasoning ability. This study proposes a strategy to identify the ability-bounded Lk subjects, who could not reason more than k steps of iterated best responses and thus have reached the upper bound of their reasoning capacity. The identification utilizes a combination of simultaneous and sequential ring games. In the sequential games, it requires an extra reasoning step to best respond as Lk, and thus the ability-bounded ones would fail the task. Results show that more than half of the L2 and L3 subjects are ability-bounded. Additionally, subjects' CRT scores, a measure of their cognitive ability, support the separation of these types. The findings suggest that both belief and reasoning ability could determine the observed levels, and thus one must be cautious when trying to infer belief or ability from the existing level-k data.

Toric ICL Implantation After Sequential Intracorneal Ring Segments Implantation and Corneal Cross-linking in Keratoconus: 2-Year Follow-up.

To evaluate 6-month and 2-year safety and clinical outcomes of Visian toric Implantable Collamer Lens (toric ICL) (STAAR Surgical, Monrovia, CA) implantation for the treatment of residual refractive errors after sequential intracorneal ring segments (ICRS) insertion and cross-linking (CXL) in keratoconus. This consecutive case series included the results of a three-step ICRS-CXL-toric ICL procedure in 16 eyes of 13 patients with moderate to severe keratoconus (stages II and III of Amsler-Krumeich classification). The ICRS and CXL procedures were performed sequentially with an interval of 4 weeks and the toric ICL implantation was performed at least 6 months after CXL. Data were collected preoperatively, at 6 months after sequential ICRS-CXL, and at 6 and 24 months following toric ICL implantation. All 16 eyes were evaluated at the 2-year follow-up. There was a significant decrease in keratometry (steep, flat, and maximum) and refraction (sphere and spherical equivalence, but not cylinder) and a significant increase in both uncorrected (UDVA) (from 1.06 to 0.76 logMAR, P = .004) and corrected (CDVA) (from 0.42 to 0.26 logMAR; P = .002) distance visual acuity 6 months following sequential ICRS-CXL, whereas UDVA and refraction significantly improved 6 months after ICL insertion (UDVA reached 0.33 logMAR, P = .001). At the 24-month follow-up, UDVA and keratometric readings were stable, whereas CDVA, sphere, and cylinder showed a significant improvement. Implantation of Visian toric ICL following sequential ICRS insertion and CXL is an effective and safe option for correcting high residual refractive error and improving visual acuity in patients with moderate to severe keratoconus in the long term. [J Refract Surg. 2017;33(9):610-616.].

Lewis Acid‐Catalyzed [4+2] Annulation between Propargylic Alcohols with Benzo[d]isoxazoles

AbstractAn unprecedented copper(II) trifluoromethanesulfonate‐catalyzed [4+2] cascade annulation of propargylic alcohols with benzo[d]isoxazoles proceeds through a sequential ring opening/Meyer–Schuster rearrangement/intermolecular cyclization. This protocol, which tolerates a broad variety of functional groups, offers a versatile, modular and atom‐economical access to a new class of fascinating quinoline derivatives in good yields under mild conditions. The transformation could be scaled up to a gram scale efficiently, thus highlighting the synthetic utility of this methodology.magnified image

Safety and Efficacy of Sequential Intracorneal Ring Segment Implantation and Cross-linking in Pediatric Keratoconus

To evaluate the safety and visual outcome of intracorneal ring segment (ICRS) implantation followed by cross-linking in pediatric keratoconus patients. Retrospective interventional case series. This retrospective study included pediatric patients (aged ≤14 years) with keratoconus and poor corrected distance visual acuity (CDVA) that underwent ICRS implantation and cross-linking (CXL). ICRS were inserted under topical anesthesia after creating a corneal tunnel with a femtosecond laser. Cross-linking was performed 1month subsequently. Records were reviewed and data collected preoperatively and at 6months, 1 year, 2 years, and 4 years postoperatively. Twelve patients (17 eyes; 10 male, 2 female) aged 9-14 years (mean age 12.3 years) received ICRS implantation followed by CXL. Follow-up times ranged from 6months to 4 years after surgery. At the 6-month follow-up all eyes were evaluated; at the 1-year, 2-year, and 4-year follow-up 11, 10, and 7 eyes were evaluated, respectively. At the 6-month follow-up, mean CDVA in comparison to preoperative levels improved significantly (P= .001) from 0.30 ± 0.19 logMAR to 0.12 ± 0.1 logMAR; mean uncorrected distance visual acuity (UDVA) also improved significantly from 0.90 ± 0.50 logMAR to 0.43 ± 0.31 logMAR. A significant decrease in both keratometry readings and spherical equivalent (from-4.0 to-1.56 diopters) was also noted after ICRS insertion. At the 1-year, 2-year, and 4-year follow-up refractive values remained relatively stable in comparison to the 6-month follow-up, except for a minor but significant improvement in cylinder and, at 4 years, in UDVA. All patients tolerated the surgery well andnointraoperative or postoperative complications were reported, except for 1 ring segment that had to be removed after 2 years owing to vascularization and corneal thinning. ICRS implantation is a safe and effective procedure for visual rehabilitation in children with keratoconus and poor CDVA.

