Entrepreneurial exit in real and imagined markets

Entrepreneurs exit their business due to selection pressures experienced in the market place, i.e. business failure. Next to this well known ex-post decision to exit, entrepreneurs select exantewhether they are willing to pursue an entrepreneurial career at all, or to give up theseentrepreneurial intentions. Hardly anything is known about the latter selection process in imagined markets that precedes the variety creation and selection process in real markets. This paper explores and explains the prevalence of these two selection processes using survey data on 20,000 individuals in 27 European countries and the US in 2007. We distinguish business failures from exit by sell-off. Results indicate that individuals in the US are less likely to exit imagined markets, and are more likely to have exited the real market (especially by selling their business) than Europeans. Individuals in a Corporatist welfare state regime have relatively high chances to exit imagined markets. Business owners in urban environments are more likely to fail, while individuals with a high risk tolerance, a high education and self-employed parents are less likely to exit in imagined as well as in real markets (via business failure). This study shows that exit in real and in imagined markets is differently affected by competition and institutions. These selection environments have differential effects on entrepreneurial aspirations and actions of individuals, and provide evidence for the dissimilar nature of exit in real and exit in imagined markets.

Entrepreneurial Exit in Real and Imagined Markets

Entrepreneurs exit their business due to selection mechanisms experienced in the market place. Next to this well known ex-post decision to exit, entrepreneurs select ex-ante whether they are willing to pursue an entrepreneurial career at all, or to give up these entrepreneurial intentions. This paper compares the role of personal and ecological factors as determinants of these two types of selection: exit in real and in imagined markets. Entrepreneurs in imagined markets are more likely to exit in strong welfare state regimes, while real entrepreneurs are more likely to exit when they have low levels of human capital and when they are located in metropolitan areas

An electro-responsive hydrogel for intravascular applications: an in vitro and in vivo evaluation

There is a growing interest in using hydrogels for biomedical applications, because of more favourable characteristics. Some of these hydrogels can be activated by using particular stimuli, for example electrical fields. These stimuli can change the hydrogel shape in a predefined way. It could make them capable of adaptation to patient-specific anatomy even post-implantation. This is the first paper aiming to describe in vivo studies of an electro-responsive, Pluronic F127 based hydrogel, for intravascular applications. Pluronic methacrylic acid hydrogel (PF127/MANa) was in vitro tested for its haemolytic and cytotoxic effects. Minimal invasive implantation in the carotid artery of sheep was used to evaluate its medium-term biological effects, through biochemical, macroscopic, radiographic, and microscopic evaluation. Indirect and direct testing of the material gave no indication of the haemolytic effects of the material. Determination of fibroblast viability after 24 h of incubation in an extract of the hydrogel showed no cytotoxic effects. Occlusion was obtained within 1 h following in vivo implantation. Evaluation at time of autopsy showed a persistent occlusion with no systemic effects, no signs of embolization and mild effects on the arterial wall. An important proof-of-concept was obtained showing biocompatibility and effectiveness of a pluronic based electro-responsive hydrogel for obtaining an arterial occlusion with limited biological impact. So the selected pluronic-methacrylic acid based hydrogel can be used as an endovascular occlusion device. More importantly it is the first step in further development of electro-active hydrogels for a broad range of intra-vascular applications (e.g. system to prevent endoleakage in aortic aneurysm treatment, intra-vascular drug delivery)

A cardiovascular occlusion method based on the use of a smart hydrogel

Smart hydrogels for biomedical applications are highly researched materials. However, integrating them into a device for implantation is difficult. This paper investigates an integrated delivery device designed to deliver an electro-responsive hydrogel to a target location inside a blood vessel with the purpose of creating an occlusion. The paper describes the synthesis and characterization of a Pluronic/methacrylic acid sodium salt electro-responsive hydrogel. Application of an electrical bias decelerates the expansion of the hydrogel. An integrated delivery system was manufactured to deliver the hydrogel to the target location in the body. Ex vivo and in vivo experiments in the carotid artery of sheep were used to validate the concept. The hydrogel was able to completely occlude the blood vessel reducing the blood flow from 245 to 0 ml/min after implantation. Ex vivo experiments showed that the hydrogel was able to withstand physiological blood pressures of > 270 mm·Hg without dislodgement. The results showed that the electro-responsive hydrogel used in this paper can be used to create a long-term occlusion in a blood vessel without any apparent side effects. The delivery system developed is a promising device for the delivery of electro-responsive hydrogels

