Free Space Optical Link Utilizing a Modulated Retro-Reflector Intended for Planetary Duplex Communication Links Between an Orbiter and Surface Unit

Presented are simulation and experimental results that provide duplex optical-free space communication links with minimal power and pointing requirements by using a modulated retro-reflector (MRR) for planetary communications. The design is the MRR resides on the surface of a planet or moon, where energy is scarce, while the source of the communication laser resides on an orbiter to achieve satellite-to-ground communications. Also, a simulated scenario using the Mars Reconnaissance Orbiter (MRO) is provided for real world potential results. The information sent through this communication path can range from raw scientific data to multimedia files such as videos and pictures. Bidirectional communications is established with the MRR by using a nested pulse position modulation (PPM) structure. This modulation scheme is then evaluated for its validity in a proof-of-concept experiment. Initial results indicate a promising return-link performance of at least 300 kbps in the nested arrangement

Synthesis of neutral nickel catalysts for ethylene polymerization – the influence of ligand size on catalyst stability

A facile synthesis of nickel salicylaldimine complexes with labile dissociating ligands is described. In addition to producing highly active ethylene polymerization catalysts, important insights into the effect of ligand size on catalyst stability and information on the mechanism of polymerization are provided

Factors Dictating Carbene Formation at (PNP)Ir

The mechanistic subtleties involved with the interaction of an amido/bis(phosphine)-supported (PNP)Ir fragment with a series of linear and cyclic ethers have been investigated using density functional theory. Our analysis has revealed the factors dictating reaction direction toward either an iridium-supported carbene or a vinyl ether adduct. The (PNP)Ir structure will allow carbene formation only from accessible carbons α to the ethereal oxygen, such that d electron back-donation from the metal to the carbene ligand is possible. Should these conditions be unavailable, the main competing pathway to form vinyl ether can occur, but only if the (PNP)Ir framework does not sterically interfere with the reacting ether. In situations where steric hindrance prevents unimpeded access to both pathways, the reaction may progress to the initial C−H activation but no further. Our mechanistic analysis is density functional independent and whenever possible confirmed experimentally by trapping intermediate species experimentally. We have also highlighted an interesting systematic error present in the DFT analysis of reactions where steric environment alters considerably within a reaction

End Capping Ring-Opening Olefin Metathesis Polymerization Polymers with Vinyl Lactones

The selective placement of a functional group at the chain end of a ring-opening metathesis polymer using ruthenium carbene initiators has been a significant limitation. Here we demonstrate a highly effective and facile end-capping technique for ROMP with living ruthenium carbene chain ends using single-turnover olefin metathesis substrates. Vinylene carbonate and 3H-furanone are introduced as functionalization and termination agents for the ruthenium-initiated ring-opening metathesis polymerization. This leads directly to the formation of functional polymer end groups without further chemical transformation steps. Aldehyde and carboxylic acid end groups can be introduced by this new method which involves the decomposition of acyl carbenes to ruthenium carbides. The high degrees of chain-end functionality obtained are supported by ^1H NMR spectroscopy, MALDI-ToF mass spectrometry, and end-group derivatization

Synthesis of coumarins by ring-closing metathesis

Investigations into olefin ring-closing metathesis (RCM) have led to a general method for the synthesis of coumarins. Catalysts with higher activity, such as the second-generation ruthenium catalyst, promote the intramolecular reaction between two-electron deficient olefins. This method allows for convenient access to a variety of coumarins substituted at both the 3- and 4-positions, as well as a tetrasubstituted example

Spiritual Struggles among Atheists: Links to Psychological Distress and Well-Being

Religious and spiritual struggles (R/S struggles)—tension or conflicts regarding religious or spiritual matters—have been robustly linked to greater psychological distress and lower well-being. Most research in this area has relied on samples consisting predominantly of participants who believe in god(s). Limited research has examined R/S struggles among atheists, generally conflating them with agnostics and other nontheists. This study investigated the prevalence of R/S struggles among atheists and compared atheists to theists in two samples (3978 undergraduates, 1048 Internet workers). Results of a multilevel model showed that atheists experience less demonic, doubt, divine, moral, and overall R/S struggles than theists, but similar levels of interpersonal and ultimate meaning struggles. Correlation and regression analyses among atheists demonstrated links between moral, ultimate meaning, and overall R/S struggles and greater distress (depression and anxiety symptoms) as well as lower well-being (life satisfaction and meaning in life). Even after controlling neuroticism, ultimate meaning struggles continued to predict lower well-being and higher distress across samples; moral struggles also predicted distress independently. This study demonstrates the relevance of R/S struggles to atheists and reinforces the applicability of previous results to atheist samples, but also highlights substantial differences between atheists and theists in certain R/S struggles