Identification of woodland management practices and tree growth conditions in archaeological fuel waste remains: A case study from the site of Çatalhöyük in central Anatolia, Turkey

This paper presents the results of dendroanthracological analyses conducted on the anthracological assemblage retrieved from Neolithic and Chalcolithic occupations excavated at Çatalhöyük (central Anatolia, Turkey). Besides standard botanical identification of the charcoal macroremains, a range of anatomical features were also recorded including the presence of fungal decay, traumatic growth, tyloses and discontinuous growth rings. The qualitative assessment of growth ring curvature (following Marguerie and Hunot, 2007) was supplemented by quantitative estimations of minimum wood diameter (following Paradis et al., 2013) alongside sequential ring width measurements. Botanical identifications, dendroanthracological features and quantitative measurements obtained from individual charcoal fragments, were analysed using multivariate statistical techniques. These permitted assessing the relative importance of wood size, type and species in prehistoric fuel selection, and obtaining a detailed view of environmental and management impacts on prehistoric woodland growth conditions. The results of this work indicate the deep antiquity of woodland management practices in the semi-arid continental regions of Southwest Asia dating as early as the Neolithic period.

Coherent structures in interacting vortex rings

Broadly consistent with linear stability analyses, experiments find that highly organized nonlinear structures with clear azimuthal wave number emerge as sequential vortex rings are shed from a sinusoidally oscillating ellipsoidal disk.

Sequential intrastromal corneal ring segment and monofocal intraocular lens implantation for keratoconus and cataract: Long-term follow-up

To evaluate the efficacy, safety, predictability, and stability of sequential Ferrara intrastromal corneal ring segment (ICRS) and intraocular lens (IOL) implantation in patients with keratoconus and cataract. Fernández-Vega Ophthalmological Institute, Oviedo, Spain. Retrospective case series. This study comprised patients with keratoconus and cataract who had ICRS implantation followed 6months later by IOL implantation. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities and residual refractive errors, analyzed using vector analysis, were recorded preoperatively, 6months after ICRS implantation, 6months after IOL implantation, and 3years and 5years thereafter. Seventy eyes of 47 patients were studied. The mean UDVA was 1.08 logMAR ± 0.24 (SD) preoperatively, 0.95±0.31 logMAR 6months after ICRS implantation (P=.03), and 0.44±0.29 logMAR 6months after IOL implantation (P<.0001). The mean CDVA changed from 0.35±0.23 logMAR before surgery to 0.28±0.22 logMAR 6months after ICRS implantation (P<.0001) and to 0.11±0.16 logMAR 6months after IOL implantation (P<.0001). The UDVA and CDVA were stable over the period after the second procedure (P>.05). The spherical equivalent (SE) and the refractive cylinder declined steeply after IOL implantation (P<.001) and then were stable (P>.05). Sequential ICRS and IOL implantation provided good visual and refractive outcomes and was an effective, safe, predictable, and stable procedure for the treatment of patients with keratoconus and cataract.

Triblock copolymers based on ε-caprolactone and trimethylene carbonate for the 3D printing of tissue engineering scaffolds.

