409 research outputs found
Sterically encumbered tin and phosphorus peri-substituted acenaphthenes
The work in this project was supported by the Engineering and Physical Sciences Research Council (EPSRC), EaStCHEM and the University of St Andrews.A group of sterically encumbered peri-substituted acenaphthenes have been prepared, containing tin moieties at the 5,6-positions in 1 – 3 ([Acenap(SnR3)2], Acenap = acenaphthene-5,6-diyl; R3 = Ph3 ( 1 ), Me3 ( 2 ); [(Acenap)2(SnMe2)2] ( 3 )) and phosphorus functional groups at the proximal peri-positions in 4 and 5 ([Acenap(PR2)(PiPr2)] R2 = Ph2 ( 4 ), Ph(iPr) ( 5 )). Bis(stannane) structures 1 – 3 are dominated by repulsive interactions between the bulky tin groups, leading to peri-distances approaching the sum of van der Waals radii. Conversely, the quasi-linear CPh-P···P three-body fragments found in bis(phosphine) 4 suggest the presence of a lp(P)−σ*(P–C) donor–acceptor 3c-4e type interaction, supported by a notably short intramolecular P···P distance and notably large JPP through-space coupling (180 Hz). Severely strained bis(sulfides) 4-S and 5-S , experiencing pronounced in-plane and out-of-plane displacements of the exocyclic peri-bonds, have also been isolated following treatment of 4 and 5 with sulfur. The resulting nonbonded intramolecular P···P distances, ∼4.05 Å and ∼12% longer than twice the van der Waals radii of P (3.60 Å), are among the largest ever reported peri-separations, independent of the heteroatoms involved, and comparable to the distance found in 1 containing the larger Sn atoms (4.07 Å). In addition we report two metal complexes with square planar [( 4 )PtCl2] ( 4-Pt ) and octahedral cis-[( 4 )Mo(CO)4] ( 4-Mo ) geometries. In both complexes the bis(phosphine) backbone is distorted, but notably less so than in bis(sulfide) 4-S . All compounds were fully characterized, and except for bis(phosphine) 5 , crystal structures were determined.PostprintPostprintPeer reviewe
Considering the impact of situation-specific motivations and constraints in the design of naturally ventilated and hybrid buildings
A simple logical model of the interaction between a building and its occupants is presented based on the principle that if free to do so, people will adjust their posture, clothing or available building controls (windows, blinds, doors, fans, and thermostats) with the aim of achieving or restoring comfort and reducing discomfort. These adjustments are related to building design in two ways: first the freedom to adjust depends on the availability and ease-of-use of control options; second the use of controls affects building comfort and energy performance. Hence it is essential that these interactions are considered in the design process. The model captures occupant use of controls in response to thermal stimuli (too warm, too cold etc.) and non-thermal stimuli (e.g. desire for fresh air). The situation-specific motivations and constraints on control use are represented through trigger temperatures at which control actions occur, motivations are included as negative constraints and incorporated into a single constraint value describing the specifics of each situation. The values of constraints are quantified for a range of existing buildings in Europe and Pakistan. The integration of the model within a design flow is proposed and the impact of different levels of constraints demonstrated. It is proposed that to minimise energy use and maximise comfort in naturally ventilated and hybrid buildings the designer should take the following steps: 1. Provide unconstrained low energy adaptive control options where possible, 2. Avoid problems with indoor air quality which provide motivations for excessive ventilation rates, 3. Incorporate situation-specific adaptive behaviour of occupants in design simulations, 4. Analyse the robustness of designs against variations in patterns of use and climate, and 5. Incorporate appropriate comfort standards into the operational building controls (e.g. BEMS)
A subset of myofibroblastic cancer-associated fibroblasts regulate collagen fiber elongation, which is prognostic in multiple cancers
