Over the past three decades, significant research efforts have focused on improving the charge carrier mobility of organic thin‐film transistors (OTFTs). In recent years, a commonly observed ...nonlinearity in OTFT current–voltage characteristics, known as the “kink” or “double slope,” has led to widespread mobility overestimations, contaminating the relevant literature. Here, published data from the past 30 years is reviewed to uncover the extent of the field‐effect mobility hype and identify the progress that has actually been achieved in the field of OTFTs. Present carrier‐mobility‐related challenges are identified, finding that reliable hole and electron mobility values of 20 and 10 cm2 V−1 s−1, respectively, have yet to be achieved. Based on the analysis, the literature is then reviewed to summarize the concepts behind the success of high‐performance p‐type polymers, along with the latest understanding of the design criteria that will enable further mobility enhancement in n‐type polymers and small molecules, and the reasons why high carrier mobility values have been consistently produced from small molecule/polymer blend semiconductors. Overall, this review brings together important information that aids reliable OTFT data analysis, while providing guidelines for the development of next‐generation organic semiconductors.
Overestimated carrier mobility values reported in recent years for organic thin‐film transistors (OTFTs) have contaminated the literature. 30 years of OTFT carrier mobility data is examined in an effort to identify actual progress achieved, and summarize the key design strategies behind high carrier mobility values for both p‐ and n‐type organic semiconductors.
The structure and dynamics of the water/vapor interface is revisited by means of path-integral and second-generation Car–Parrinello ab initio molecular dynamics simulations in conjunction with an ...instantaneous surface definition Willard, A. P.; Chandler, D. J. Phys. Chem. B 2010, 114, 1954. In agreement with previous studies, we find that one of the OH bonds of the water molecules in the topmost layer is pointing out of the water into the vapor phase, while the orientation of the underlying layer is reversed. Therebetween, an additional water layer is detected, where the molecules are aligned parallel to the instantaneous water surface.
xion miniclusters are dense bound structures of dark matter axions that are predicted to form in the postinflationary Peccei-Quinn symmetry breaking scenario. Although dense, miniclusters can easily ...be perturbed or even become unbound by interactions with baryonic objects such as stars. Here, we characterize the spatial distribution and properties of miniclusters in the Milky Way (MW) today after undergoing these stellar interactions throughout their lifetime. We do this by performing a suite of Monte Carlo simulations which track the miniclusters' structure and, in particular, accounts for partial disruption and mass loss through successive interactions. We consider two density profiles-Navarro-Frenk-White (NFW) and power-law (PL)-for the individual miniclusters in order to bracket the uncertainties on the minicluster population today due to their uncertain formation history. For our fiducial analysis at the solar position, we find a survival probability of 99% for miniclusters with PL profiles and 46% for those with NFW profiles. Our work extends previous estimates of this local survival probability to the entire MW. We find that towards the Galactic Center, the survival probabilities drop drastically. Although we present results for a particular initial halo mass function, our simulations can be easily recast to different models using the provided data and code (github.com/bradkav/axion-miniclusters). Finally, we comment on the impact of our results on lensing, direct, and indirect detection.
The discovery of rubisco Sharkey, Thomas D
Journal of experimental botany,
01/2023, Volume:
74, Issue:
2
Journal Article
Peer reviewed
Rubisco is possibly the most important enzyme on Earth, certainly in terms of amount. This review describes the initial reports of ribulose 1,5-bisphosphate carboxylating activity. Discoveries of ...core concepts are described, including its quaternary structure, the requirement for post-translational modification, and its role as an oxygenase as well as a carboxylase. Finally, the requirement for numerous chaperonins for assembly of rubisco in plants is described.
Ecosystems—communities of interdependent yet hierarchically independent heterogeneous participants who collectively generate an ecosystem value proposition—often emerge through collective action, ...where ecosystem participants interact with each other and the external environment. When such organizational forms are emerging, they require legitimacy to overcome the “liability of newness.” Adopting a collective action lens and taking a legitimacy-as-process approach, we propose a process model of ecosystem collective action, where an orchestrator, complementors, users, and external actors together drive ecosystem legitimacy. We identify three key legitimation processes—discursive legitimation, performative legitimation, and ecosystem identity construction—and demonstrate how these three processes together facilitate the emergence of ecosystem legitimacy and reduce the liability of newness of emerging ecosystems.
