Ligand-Directed Self-Assembly of Organic-Semiconductor/Quantum-Dot Blend Films Enables Efficient Triplet Exciton-Photon Conversion.

Blends comprising organic semiconductors and inorganic quantum dots (QDs) are relevant for many optoelectronic applications and devices. However, the individual components in organic-QD blends have a strong tendency to aggregate and phase-separate during film processing, compromising both their structural and electronic properties. Here, we demonstrate a QD surface engineering approach using electronically active, highly soluble semiconductor ligands that are matched to the organic semiconductor host material to achieve well-dispersed inorganic-organic blend films, as characterized by X-ray and neutron scattering, and electron microscopies. This approach preserves the electronic properties of the organic and QD phases and also creates an optimized interface between them. We exemplify this in two emerging applications, singlet-fission-based photon multiplication (SF-PM) and triplet-triplet annihilation-based photon upconversion (TTA-UC). Steady-state and time-resolved optical spectroscopy shows that triplet excitons can be transferred with near unity efficiently across the organic-inorganic interface, while the organic films maintain efficient SF (190% yield) in the organic phase. By changing the relative energy between organic and inorganic components, yellow upconverted emission is observed upon 790 nm NIR excitation. Overall, we provide a highly versatile approach to overcome longstanding challenges in the blending of organic semiconductors with QDs that have relevance for many optical and optoelectronic applications.

Ultrafast exciton transport at early times in quantum dot solids.

Quantum dot (QD) solids are an emerging platform for developing a range of optoelectronic devices. Thus, understanding exciton dynamics is essential towards developing and optimizing QD devices. Here, using transient absorption microscopy, we reveal the initial exciton dynamics in QDs with femtosecond timescales. We observe high exciton diffusivity (~102 cm2 s-1) in lead chalcogenide QDs within the first few hundred femtoseconds after photoexcitation followed by a transition to a slower regime (~10-1-1 cm2 s-1). QD solids with larger interdot distances exhibit higher initial diffusivity and a delayed transition to the slower regime, while higher QD packing density and heterogeneity accelerate this transition. The fast transport regime occurs only in materials with exciton Bohr radii much larger than the QD sizes, suggesting the transport of delocalized excitons in this regime and a transition to slower transport governed by exciton localization. These findings suggest routes to control the optoelectronic properties of QD solids.

Mixed Small-Molecule Matrices Improve Nanoparticle Dispersibility in Organic Semiconductor-Nanoparticle Films.

Controlling the dispersibility of nanocrystalline inorganic quantum dots (QDs) within organic semiconductor (OSC):QD nanocomposite films is critical for a wide range of optoelectronic devices. This work demonstrates how small changes to the OSC host molecule can have a dramatic detrimental effect on QD dispersibility within the host organic semiconductor matrix as quantified by grazing incidence X-ray scattering. It is commonplace to modify QD surface chemistry to enhance QD dispersibility within an OSC host. Here, an alternative route toward optimizing QD dispersibilities is demonstrated, which dramatically improves QD dispersibilities through blending two different OSCs to form a fully mixed OSC matrix phase.

Eye-tracking correlates of response to joint attention in preschool children with autism spectrum disorder.

BACKGROUND: A number of differences in joint attention behaviour between children with autism spectrum disorder (ASD) and typically developing (TD) individuals have previously been documented. METHOD: We use eye-tracking technology to assess response to joint attention (RJA) behaviours in 77 children aged 31 to 73 months. We conducted a repeated-measures analysis of variance to identify differences between groups. In addition, we analysed correlations between eye-tracking and clinical measures using Spearman's correlation. RESULTS: The children diagnosed with ASD were less likely to follow gaze compared to TD children. Children with ASD were less accurate at gaze following when only eye gaze information was available, compared to when eye gaze with head movement was observed. Higher accuracy gaze-following profiles were associated with better early cognition and more adaptive behaviours in children with ASD. Less accurate gaze-following profiles were associated with more severe ASD symptomatology. CONCLUSION: There are differences in RJA behaviours between ASD and TD preschool children. Several eye-tracking measures of RJA behaviours in preschool children were found to be associated with clinical measures for ASD diagnosis. This study also highlights the construct validity of using eye-tracking measures as potential biomarkers in the assessment and diagnosis of ASD in preschool children.

