Polarization Ray Tracing and Polarization Aberration Compensation in Reflective Astronomical Telescopes

Assessing and optimizing polarization performance in the context of ray-based optical design can be challenging. We describe an approach to this problem that decouples polarization effects from optical system geometry for reflective systems. Each surface's polarization properties are parameterized in terms of their impact on retardance and diattenuation in the small angle-of-incidence limit, separating polarization assessment from the task of coating design. A low-resolution ray trace of the system is adequate to determine ray geometry at each interface, which can then be interpolated to rapidly evaluate net Jones Matrix pupil functions. Coating behavior can be easily varied using the ellipsometric parameters to investigate impacts and compensation. Desired values of these parameters can then be specified as constraints in coating design. Investigation with candidate telescope optical designs for LUVOIR show baseline root-mean-square wavefront errors in the nm range for the on-diagonal Jones matrix component, and throughputs of tens of parts per million. Promising possibilities for compensation using a purpose-designed coating on the secondary mirror are discussed, which reduce the on-diagonal wavefront error by a factor 20, with accompanying but more modest reductions in coupling into off-diagonal terms

Geography and Location Are the Primary Drivers of Office Microbiome Composition.

In the United States, humans spend the majority of their time indoors, where they are exposed to the microbiome of the built environment (BE) they inhabit. Despite the ubiquity of microbes in BEs and their potential impacts on health and building materials, basic questions about the microbiology of these environments remain unanswered. We present a study on the impacts of geography, material type, human interaction, location in a room, seasonal variation, and indoor and microenvironmental parameters on bacterial communities in offices. Our data elucidate several important features of microbial communities in BEs. First, under normal office environmental conditions, bacterial communities do not differ on the basis of surface material (e.g., ceiling tile or carpet) but do differ on the basis of the location in a room (e.g., ceiling or floor), two features that are often conflated but that we are able to separate here. We suspect that previous work showing differences in bacterial composition with surface material was likely detecting differences based on different usage patterns. Next, we find that offices have city-specific bacterial communities, such that we can accurately predict which city an office microbiome sample is derived from, but office-specific bacterial communities are less apparent. This differs from previous work, which has suggested office-specific compositions of bacterial communities. We again suspect that the difference from prior work arises from different usage patterns. As has been previously shown, we observe that human skin contributes heavily to the composition of BE surfaces. IMPORTANCE Our study highlights several points that should impact the design of future studies of the microbiology of BEs. First, projects tracking changes in BE bacterial communities should focus sampling efforts on surveying different locations in offices and in different cities but not necessarily different materials or different offices in the same city. Next, disturbance due to repeated sampling, though detectable, is small compared to that due to other variables, opening up a range of longitudinal study designs in the BE. Next, studies requiring more samples than can be sequenced on a single sequencing run (which is increasingly common) must control for run effects by including some of the same samples in all of the sequencing runs as technical replicates. Finally, detailed tracking of indoor and material environment covariates is likely not essential for BE microbiome studies, as the normal range of indoor environmental conditions is likely not large enough to impact bacterial communities

On a Summer Trip

text-and-image creation, 10 pages.Someone dies. Three friends meet; one travels from the West, another comes back to Canada, the third one welcomes them in his garden.Research Centre in Interdisciplinary Arts and Creative Culture (MIWSFPA, Brock University

Sterically restricted tin phosphines, stabilized by weak intramolecular donor-acceptor interactions

Funding: Engineering and Physical Sciences Research Council (EPSRC)Four related sterically restricted pen-substituted acenaphthenes have been prepared containing mixed tin phosphorus moieties in the proximal 5,6-positions (Acenap[SnR3][(PPr2)-Pr-i]; Acenap = acenaphthene-5,6-diyl; R-3 = Ph-3 (1), Ph2Cl (2), Me2Cl (3), Bu2Cl (4)). The degree of intramolecular P-Sn bonding within the series was investigated by X-ray crystallography, solution and solid-state NMR spectroscopy, and density functional theory (DFT/B3LYP/SBKJC/PCM) calculations. All members of the series adopt a conformation such that the phosphorus lone pair is located directly opposite the tin center, promoting an intramolecular donor acceptor P -> Sn type interaction. The extent of covalent bonding between Sn and P is found to be much greater in triorganotin chlorides 2-4 in comparison with the triphenyl derivative 1. Coordination of a highly electronegative chlorine atom naturally increases the Lewis acidity of the tin center, enhancing the Ip(P)-sigma*(Sn-Y) donor acceptor 3c-4e type interaction, as indicated by conspicuously short Sn-P peri distances and significant (1)J(P-31,Sn-119) spin spin coupling constants (SSCCs) in the range 740-754 Hz. Evidence supporting the presence of this interaction was also found in solid-state NMR spectra of some of the compounds which exhibit an indirect spin spin coupling on the same order of magnitude as observed in solution. DFT calculations confirm the increased covalent bonding between P and Sn in 2-4, with notable WBIs of ca. 0.35 obtained, in comparison to 0.1 in 1.PostprintPeer reviewe

8-Bromo­naphthalen-1-amine

The title compound, C10H8BrN, was obtained by slow addition of sodium azide to 8-bromo-1-naphthoic acid, followed by addition of aqueous ammonia. The crude product was crystallized from petroleum ether to give pink crystals. Compared to other 1,8-disubstituted naphthalene compounds, this compound exhibits less strain between the 1 and 8 substituents. Additionally, the NH protons form both intra- and inter­molecular hydrogen bonds. The naphthalene units are arranged in a herring-bone stacking motif

Platinum bisphosphine complexes of 1,8-naphthosultone

Funding: Engineering and Physical Sciences Research Council (EPSRC)A series of three platinum (II) bisphosphine complexes 1-3 [Pt(1-(SO2),8-(O)-nap)(PR3)2] (where R3 = Ph3, Ph2Me, Me2Ph) have been prepared by metathesis from cis-[Pt(PR3)2Cl2)] and the dilithium salt of 1,8-naphthosultone. The novel compounds were fully characterised by X-ray crystallography, multinuclear NMR, IR and MS. The molecular structures of 1-3 were compared by measuring the peri-distance, splay angle magnitude, peri-atom displacement, naphthalene ring torsions, aromatic ring orientations and the geometry around the platinum centre. The platinum metal adopts a distorted square planar geometry in all three complexes which causes deformation of the naphthalene system. The degree of molecular deformation does not decrease upon going from 1 to 3 as anticipated, instead a competition between steric effects and intramolecular interactions causes 3 to display distortion intermediate of 1 and 2.PostprintPeer reviewe

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