The sensory cortex contains a wide array of neuronal types, which are connected together into complex but partially stereotyped circuits. Sensory stimuli trigger cascades of electrical activity ...through these circuits, causing specific features of sensory scenes to be encoded in the firing patterns of cortical populations. Recent research is beginning to reveal how the connectivity of individual neurons relates to the sensory features they encode, how differences in the connectivity patterns of different cortical cell classes enable them to encode information using different strategies, and how feedback connections from higher-order cortex allow sensory information to be integrated with behavioural context.
Haplodeficiency of the microglia gene TREM2 increases risk for late-onset Alzheimer’s disease (AD) but the mechanisms remain uncertain. To investigate this, we used high-resolution confocal and ...super-resolution (STORM) microscopy in AD-like mice and human AD tissue. We found that microglia processes, rich in TREM2, tightly surround early amyloid fibrils and plaques promoting their compaction and insulation. In Trem2- or DAP12-haplodeficient mice and in humans with R47H TREM2 mutations, microglia had a markedly reduced ability to envelop amyloid deposits. This led to an increase in less compact plaques with longer and branched amyloid fibrils resulting in greater surface exposure to adjacent neurites. This was associated with more severe neuritic tau hyperphosphorylation and axonal dystrophy around amyloid deposits. Thus, TREM2 deficiency may disrupt the formation of a neuroprotective microglia barrier that regulates amyloid compaction and insulation. Pharmacological modulation of this barrier could be a novel therapeutic strategy for AD.
•TREM2/DAP12 signaling regulates microglia process envelopment of amyloid plaques•Loss of microglia envelopment in TREM2/DAP12 deficiency reduces plaque compaction•STORM microscopy shows greater fibril branching and surface area in TREM2 deficiency•Human R47H TREM2 variant impairs the microglia barrier and worsens axonal dystrophy
Yuan, Condello, et al. demonstrate that haplodeficiency of the microglia-specific gene TREM2 markedly impairs the ability of microglia to compact and insulate amyloid deposits. Loss of this neuroprotective microglia function leads to marked axonal dystrophy, potentially contributing to the increased risk of dementia for carriers of TREM2 loss-of-function mutations.
PANTHER-PSEP is a new software tool for predicting non-synonymous genetic variants that may play a causal role in human disease. Several previous variant pathogenicity prediction methods have been ...proposed that quantify evolutionary conservation among homologous proteins from different organisms. PANTHER-PSEP employs a related but distinct metric based on 'evolutionary preservation': homologous proteins are used to reconstruct the likely sequences of ancestral proteins at nodes in a phylogenetic tree, and the history of each amino acid can be traced back in time from its current state to estimate how long that state has been preserved in its ancestors. Here, we describe the PSEP tool, and assess its performance on standard benchmarks for distinguishing disease-associated from neutral variation in humans. On these benchmarks, PSEP outperforms not only previous tools that utilize evolutionary conservation, but also several highly used tools that include multiple other sources of information as well. For predicting pathogenic human variants, the trace back of course starts with a human 'reference' protein sequence, but the PSEP tool can also be applied to predicting deleterious or pathogenic variants in reference proteins from any of the ∼100 other species in the PANTHER database.
PANTHER-PSEP is freely available on the web at http://pantherdb.org/tools/csnpScoreForm.jsp Users can also download the command-line based tool at ftp://ftp.pantherdb.org/cSNP_analysis/PSEP/ CONTACT: pdthomas@usc.edu
Supplementary data are available at Bioinformatics online.
We determined how learning modifies neural representations in primary visual cortex (V1) during acquisition of a visually guided behavioral task. We imaged the activity of the same layer 2/3 neuronal ...populations as mice learned to discriminate two visual patterns while running through a virtual corridor, where one pattern was rewarded. Improvements in behavioral performance were closely associated with increasingly distinguishable population-level representations of task-relevant stimuli, as a result of stabilization of existing and recruitment of new neurons selective for these stimuli. These effects correlated with the appearance of multiple task-dependent signals during learning: those that increased neuronal selectivity across the population when expert animals engaged in the task, and those reflecting anticipation or behavioral choices specifically in neuronal subsets preferring the rewarded stimulus. Therefore, learning engages diverse mechanisms that modify sensory and non-sensory representations in V1 to adjust its processing to task requirements and the behavioral relevance of visual stimuli.
•V1 neurons increasingly discriminate task-relevant stimuli with learning•Chronic imaging reveals single cell changes underlying this population effect•Learning-related changes are reduced when animals ignore task-relevant stimuli•Anticipatory and behavioral choice-related signals emerge in reward-predicting cells
By tracking the same visual cortex neurons across days, Poort et al. demonstrate how learning a visual task leads to increasingly distinguishable representations of relevant stimuli. These changes parallel the emergence of diverse non-sensory signals in specific neuronal subsets.
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