Rational synthesis of novel biocompatible thermoresponsive block copolymer worm gels.

It is well known that reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA) enables the rational design of diblock copolymer worm gels. Moreover, such hydrogels can undergo degelation on cooling below ambient temperature as a result of a worm-to-sphere transition. However, only a subset of such block copolymer worms exhibit thermoresponsive behavior. For example, PMPC26-PHPMA280 worm gels prepared using a poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC26) precursor do not undergo degelation on cooling to 6 °C (see S. Sugihara et al., J. Am. Chem. Soc., 2011, 133, 15707-15713). Informed by our recent studies (N. J. Warren et al., Macromolecules, 2018, 51, 8357-8371), we decided to reduce the mean degrees of polymerization of both the PMPC steric stabilizer block and the structure-directing PHPMA block when targeting a pure worm morphology. This rational approach reduces the hydrophobic character of the PHPMA block and hence introduces the desired thermoresponsive character, as evidenced by the worm-to-sphere transition (and concomitant degelation) that occurs on cooling a PMPC15-PHPMA150 worm gel from 40 °C to 6 °C. Moreover, worms are reconstituted on returning to 40 °C and the original gel modulus is restored. This augurs well for potential biomedical applications, which will be examined in due course. Finally, small-angle X-ray scattering studies indicated a scaling law exponent of 0.67 (≈2/3) for the relationship between the worm core cross-sectional diameter and the PHPMA DP for a series of PHPMA-based worms prepared using a range of steric stabilizer blocks, which is consistent with the strong segregation regime for such systems.

Controlling the structures of organic semiconductor-quantum dot nanocomposites through ligand shell chemistry.

Nanocrystal quantum dots (QD) functionalised with active organic ligands hold significant promise as solar energy conversion materials, capable of multiexcitonic processes that could improve the efficiencies of single-junction photovoltaic devices. Small-angle X-ray and neutron scattering (SAXS and SANS) were used to characterize the structure of lead sulphide QDs post ligand-exchange with model acene-carboxylic acid ligands (benzoic acid, hydrocinnamic acid and naphthoic acid). Results demonstrate that hydrocinnamic acid and naphthoic acid ligated QDs form monolayer ligand shells, whilst benzoic acid ligated QDs possess ligand shells thicker than a monolayer. Further, the formation of a range of nanocomposite materials through the self-assembly of such acene-ligated QDs with an organic small-molecule semiconductor [5,12-bis((triisopropylsilyl)ethynyl)tetracene (TIPS-Tc)] is investigated. These materials are representative of a wider set of functional solar energy materials; here the focus is on structural studies, and their optoelectronic function is not investigated. As TIPS-Tc concentrations are increased, approaching the solubility limit, SANS data show that QD fractal-like features form, with structures possibly consistent with a diffusion limited aggregation mechanism. These, it is likely, act as heterogeneous nucleation agents for TIPS-Tc crystallization, generating agglomerates containing both QDs and TIPS-Tc. Within the TIPS-Tc crystals there seem to be three distinct QD morphologies: (i) at the crystallite centre (fractal-like QD aggregates acting as nucleating agents), (ii) trapped within the growing crystallite (giving rise to QD features ordered as sticky hard spheres), and (iii) a population of aggregate QDs at the periphery of the crystalline interface that were expelled from the growing TIPS-Tc crystal. Exposure of the QD:TIPS-Tc crystals to DMF vapour, a solvent known to be able to strip ligands from QDs, alters the spacing between PbS-hydrocinnamic acid and PbS-naphthoic acid ligated QD aggregate features. In contrast, for PbS-benzoic acid ligated QDs, DMF vapour exposure promotes the formation of ordered QD colloidal crystal type phases. This work thus demonstrates how different QD ligand chemistries control the interactions between QDs and an organic small molecule, leading to widely differing self-assembly processes. It highlights the unique capabilities of multiscale X-ray and neutron scattering in characterising such composite materials.

Synthesis of High χ-Low N Diblock Copolymers by Polymerization-Induced Self-Assembly.

