Temperature Dependence of Exciton Diffusion in Conjugated Polymers

The temperature dependence of the exciton dynamics in a conjugated polymer is studied using time-resolved spectroscopy. Photoluminescence decays were measured in heterostructured samples containing a sharp polymer-fullerene interface, which acts as an exciton quenching wall. Using a 1D diffusion model, the exciton diffusion length and diffusion coefficient were extracted in the temperature range of 4-293 K. The exciton dynamics reveal two temperature regimes: in the range of 4-150 K, the exciton diffusion length (coefficient) of ~3 nm (~1.5 × 10-4 cm2/s) is nearly temperature independent. Increasing the temperature up to 293 K leads to a gradual growth up to 4.5 nm (~3.2 × 10-4 cm2/s). This demonstrates that exciton diffusion in conjugated polymers is governed by two processes: an initial downhill migration toward lower energy states in the inhomogenously broadened density of states, followed by temperature activated hopping. The latter process is switched off below 150 K.

Nonviral Approaches for Neuronal Delivery of Nucleic Acids

The delivery of therapeutic nucleic acids to neurons has the potential to treat neurological disease and spinal cord injury. While select viral vectors have shown promise as gene carriers to neurons, their potential as therapeutic agents is limited by their toxicity and immunogenicity, their broad tropism, and the cost of large-scale formulation. Nonviral vectors are an attractive alternative in that they offer improved safety profiles compared to viruses, are less expensive to produce, and can be targeted to specific neuronal subpopulations. However, most nonviral vectors suffer from significantly lower transfection efficiencies than neurotropic viruses, severely limiting their utility in neuron-targeted delivery applications. To realize the potential of nonviral delivery technology in neurons, vectors must be designed to overcome a series of extra- and intracellular barriers. In this article, we describe the challenges preventing successful nonviral delivery of nucleic acids to neurons and review strategies aimed at overcoming these challenges

Destructive disinfection of infected brood prevents systemic disease spread in ant colonies

In social groups, infections have the potential to spread rapidly and cause disease outbreaks. Here, we show that in a social insect, the ant Lasius neglectus, the negative consequences of fungal infections (Metarhizium brunneum) can be mitigated by employing an efficient multicomponent behaviour, termed destructive disinfection, which prevents further spread of the disease through the colony. Ants specifically target infected pupae during the pathogen’s non-contagious incubation period, utilising chemical ‘sickness cues’ emitted by pupae. They then remove the pupal cocoon, perforate its cuticle and administer antimicrobial poison, which enters the body and prevents pathogen replication from the inside out. Like the immune system of a metazoan body that specifically targets and eliminates infected cells, ants destroy infected brood to stop the pathogen completing its lifecycle, thus protecting the rest of the colony. Hence, in an analogous fashion, the same principles of disease defence apply at different levels of biological organisation

Figure 4–Source Data

All data from behavioural experiments associated with Figure 4 that show destructive disinfection behaviour in the ant Lasius neglectus prevents infections of the fungal pathogen Metarhizium brunneum transmitting from sick pupae to new hosts

Figure 2–Source Data for resubmission

All data from chemical and behavioural experiments associated with Figure 2 (including Figure Supplements) showing that ants use chemical cues to detect infections. Includes GC-MS data that quantitatively and qualitatively describe the cuticular chemical profiles of Lasius neglectus ant pupae exposed and infected with the fungal pathogen Metarhizium brunneum, compared to non-infected pupae. This new filed is updated to include the data associated with Figure 2-figure supplement 3-4

Data from: Destructive disinfection of infected brood prevents systemic disease spread in ant colonies

In social groups, infections have the potential to spread rapidly and cause disease outbreaks. Here, we show that in a social insect, the ant Lasius neglectus, the negative consequences of fungal infections (Metarhizium brunneum) can be mitigated by employing an efficient multicomponent behaviour, termed destructive disinfection, which prevents further spread of the disease through the colony. Ants specifically target infected pupae during the pathogen’s non-contagious incubation period, utilising chemical ‘sickness cues’ emitted by pupae. They then remove the pupal cocoon, perforate its cuticle and administer antimicrobial poison, which enters the body and prevents pathogen replication from the inside out. Like the immune system of a metazoan body that specifically targets and eliminates infected cells, ants destroy infected brood to stop the pathogen completing its lifecycle, thus protecting the rest of the colony. Hence, in an analogous fashion, the same principles of disease defence apply at different levels of biological organisation

Figure 1–Source Data

All observational and experimantal data associated with Figure 1 (including Figure Supplements) that characterise destructive disinfection behaviour in the ant Lasius neglectus in response to pupae infected with the fungal pathogen Metarhizium brunneum

Source data 5

Data arising from experiments showing that destructive disinfection occurs in both an additional Lasius neglectus ant supercolony and a congeneric ant species, Lasius niger, when pupae are exposed to the fungal pathogen Metarhizium brunneum or treated with a sham control

Excited-State Dynamics and Laser Action in Epitaxial Organic Nanofibers

We present a review on the excited-state dynamics and nonlinear optical properties of para-sexiphenyl epitaxial nanofibers grown on muscovite mica and exhibiting amplified spontaneous emission and random lasing at low photoexcitation fluences. We also report on recent advances made with alternated epitaxy of para-sexiphenyl and sexithiophene