Expression of catalytic mutants of the mtDNA helicase Twinkle and polymerase POLG causes distinct replication stalling phenotypes.

The mechanism of mitochondrial DNA replication is a subject of intense debate. One model proposes a strand-asynchronous replication in which both strands of the circular genome are replicated semi-independently while the other model proposes both a bidirectional coupled leading- and lagging-strand synthesis mode and a unidirectional mode in which the lagging-strand is initially laid-down as RNA by an unknown mechanism (RITOLS mode). Both the strand-asynchronous and RITOLS model have in common a delayed synthesis of the DNA-lagging strand. Mitochondrial DNA is replicated by a limited set of proteins including DNA polymerase gamma (POLG) and the helicase Twinkle. Here, we report the effects of expression of various catalytically deficient mutants of POLG1 and Twinkle in human cell culture. Both groups of mutants reduced mitochondrial DNA copy number by severe replication stalling. However, the analysis showed that while induction of POLG1 mutants still displayed delayed lagging-strand synthesis, Twinkle-induced stalling resulted in maturated, essentially fully double-stranded DNA intermediates. In the latter case, limited inhibition of POLG with dideoxycytidine restored the delay between leading- and lagging-strand synthesis. The observed cause-effect relationship suggests that Twinkle-induced stalling increases lagging-strand initiation events and/or maturation mimicking conventional strand-coupled replication

Getting the best of you for nothing: casual voices in the Australian Academy

This research was supported by the National Recruitment funding of the NTEU. Its aim was to undertake an in-depth qualitative study of the experiences of casual academic staff in an Australian University, particularly, long-serving casual staff. The study complements the sector-wide survey study conducted by Anne Junor (2004) which looked at casual and fixed term academic and general staff in Australian universities

Addressing spin transitions on 209Bi donors in silicon using circularly-polarized microwaves

Over the past decade donor spin qubits in isotopically enriched $^{28}$Si have been intensely studied due to their exceptionally long coherence times. More recently bismuth donor electron spins have become popular because Bi has a large nuclear spin which gives rise to clock transitions (first-order insensitive to magnetic field noise). At every clock transition there are two nearly degenerate transitions between four distinct states which can be used as a pair of qubits. Here it is experimentally demonstrated that these transitions are excited by microwaves of opposite helicity such that they can be selectively driven by varying microwave polarization. This work uses a combination of a superconducting coplanar waveguide (CPW) microresonator and a dielectric resonator to flexibly generate arbitrary elliptical polarizations while retaining the high sensitivity of the CPW

Avian visual ecologists should consider UV absorbance and all sensory modalities: A response to Wisenden et al. (2020)

In a recent publication, Wisenden et al. (2020) examined responses of territorial male Red-winged Blackbirds (Agelaius phoeniceus) to models constructed with ultraviolet (UV)-reflective red epaulets for the purpose of determining if the addition of UV reflectance to epaulets ( UV+ ) changed the effectiveness of signals to receivers relative to control epaulets under field conditions. The authors hypothesized that UV+epaulet coloration represents a visual signal with increased efficacy in territorial interactions. They presented behavioral data but no visual modeling data. Our aims in this commentary are to suggest alternative terms to those used by the authors, to express concern about the use of sunscreen to manipulate the UV condition of surfaces, and to make a plea for additional data collection in future studies of avian visual ecology. The terms UV+ and UV- should be reserved for studies that create environments free from UV radiation for comparison with environments that include UV radiation. We believe that commercial sunscreens are not an appropriate choice for altering the UV conditions of surfaces presented during behavioral trials because they potentially introduce confounding influences from other sensory inputs or irritation of peripheral nerves. Wisenden et al. altered the UV absorbance of their sunscreen-treated models but did not present absorbance spectra and may not have collected those data. We acknowledge that the lack of absorbance spectra is not unusual. We implore any such future studies to collect absorbance spectra of treated and control surfaces so that those data may be used to improve visual models for UV-sensitive animals. Los ec´ologos visuales de aves deben considerer la absorbencia UV y todas las modalidades sensoriales: respuesta a Wisenden et al. (2020) RESUMEN (Spanish)—En una publicaci´on reciente, Wisenden et al. (2020) examinaron las respuestas de machos territoriales del tordo Agelaius phoeniceus a modelos construidos con charreteras rojas reflejantes ultravioletas (UV) con el prop´osito de determinar si la adici´on de reflectancia a las charreteras (‘‘UVþ’’) cambiaba la efectividad de las se˜nales dirigidas a receptores en relaci´on con charreteras ‘‘control’’ bajo condiciones de campo. Los autores ten´ıan la hip´otesis de que ‘‘la coloraci´on UVþde las charreteras representa una se˜nal visual con eficacia aumentada en interacciones territoriales’’. Los autores presentaron datos conductuales pero no datos de modelado visual. Nuestra meta en este comentario es sugerir t´erminos alternativos a aquellos empleados por los autores, expresar preocupaci´on por el uso de bloqueador solar para manipular la condici´on UV de superficies y hacer un llamado para la colecta de datos adicionales en futuros estudios de ecolog´ıa visual aviar. Los t´erminos UVþy UV– deben estar reservados para comparaciones con ambientes que incluyan radiaci´on UV. Pensamos que el uso de bloqueadores solares comerciales no es una elecci´on adecuada para la alteraci´on de las condiciones UV de superficies durante pruebas de comportamiento porque podr´ıan introducir influencias confusas provenientes de otras se˜nales sensoriales o irritar nervios perif´ericos. Wisenden et al. alteraron la absorbencia UV de sus modelos tratados con bloqueador solar pero no presentaron espectros de absorbencia y podr´ıan no haber colectado esos datos. Reconocemos que la carencia de espectros de absorbencia no es inusual. Pedimos que cualquier estudio futuro colecte espectros de absorbencia en superficies tratadas y controles para que esos datos puedan ser usados para mejorar los modelos visuales de animales sensibles a UV

Lightweight Ceramics for Aeroacoustic Applications

The use of a HTP (High Temperature Performance) ceramic foam for aeroacoustic applications is investigated. HTP ceramic foam is a composition of silica and alumina fibers developed by LMMS. This foam is a lightweight high-temperature fibrous bulk material with small pore size, ultra high porosity, and good strength. It can be used as a broadband noise absorber at both room and high temperature (up to 1800 F). The investigation included an acoustic assessment as well as material development, and environmental and structural evaluations. The results show that the HTP ceramic foam provides good broadband noise absorbing capability and adequate strength when incorporating the HTP ceramic foam system into a honeycomb sandwich structure. On the other hand, the material is sensitive to Skydrol and requires further improvements. Good progress has been made in the impedance model development. A relationship between HTP foam density, flow resistance, and tortuosity will be established in the near future. Additional effort is needed to investigate the coupling effects between face sheet and HTP foam material