Polymerization-induced self-assembly (PISA) enables the scalable synthesis of functional block copolymer nanoparticles with various morphologies. Herein we exploit this versatile technique to produce so-called "high χ-low N" diblock copolymers that undergo nanoscale phase separation in the solid state to produce sub-10 nm surface features. By varying the degree of polymerization of the stabilizer and core-forming blocks, PISA provides rapid access to a wide range of diblock copolymers, and enables fundamental thermodynamic parameters to be determined. In addition, the pre-organization of copolymer chains within sterically-stabilized nanoparticles that occurs during PISA leads to enhanced phase separation relative to that achieved using solution-cast molecularly-dissolved copolymer chains.

Mechanistic Insights into Diblock Copolymer Nanoparticle-Crystal Interactions Revealed via in Situ Atomic Force Microscopy.

Recently, it has become clear that a range of nanoparticles can be occluded within single crystals to form nanocomposites. Calcite is a much-studied model, but even in this case we have yet to fully understand the details of the nanoscale interactions at the organic-inorganic interface that lead to occlusion. Here, a series of diblock copolymer nanoparticles with well-defined surface chemistries were visualized interacting with a growing calcite surface using in situ atomic force microscopy. These nanoparticles comprise a poly(benzyl methacrylate) (PBzMA) core-forming block and a non-ionic poly(glycerol monomethacrylate) (Ph-PGMA), a carboxylic acid-tipped poly(glycerol monomethacrylate) (HOOC-PGMA), or an anionic poly(methacrylic acid) (PMAA) stabilizer block. Our results reveal three modes of interaction between the nanoparticles and the calcite surface: (i) attachment followed by detachment, (ii) sticking to and "hovering" over the surface, allowing steps to pass beneath the immobilized nanoparticle, and (iii) incorporation of the nanoparticle by the growing crystals. By analyzing the relative contributions of these three types of interactions as a function of nanoparticle surface chemistry, we show that ∼85% of PMAA85-PBzMA100 nanoparticles either "hover" or become incorporated, compared to ∼50% of the HOOC-PGMA71-PBzMA100 nanoparticles. To explain this difference, we propose a two-state binding mechanism for the anionic PMAA85-PBzMA100 nanoparticles. The "hovering" nanoparticles possess highly extended polyelectrolytic stabilizer chains and such chains must adopt a more "collapsed" conformation prior to successful nanoparticle occlusion. This study provides a conceptual framework for understanding how sterically stabilized nanoparticles interact with growing crystals, and suggests design principles for improving occlusion efficiencies.

Corrective ventilation strategies in delivery room resuscitation of preterm infants.

AIM: Corrective ventilation strategies (CVS) during neonatal resuscitation and stabilisation (R&S) are taught through the MRSOPA mnemonic: Mask adjustment, Repositioning airway, Suctioning, Opening the mouth, Increasing inspiratory Pressure, and Alternative airway. The aim was to examine the use of CVS and to investigate the relationship between MRSOPA strategies and intubation of very preterm infants <32 weeks' gestation in the delivery room. METHODS: Retrospective review of video recordings of R&S of preterm infants born in Cork University Maternity Hospital, Ireland. RESULTS: In 46 resuscitation recordings, mask adjustment was observed in almost all (95.6%), followed by suctioning, (23.9%), opening the mouth (100%), increasing inspiratory pressure (81.0%) and intubation (32.6%). The most frequently used mask holds were: one-handed (95.6%), two-handed (63.0%), stem hold (23.8%), and modified spider hold (6.5%). There were no significant associations between individual mask holds and intubation. The more CVS employed the greater the need for intubation. CONCLUSION: The greater the number of MRSOPA strategies used in the delivery room, the more likely intubation occurred. Further studies may identify the effect of these CVS on short- and long-term outcomes, in order to enhance R&S training and clinical practice.

Increased Population Risk of AIP-Related Acromegaly and Gigantism in Ireland.

