There is a growing body of evidence that many entrepreneurs seem to enter and persist in entrepreneurship despite earning low risk-adjusted returns. This has lead to attempts to provide ...explanations—using both standard economic theory and behavioral economics— for why certain individuals may be attracted to such an apparently unprofitable activity. Drawing on research in behavioral economics, in the sections that follow, we review three sets of possible interpretations for understanding the empirical facts related to the entry into, and persistence in, entrepreneurship. Differences in risk aversion provide a plausible and intuitive interpretation of entrepreneurial activity. In addition, a growing literature has begun to highlight the potential importance of overconfidence in driving entrepreneurial outcomes. Such a mechanism may appear at face value to work like a lower level of risk aversion, but there are clear conceptual differences—in particular, overconfidence likely arises from behavioral biases and misperceptions of probability distributions. Finally, nonpecuniary taste-based factors may be important in motivating both the decisions to enter into and to persist in entrepreneurship.
Human embryonic stem cells (hESCs) have two properties of interest for the development of cell therapies: self-renewal and the potential to differentiate into all major lineages of somatic cells in ...the human body. Widespread clinical application of hESC-derived cells will require culture methods that are low-cost, robust, scalable and use chemically defined raw materials. Here we describe synthetic peptide-acrylate surfaces (PAS) that support self-renewal of hESCs in chemically defined, xeno-free medium. H1 and H7 hESCs were successfully maintained on PAS for over ten passages. Cell morphology and phenotypic marker expression were similar for cells cultured on PAS or Matrigel. Cells on PAS retained normal karyotype and pluripotency and were able to differentiate to functional cardiomyocytes on PAS. Finally, PAS were scaled up to large culture-vessel formats. Synthetic, xeno-free, scalable surfaces that support the self-renewal and differentiation of hESCs will be useful for both research purposes and development of cell therapies.
Evidence on the effectiveness of highly active antiretroviral therapy (HAART) for HIV-infected individuals is limited. Most clinical trials examined surrogate endpoints over short periods of ...follow-up and there has been no placebo-controlled randomised trial of HAART. Estimation of treatment effects in observational studies is problematic, because of confounding by indication. We aimed to use novel methodology to overcome this problem in the Swiss HIV Cohort Study.
Patients were included if they had been examined after January 1996, when HAART became available in Switzerland, were not on HAART, and were free of AIDS at baseline. Cox regression models were weighted to create a statistical population in which the probability of being treated at each time point was unrelated to prognostic factors.
Low CD4 counts and increasing HIV-1 viral load were associated with increased probability of starting HAART. Overall hazard ratios were 0·14 (95% CI 0·07–0·29) for HAART compared with no treatment, and 0·49 (0·31–0·79) compared with dual therapy. Compared with no treatment, HAART became more beneficial with increasing time since initiation but was less beneficial for patients whose presumed mode of transmission was via intravenous drug use (hazard ratio 0·27, 0·12–0·61) than for other patients (0·08, 0·03–0·19).
Our results, which are appropriately controlled for confounding by indication, are consistent with reported declines in rates of AIDS and death in developed countries, and provide a context in which to consider adverse effects of HAART.
We set out to answer two questions with this study: 1. Can stroke patients improve voluntary control of their paretic ankle by practising a visuo-motor ankle-tracking task? 2. Are practice effects ...enhanced with non-invasive brain stimulation? A carefully selected sample of chronic stroke patients able to perform the experimental task attended three data collection sessions. Facilitatory transcranial direct current stimulation (tDCS) was applied in a random order over the lower limb primary motor cortex of the lesioned hemisphere or the non-lesioned hemisphere or sham stimulation was delivered over the lesioned hemisphere. In each session, tDCS was applied as patients practiced tracking a sinusoidal waveform for 15 min using dorsiflexion-plantarflexion movements of their paretic ankle. The difference in tracking error prior to, and after, the 15 min of practice was calculated. A practice effect was revealed following sham stimulation, and this effect was enhanced with tDCS applied over the lesioned hemisphere. The practice effect observed following sham stimulation was eliminated by tDCS applied over the non-lesioned hemisphere. The study provides the first evidence that non-invasive brain stimulation applied to the lesioned motor cortex of moderate- to well-recovered stroke patients enhances voluntary control of the paretic ankle. The results provide a basis for examining whether this enhanced ankle control can be induced in patients with greater impairments and whether enhanced control of a single or multiple lower limb joints improves hemiparetic gait patterns.