Biodegradable PCL-b-PTMC-b-PCL triblock copolymers based on trimethylene carbonate (TMC) and ε-caprolactone (CL) were prepared and used in the 3D printing of tissue engineering scaffolds. Triblock copolymers of various molecular weights containing equal amounts of TMC and CL were prepared. These block copolymers combine the low glass transition temperature of amorphous PTMC (approximately -20°C) and the semi-crystallinity of PCL (glass transition approximately -60°C and melting temperature approximately 60°C). PCL-b-PTMC-b-PCL triblock copolymers were synthesized by sequential ring opening polymerization (ROP) of TMC and ε-CL. From these materials, films were prepared by solvent casting and porous structures were prepared by extrusion-based 3D printing. Films prepared from a polymer with a relatively high molecular weight of 62 kg/mol had a melting temperature of 58°C and showed tough and resilient behavior, with values of the elastic modulus, tensile strength and elongation at break of approximately 120 MPa, 16 MPa and 620%, respectively. Porous structures were prepared by 3D printing. Ethylene carbonate was used as a crystalizable and water-extractable solvent to prepare structures with microporous strands. Solutions, containing 25 wt% of the triblock copolymer, were extruded at 50°C then cooled at different temperatures. Slow cooling at room temperature resulted in pores with widths of 18 ± 6 μm and lengths of 221 ± 77 μm, rapid cooling with dry ice resulted in pores with widths of 13 ± 3 μm and lengths of 58 ± 12 μm. These PCL-b-PTMC-b-PCL triblock copolymers processed into porous structures at relatively low temperatures may find wide application as designed degradable tissue engineering scaffolds. In this preliminary study we prepared biodegradable triblock copolymers based on 1,3-trimethylene carbonate and ε-caprolactone and assessed their physical characteristics. Furthermore, we evaluated their potential as melt-processable thermoplastic elastomeric biomaterials in 3D printing of tissue engineering scaffolds.

One-pot synthesis of PLA-b-PHEA via sequential ROP and RAFT polymerizations

A block copolymer library of polylactide and poly(2-hydroxyethyl acrylate) was prepared via sequential ring opening polymerization and RAFT polymerization in a one-pot approach.

Regioselective O-Sulfonylation of N,N-Bis(2-hydroxyalkyl)tosylamides as a Synthetic Key Step to Enantiopure Morpholines.

The synthesis of enantiopure 2,6-disubstituted morpholines was realized through sequential ring opening of two different optically pure oxiranes by a tosylamide, under solid-liquid phase-transfer catalysis (SL-PTC) conditions, mono-O-sulfonylation of the resulting tosylamido-2,2'-diol, and cyclization to the morpholine. The crucial step, the regioselective formation of the monosulfonate, was controlled by taking advantage of the different stereo, electronic, and coordination properties of the oxirane-derived side chains in the diol backbone. As an application of this protocol, a new morpholine-3-carboxamide was synthesized starting from threonine.

Dereplication of Flavonoid Glycoconjugates from Adenocalymma imperatoris-maximilianii by Untargeted Tandem Mass Spectrometry-Based Molecular Networking.

The interpretation of large datasets acquired using high performance liquid chromatography coupled with tandem mass spectrometry represents one of the major challenges in natural products research. Here we propose the use of molecular networking to rapid identify the known secondary metabolites from untargeted MS/MS analysis of Adenocalymma imperatoris-maximilianii plant extracts. The leaves, stems and roots of A.imperatoris-maximilianii were extracted using different solvents according to Snyder selectivity triangle. The samples were analyzed by HPLC coupled with ion trap mass spectrometer in a collision-induced dissociation MS/MS configuration in both positive and negative electrospray ionization modes. Molecular networking simultaneously organized the spectra by cosine similarity. The chemical identification was performed based on the systematic study of the main fragmentation pathways observed for the resulting network. The untargeted tandem mass spectrometry-based molecular networking allowed for the identification of 63 metabolites, mainly mono-, di- and tri-, C- and/or O-glycosyl flavones. Molecular networking was capable not only to dereplicate known flavonoids, but also to point out related prenyl derivatives, described for the first time in Adenocalymma species. The gas-phase reaction route to form the characteristic [M-H2O-(30/60/90)]+ fragments in C-glycosyl flavones was suggested as sequential sugar ring opening followed by retro-aldol elimination involving aldose-ketose isomerization. The use of molecular networking with LC-CID-MS/MS assisted the identification of various isomeric and isobaric flavonoid glycoconjugates by establishing clusters according to the fragmentation similarities. Additionally, the proposed cross-ring sugar cleavages can contribute to the identification of C-glycosides by MS/MS analysis.