The aryl hydrocarbon receptor interacting protein (AIP) founder mutation R304* (or p.R304* ; NM_003977.3:c.910C>T, p.Arg304Ter) identified in Northern Ireland (NI) predisposes to acromegaly/gigantism; its population health impact remains unexplored. We measured R304* carrier frequency in 936 Mid Ulster, 1,000 Greater Belfast (both in NI) and 2,094 Republic of Ireland (ROI) volunteers and in 116 NI or ROI acromegaly/gigantism patients. Carrier frequencies were 0.0064 in Mid Ulster (95%CI = 0.0027-0.013; P = 0.0005 vs. ROI), 0.001 in Greater Belfast (0.00011-0.0047) and zero in ROI (0-0.0014). R304* prevalence was elevated in acromegaly/gigantism patients in NI (11/87, 12.6%, P < 0.05), but not in ROI (2/29, 6.8%) versus non-Irish patients (0-2.41%). Haploblock conservation supported a common ancestor for all the 18 identified Irish pedigrees (81 carriers, 30 affected). Time to most recent common ancestor (tMRCA) was 2550 (1,275-5,000) years. tMRCA-based simulations predicted 432 (90-5,175) current carriers, including 86 affected (18-1,035) for 20% penetrance. In conclusion, R304* is frequent in Mid Ulster, resulting in numerous acromegaly/gigantism cases. tMRCA is consistent with historical/folklore accounts of Irish giants. Forward simulations predict many undetected carriers; geographically targeted population screening improves asymptomatic carrier identification, complementing clinical testing of patients/relatives. We generated disease awareness locally, necessary for early diagnosis and improved outcomes of AIP-related disease.

Cross-phenotype association mapping of the MHC identifies genetic variants that differentiate psoriatic arthritis from psoriasis.

OBJECTIVES: Psoriatic arthritis (PsA) is a chronic inflammatory arthritis, with a strong heritable component, affecting patients with psoriasis. Here we attempt to identify genetic variants within the major histocompatibility complex (MHC) that differentiate patients with PsA from patients with cutaneous psoriasis alone (PsC). METHODS: 2808 patients with PsC, 1945 patients with PsA and 8920 population controls were genotyped. We imputed SNPs, amino acids and classical HLA alleles across the MHC and tested for association with PsA compared to population controls and the PsC patient group. In addition we investigated the impact of the age of disease onset on associations. RESULTS: HLA-C*06:02 was protective of PsA compared to PsC (p=9.57×10-66, OR 0.37). The HLA-C*06:02 risk allele was associated with a younger age of psoriasis onset in all patients (p=1.01×10-59). After controlling for the age of psoriasis onset no association of PsA to HLA-C*06:02 (p=0.07) was observed; instead, the most significant association was to amino acid at position 97 of HLA-B (p=1.54×10-9) where the presence of asparagine or serine residue increased PsA risk. Asparagine at position 97 of HLA-B defines the HLA-B*27 alleles. CONCLUSIONS: By controlling for the age of psoriasis onset, we show, for the first time, that HLA-C*06:02 is not associated with PsA and that amino acid position 97 of HLA-B differentiates PsA from PsC. This amino acid also represents the largest genetic effect for ankylosing spondylitis, thereby refining the genetic overlap of these two spondyloarthropathies. Correcting for bias has important implications for cross-phenotype genetic studies.

A Randomized Controlled Trial of End-Tidal Carbon Dioxide Detection of Preterm Infants in the Delivery Room.

OBJECTIVE: To compare the ability of qualitative versus quantitative methods of end-tidal carbon dioxide (EtCO2) detection to maintain normocarbia during face mask ventilation (FMV) of preterm infants (<32 weeks) in the delivery room. STUDY DESIGN: Preterm infants <32 weeks were randomly assigned to the use of a disposable PediCap EtCO2 detector (Covidien, Dublin, Ireland) (qualitative) or a Microstream side stream capnography device (Covidien) (quantitative) for FMV in the delivery room, via a NeoPuff T-piece resuscitator (Fisher and Paykel, Auckland, New Zealand). The primary outcome was the presence of normocarbia, based on partial pressure of CO2 (PaCO2) readings obtained in the neonatal intensive care unit within an hour of birth. Normocarbia was defined as a PaCO2 measure between 37.5 and 60 mm Hg (5-8 kPa). RESULTS: Of the 59 infants included, 59% (35/59) were within the PaCO2 target range within an hour of birth. There was no difference in the primary outcome; 64% (21/33) of infants in the quantitative group were within the PaCO2 range compared with 54% (14/26) in the qualitative group (P = .594); and 93% of participants <28 weeks' gestation were within the PaCO2 normocarbic range (90% [9/10] in quantitative group and 100% [5/5] in the qualitative group [P = 1]). There was no difference in the intubation rate, days of ventilation, or bronchopulmonary dysplasia rates between the 2 groups. CONCLUSIONS: Quantitative or qualitative EtCO2 detection methods are both feasible for FMV in the delivery room. Although there was no difference in the incidence of normocarbia, the use of either form of EtCO2 monitoring should be considered during newborn stabilization, especially in infants less than 28 weeks' gestation. TRIAL REGISTRATION: ISRCTN: ISRCTN10934870.