Collagen structure has been shown to influence tumor cell invasion, metastasis and clinical outcome in breast cancer. However, it remains unclear how it affects other solid cancers. Here we utilized multi-photon laser scanning microscopy and Second Harmonic Generation to identify alterations to collagen fiber structure within the tumor stroma of head & neck, esophageal and colorectal cancers. Image segmentation algorithms were then applied to quantitatively characterize these morphological changes, showing that elongated collagen fibers significantly correlated with poor clinical outcome (Log Rank p < 0.05). We used TGF-? treatment to model fibroblast conversion to smooth muscle actin SMA-positive cancer associated fibroblasts (CAFs) and found that these cells induce the formation of elongated collagen fibers in vivo. However, proteomic/transcriptomic analysis of SMA-positive CAFs cultured ex-vivo showed significant heterogeneity in the expression of genes with collagen fibril organizing gene ontology. Notably, stratifying patients according to stromal SMA-positivity and collagen fiber elongation was found to provide a highly significant correlation with poor survival in all 3 cancer types (Log Rank p ? 0.003). In summary, we show that increased collagen fiber length correlates with poor patient survival in multiple tumor types and that only a sub-set of SMA-positive CAFs can mediate the formation of this collagen structure
CLASSY IX: The Chemical Evolution of the Ne, S, Cl, and Ar Elements
To study the chemical evolution across cosmic epochs, we investigate Ne, S,
Cl, and Ar abundance patterns in the COS Legacy Archive Spectroscopic SurveY
(CLASSY). CLASSY comprises local star-forming galaxies (0.02 < z < 0.18) with
enhanced star-formation rates, making them strong analogues to high-z
star-forming galaxies. With direct measurements of electron temperature, we
derive accurate ionic abundances for all elements and assess ionization
correction factors (ICFs) to account for unseen ions and derive total
abundances. We find Ne/O, S/O, Cl/O, and Ar/O exhibit constant trends with
gas-phase metallicity for 12+log(O/H) < 8.5 but significant correlation for
Ne/O and Ar/O with metallicity for 12+log(O/H) > 8.5, likely due to ICFs. Thus,
applicability of the ICFs to integrated spectra of galaxies could bias results,
underestimating true abundance ratios. Using CLASSY as a local reference, we
assess the evolution of Ne/O, S/O, and Ar/O in galaxies at z>3, finding no
cosmic evolution of Ne/O, while the lack of direct abundance determinations for
S/O and Ar/O can bias the interpretation of the evolution of these elements. We
determine the fundamental metallicity relationship (FMR) for CLASSY and compare
to the high-redshift FMR, finding no evolution. Finally, we perform the first
mass-neon relationship analysis across cosmic epochs, finding a slight
evolution to high Ne at later epochs. The robust abundance patterns of CLASSY
galaxies and their broad range of physical properties provide essential
benchmarks for interpreting the chemical enrichment of the early galaxies
observed with the JWST.Comment: Accepted for publication in The Astrophysical Journal. 20 pages (main
body), 10 figures, 6 Table
Using imaging to combat a pandemic:rationale for developing the UK National COVID-19 Chest Imaging Database
No abstract available
Parent-of-origin-specific allelic associations among 106 genomic loci for age at menarche.
Age at menarche is a marker of timing of puberty in females. It varies widely between individuals, is a heritable trait and is associated with risks for obesity, type 2 diabetes, cardiovascular disease, breast cancer and all-cause mortality. Studies of rare human disorders of puberty and animal models point to a complex hypothalamic-pituitary-hormonal regulation, but the mechanisms that determine pubertal timing and underlie its links to disease risk remain unclear. Here, using genome-wide and custom-genotyping arrays in up to 182,416 women of European descent from 57 studies, we found robust evidence (P < 5 × 10(-8)) for 123 signals at 106 genomic loci associated with age at menarche. Many loci were associated with other pubertal traits in both sexes, and there was substantial overlap with genes implicated in body mass index and various diseases, including rare disorders of puberty. Menarche signals were enriched in imprinted regions, with three loci (DLK1-WDR25, MKRN3-MAGEL2 and KCNK9) demonstrating parent-of-origin-specific associations concordant with known parental expression patterns. Pathway analyses implicated nuclear hormone receptors, particularly retinoic acid and γ-aminobutyric acid-B2 receptor signalling, among novel mechanisms that regulate pubertal timing in humans. Our findings suggest a genetic architecture involving at least hundreds of common variants in the coordinated timing of the pubertal transition
- …