Miktoarm star copolymers from D-(−)-salicin core aggregated into dandelion-like structures as anticancer drug delivery systems: synthesis, self-assembly and drug release

The β-glucoside-based heterofunctional initiator was used in the synthesis of well-defined eight-armed miktopolymers by sequential ring opening polymerization (ROP) of ε-caprolactone (CL) and atom transfer radical (co)polymerization (ATRP) of methyl methacrylate (MMA) and/or tert-butyl methacrylate (tBMA). Consequently, methacrylic acid (MAA) repeating units were introduced via selective cleavage of pendant tert-butyl protecting groups. Both the amphiphilic copolymers and miktoarm copolymers were self-assembled at 37°C and pH 7.4. The aggregates of miktoarm polymers were larger than that formed by polymethacrylate homoarm stars (≥250nm vs ≤200nm). The critical aggregation concentrations (CAC) of (mikto)stars were relatively low (0.006–0.411mg/mL) and decreased with the increase in MAA fraction content. Both MAA-based mikto- and homoarmed (co)polymers with shorter arms exhibited lower doxorubicin (DOX) loading capacity, whereas camptothecin (CPT) was encapsulated preferably by miktostars. The kinetic profiles of drug release showed that the rate of release was higher at acidic environment (pH 5.0) than in neutral pH. In the most cases the studied miktopolymer systems demonstrated the well-controlled delivery of the model anticancer drugs, which can be adjusted by structural parameters of polymeric carriers.

Gold-Catalyzed Synthesis of Quinolines from Propargyl Silyl Ethers and Anthranils through the Umpolung of a Gold Carbene Carbon.

A gold-catalyzed cascade annulation of propargylic silyl ethers with anthranils proceeds through a sequential ring opening/1,2-H-shift/protodeauration/Mukaiyama aldol cyclization. This method offers a regiospecific and modular access to 2-aminoquinolines and other quinoline derivatives under mild conditions and with a broad functional-group tolerance. The conversion is possible on a gram scale, which underlines the synthetic practicability of this methodology. The versatility of the obtained scaffold has been demonstrated by useful postfunctionalization.

Versatile design of amphiphilic glycopolypeptides nanoparticles for lectin recognition

The understanding of glycopolymer-based nanostructures formation and their lectin binding properties are of great interest to the development of drug delivery systems and other biological applications. Herein, glycosylated polypeptides were synthesized from a clickable poly(l-lysine)-b-poly(benzyl-l-glutamate) copolypeptide, obtained by a sequential ring opening polymerization. The clickable poly(l-lysine) chain was completely functionalized by introducing galactose and lactose moieties on the copolypeptide's hydrophilic block, aiming specific lectin recognition. Spheres, pearl-necklace and worm-like structures prepared from poly(l-lysine)-b-poly(benzyl-l-glutamate) copolypeptides were obtained after nanoprecipitation, depending on the hydrophilic block functionalization and the hydrophobic block length. Specific interaction between the sugars on the micelles' surface with RCA120 lectin was observed with the PBLG40-based nano-structures. However, unexpected and unspecific interactions were observed with some nanostructures, showing the importance of the chemical functionalization and nanostructure stabilization. Such a synthetic approach can be used to develop any other amphiphilic and biofunctional polypeptide-based copolymers and nanoparticles.

Enhanced Hydrodeoxygenation of m-Cresol over Bimetallic Pt–Mo Catalysts through an Oxophilic Metal-Induced Tautomerization Pathway

Supported bimetallic catalysts consisting of a noble metal (e.g., Pt) and an oxophilic metal (e.g., Mo) have received considerable attention for the hydrodeoxygenation of oxygenated aromatic compounds produced from biomass fast pyrolysis. Here, we report that PtMo can catalyze m-cresol deoxygenation via a pathway involving an initial tautomerization step. In contrast, the dominant mechanism on monometallic Pt/Al2O3 was found to be sequential Pt-catalyzed ring hydrogenation followed by dehydration on the support. Bimetallic Pt10Mo1 and Pt1Mo1 catalysts were found to produce the completely hydrogenated and deoxygenated product, methylcyclohexane (MCH), with much higher yields than monometallic Pt catalysts with comparable metal loadings and surface areas. Over an inert carbon support, MCH formation was found to be slow over monometallic Pt catalysts, while deoxygenation was significant for PtMo catalysts even in the absence of an acidic support material. Experimental studies of m-cresol deoxygenation togeth...

Transition metal free intramolecular approach for the synthesis of cyclopenta[b]chromene derivatives from phenol substituted fulvene derived azabicyclic olefins

A facile route towards the synthesis of cyclopentene fused chromene derivatives from strained phenol substituted fulvene derived bicyclic hydrazines is described. The reaction is proceeding through base catalyzed sequential intramolecular ring opening and ring closure of azabicyclic olefins. The transition metal free method provides an easy access to biologically relevant fused chromene ring system under relatively mild reaction conditions.