The Twin Evils of Concomitant Rare Pathology with Variant Anatomy: Superior Mesenteric Artery Aneurysm and a Replaced Right Hepatic Artery.

Aneurysmal degeneration of the superior mesenteric artery (SMA) is a rare clinical finding, estimated to affect <1% of the general population in postmortem studies. Due to the rare prevalence of aneurysms affecting the SMA, there are no clear or definitive published consensus guidelines for its management at presentation, with both surgical and endovascular options described. An aberrant or replaced right hepatic artery (RRHA) is thought to affect 10-15% of the population. The prevalence of both conditions presenting concomitantly is unknown, but undoubtedly even rarer. We describe the successful management of a symptomatic SMA aneurysm with an RRHA emerging from the aneurysmal sac presenting to our vascular unit. This was repaired via an open surgical approach with SMA aneurysmectomy and interposition grafting using reversed vein with preservation of RHA liver perfusion via a novel reconstruction option. This case highlights the challenge that visceral aneurysms pose, especially when simple or orthodox reconstruction options are limited due to rare or unusual anatomy.

Mycotic Aneurysm of the Extracranial Internal Carotid Artery, Resect and Ligate or Reconstruct?

Mycotic aneurysmal disease of the extracranial carotid arteries (ECA) is a rare entity associated with a high morbidity, including rupture, hemorrhage, airway obstruction, and stroke. Surgical management is challenging due to difficult dissection through infected or inflamed tissue. This report highlights a case of ECA-aneurysm infection presenting with stroke and an occluded internal carotid artery, likely due to microbial arteritis on a background of osteomyelitis. Operative intervention was performed to definitively treat the infection and prevent the potential associated complications. In this case, the incident vessel was 100% occluded at presentation, allowing vessel ligation and resection without carotid complex reconstruction.

Testing the vesicular morphology to destruction: birth and death of diblock copolymer vesicles prepared via polymerization-induced self-assembly.

Small angle X-ray scattering (SAXS), electrospray ionization charge detection mass spectrometry (CD-MS), dynamic light scattering (DLS), and transmission electron microscopy (TEM) are used to characterize poly(glycerol monomethacrylate)55-poly(2-hydroxypropyl methacrylate)x (G55-Hx) vesicles prepared by polymerization-induced self-assembly (PISA) using a reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization formulation. A G55 chain transfer agent is utilized to prepare a series of G55-Hx diblock copolymers, where the mean degree of polymerization (DP) of the membrane-forming block (x) is varied from 200 to 2000. TEM confirms that vesicles with progressively thicker membranes are produced for x = 200-1000, while SAXS indicates a gradual reduction in mean aggregation number for higher x values, which is consistent with CD-MS studies. Both DLS and SAXS studies indicate minimal change in the overall vesicle diameter between x = 400 and 800. Fitting SAXS patterns to a vesicle model enables calculation of the membrane thickness, degree of hydration of the membrane, and the mean vesicle aggregation number. The membrane thickness increases at higher x values, hence the vesicle lumen must become smaller if the external vesicle dimensions remain constant. Geometric considerations indicate that this growth mechanism lowers the total vesicle interfacial area and hence reduces the free energy of the system. However, it also inevitably leads to gradual ingress of the encapsulated water molecules into the vesicle membrane, as confirmed by SAXS analysis. Ultimately, the highly plasticized membranes become insufficiently hydrophobic to stabilize the vesicle morphology when x exceeds 1000, thus this PISA growth mechanism ultimately leads to vesicle "death".

PTPN22 is associated with susceptibility to psoriatic arthritis but not psoriasis: evidence for a further PsA-specific risk locus.