Significant association signals from genome-wide association studies (GWAS) point to genomic regions of interest. However, for most loci the causative genetic variant remains undefined. Determining ...expression quantitative trait loci (eQTL) in a disease relevant tissue is an excellent approach to zoom in on disease- or trait-associated association signals and hitherto on relevant disease mechanisms. To this end, we explored regulation of gene expression in healthy retina (n = 311) and generated the largest cis-eQTL data set available to date. Genotype- and RNA-Seq data underwent rigorous quality control protocols before FastQTL was applied to assess the influence of genetic markers on local (cis) gene expression. Our analysis identified 403,151 significant eQTL variants (eVariants) that regulate 3,007 genes (eGenes) (Q-Value < 0.05). A conditional analysis revealed 744 independent secondary eQTL signals for 598 of the 3,007 eGenes. Interestingly, 99,165 (24.71%) of all unique eVariants regulate the expression of more than one eGene. Filtering the dataset for eVariants regulating three or more eGenes revealed 96 potential regulatory clusters. Of these, 31 harbour 130 genes which are partially regulated by the same genetic signal. To correlate eQTL and association signals, GWAS data from twelve complex eye diseases or traits were included and resulted in identification of 80 eGenes with potential association. Remarkably, expression of 10 genes is regulated by eVariants associated with multiple eye diseases or traits. In conclusion, we generated a unique catalogue of gene expression regulation in healthy retinal tissue and applied this resource to identify potentially pleiotropic effects in highly prevalent human eye diseases. Our study provides an excellent basis to further explore mechanisms of various retinal disease etiologies.
Liquid-liquid phase separation in biology Hyman, Anthony A; Weber, Christoph A; Jülicher, Frank
Annual review of cell and developmental biology,
01/2014, Letnik:
30
Journal Article
Recenzirano
Odprti dostop
Cells organize many of their biochemical reactions in non-membrane compartments. Recent evidence has shown that many of these compartments are liquids that form by phase separation from the ...cytoplasm. Here we discuss the basic physical concepts necessary to understand the consequences of liquid-like states for biological functions.
Protists are key players in microbial communities, yet our understanding of their role in ecosystem functioning is seriously impeded by difficulties in identification of protistan species and their ...quantification. Current microscopy-based methods used for determining the abundance of protists are tedious and often show a low taxonomic resolution. Recent development of next-generation sequencing technologies offered a very powerful tool for studying the richness of protistan communities. Still, the relationship between abundance of species and number of sequences remains subjected to various technical and biological biases. Here, we test the impact of some of these biological biases on sequence abundance of SSU rRNA gene in foraminifera. First, we quantified the rDNA copy number and rRNA expression level of three species of foraminifera by qPCR. Then, we prepared five mock communities with these species, two in equal proportions and three with one species ten times more abundant. The libraries of rDNA and cDNA of the mock communities were constructed, Sanger sequenced and the sequence abundance was calculated. The initial species proportions were compared to the raw sequence proportions as well as to the sequence abundance normalized by rDNA copy number and rRNA expression level per species. Our results showed that without normalization, all sequence data differed significantly from the initial proportions. After normalization, the congruence between the number of sequences and number of specimens was much better. We conclude that without normalization, species abundance determination based on sequence data was not possible because of the effect of biological biases. Nevertheless, by taking into account the variation of rDNA copy number and rRNA expression level we were able to infer species abundance, suggesting that our approach can be successful in controlled conditions.
1Kor 2,12–16 28.5.2023 Pfingstsonntag Weber, Christel E. A.
Pastoraltheologie : Monatsschrift für Wissenschaft und Praxis in Kirche und Gesellschaft,
01/2023, Letnik:
112, Številka:
2
Journal Article
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