OBJECTIVES: Psoriatic arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis; it has a higher estimated genetic component than psoriasis alone, however most genetic susceptibility loci identified for PsA to date are also shared with psoriasis. Here we attempt to validate novel single nucleotide polymorphisms selected from our recent PsA Immunochip study and determine specificity to PsA. METHODS: A total of 15 single nucleotide polymorphisms were selected (PImmunochip <1×10(-4)) for validation genotyping in 1177 cases and 2155 controls using TaqMan. Meta-analysis of Immunochip and validation data sets consisted of 3139 PsA cases and 11 078 controls. Novel PsA susceptibility loci were compared with data from two large psoriasis studies (WTCCC2 and Immunochip) to determine PsA specificity. RESULTS: We found genome-wide significant association to rs2476601, mapping to PTPN22 (p=1.49×10(-9), OR=1.32), but no evidence for association in the psoriasis cohort (p=0.34) and the effect estimates were significantly different between PsA and psoriasis (p=3.2×10(-4)). Additionally, we found genome-wide significant association to the previously reported psoriasis risk loci; NOS2 (rs4795067, p=5.27×10(-9)). CONCLUSIONS: For the first time, we report genome-wide significant association of PTPN22 (rs2476601) to PsA susceptibility, but no evidence for association to psoriasis.

Effects of Fractional Inspired Oxygen on Cerebral Oxygenation in Preterm Infants following Delivery.

OBJECTIVES: To explore regional cerebral oxygen saturations (rcSO2) in preterm neonates initially stabilized with 0.3 fractionated inspired oxygen (FiO2) concentrations. We hypothesized that those infants who received >0.3 FiO2 during stabilization following delivery would have relatively higher rcSO2 postdelivery compared with those stabilized with a lower FiO2. STUDY DESIGN: A single center prospective observational study of 47 infants born before 32 weeks. Using near infrared spectroscopy, rcSO2 values were recorded immediately after birth. All preterm infants were initially given 0.3 FiO2 and were divided into 2 groups according to subsequent FiO2 requirements of either ≤0.3 or >0.3 FiO2. Using a mixed-effects model, we compared the difference between the groups over time. Also, the area measures below 55% (hypoxia) and above 85% (hyperoxia) were compared between the groups. RESULTS: The mean (SD) gestation was 29.4 (1.6) weeks and the mean (SD) weight was 1.3 (0.4) kg. Less than one-half of the infants (20/45; 43%) required ≤0.3 FiO2. In the delivery suite, the median (IQR) rcSO2 in the low and high FiO2 groups were 81% (66%-86%) and 72% (62%-86%), respectively. Patients in the high FiO2 group had a larger rcSO2 area below 55% (P = .01). There was a significant difference in rcSO2 between the groups (P < .05), with the low group having higher rcSO2 values initially, but this difference changed over time. In the neonatal intensive care unit (NICU), rcSO2 values were lower by 7.1% (CI 12.13 to 2.06%) P = .008 in the high FiO2 group. CONCLUSIONS: Infants given >0.3 FiO2 had more cerebral hypoxia than infants requiring ≤0.3 FiO2 but no difference in the degree of cerebral hyperoxia, both in the delivery suite and the NICU. This suggests that a more rapid increase in oxygen titration maybe be required initially for preterm infants.

Self-Assembly-Driven Electrospinning: The Transition from Fibers to Intact Beaded Morphologies.

Polymer beads have attracted considerable interest for use in catalysis, drug delivery, and photonics due to their particular shape and surface morphology. Electrospinning, typically used for producing nanofibers, can also be used to fabricate polymer beads if the solution has a sufficiently low concentration. In this work, a novel approach for producing more uniform, intact beads is presented by electrospinning self-assembled block copolymer (BCP) solutions. This approach allows a relatively high polymer concentration to be used, yet with a low degree of entanglement between polymer chains due to microphase separation of the BCP in a selective solvent system. Herein, to demonstrate the technology, a well-studied polystyrene-poly(ethylene butylene)-polystyrene triblock copolymer is dissolved in a co-solvent system. The effect of solvent composition on the characteristics of the fibers and beads is intensively studied, and the mechanism of this fiber-to-bead is found to be dependent on microphase separation of the BCP.