Rigidity of unilateral external fixators - A biomechanical study

Introduction: External fixation is the primary choice of temporary fracture stabilisation for specific polytrauma patients. Adequate initial fracture healing requires sufficient stability at the fracture site. The purpose of this study was to compare the rigidity of the Dynafix DFS®Standard Fixator (4 joints) with the Orthofix ProCallus Fixator®(2 joints), which differ in possibilities for adapting the configuration for clinical needs. Materials and methods: Both devices were tested 10 times in a standardised model. In steps of 10 N, loading was increased to a maximum of 160 N in parallel, transversal and axial direction (distraction and compression). Translation resultant and rotation resultant were calculated. Results: With a force of 100 N in parallel direction the mean translation resultant (Trmean) of the Dynafix DFS®Standard Fixator (6.65 ± 1.43 mm) was significantly higher than the ProCallus Fixator®(3.29 ± 0.83 mm, p < 0.001; Student's t-test). With a maximum load of 60 N in transverse direction the Trmeanof the Dynafix DFS®Standard Fixator was significantly lower (8.14 ± 1.20 mm versus 9.83 ± 0.63 mm, p < 0.005). Translation was significantly higher with the Dynafix DFS®Standard Fixator, for both distraction (2.13 ± 0.32 mm versus 1.69 ± 0.44 mm, p < 0.05) and compression (1.55 ± 1.08 mm versus 0.15 ± 0.33 mm, p < 0.005). The mean rotation resultant (Rrmean) at 160 N distraction was lower for the Dynafix DFS®Standard Fixator (0.70 ± 0.17° versus 0.97 ± 0.21°, p < 0.005). Conclusions: Both fixators were most sensitive to transverse forces. The Dynafix DFS®Standard Fixator was less rigid with parallel and axial forces, whereas transverse forces and rotation at distraction forces favoured the Dynafix DFS®Standard Fixator. Repeated heavy loading did not influence the rigidity of both devices

Regulated Membrane Localization of Tiam1, Mediated by the NH2-terminal Pleckstrin Homology Domain, Is Required for Rac-dependent Membrane Ruffling and C-Jun NH2-terminal Kinase Activation

Rho-like GTPases, including Cdc42, Rac, and Rho, regulate signaling pathways that control actin cytoskeletal structures and transcriptional activation. The Tiam1 gene encodes an activator of Rac1, and similarly to constitutively activated (V12)Rac1, overexpression of Tiam1 in fibroblasts induces the formation of membrane ruffles. Tiam1 contains a Dbl homology (DH) domain and adjacent pleckstrin homology (PH) domain, hallmarks for activators of Rho-like GTPases. Unique for Tiam1 are an additional PH domain and a Discs-large homology region in the NH2-terminal part of the protein. Here we show that both in fibroblasts and COS cells, membrane localization of Tiam1 is required for the induction of membrane ruffling. A detailed mutational analysis, in combination with confocal laser scanning microscopy and immunoelectron microscopy, demonstrates that the NH2-terminal PH domain of Tiam1, but not the DH-adjacent PH domain, is essential for membrane association. This NH2-terminal PH domain of Tiam1 can be functionally replaced by the myristoylated membrane localization domain of c-Src, indicating that the primary function of this PH domain is to localize the protein at the membrane. After serum starvation, both membrane association of Tiam1 and ruffling can be induced by serum, suggesting that receptor stimulation induces membrane translocation of Tiam1. Similar to V12Rac1, Tiam1 stimulates the activity of the c-Jun NH2-terminal kinase (JNK). This Rac-dependent stimulation of JNK also requires membrane association of Tiam1. We conclude that the regulated membrane localization of Tiam1 through its NH2-terminal PH domain determines the activation of distinct Rac-mediated signaling pathways

Topographical Organization of Mu and Beta Band Activity Associated with Hand and Foot Movements in Patients with Perirolandic Lesions

To study the topographical organization of mu and beta band event-related desynchronization (ERD) associated with voluntary hand and foot movements, we used magnetoencephalographic (MEG) recordings from 19 patients with perirolandic lesions. Synthetic aperture magnetometry (SAM) was used to detect and localize changes in the mu (7 - 11 Hz) and beta (13 - 30 Hz) frequency bands associated with repetitive movements of the hand and foot and overlaid on individual coregistered magnetic resonance (MR) images. Hand movements showed homotopic and contralateral ERD at the sensorimotor (S/M) cortex in the majority of cases for mu and to a lesser extent for beta rhythms. Foot movements showed an increased heterotopic distribution with bilateral and ipsilateral ERD compared to hand movements. No systematic topographical segregation between mu and beta ERD could be observed. In patients with perirolandic lesions, the mu and beta band spatial characteristics associated with hand movements retain the expected functional-anatomical boundaries to a large extent. Foot movements have altered patterns of mu and beta band ERD, which may give more insight into the differential functional role of oscillatory activity in different voluntary movements

Severe Radiation-Induced Lymphopenia During Concurrent Chemoradiotherapy for Stage III Non-Small Cell Lung Cancer: External Validation of Two Prediction Models

BACKGROUND: Severe radiation-induced lymphopenia (RIL) in patients undergoing chemoradiotherapy (CRT) for non-small cell lung cancer (NSCLC) is associated with decreased immunotherapy efficacy and survival. At The Christie and MD Anderson Cancer Center (MDACC), prediction models for lymphopenia were developed in lung and esophageal cancer patients, respectively. The aim of this study was to externally validate both models in patients with stage III NSCLC. METHODS: Patients who underwent concurrent CRT for stage III NSCLC in 2019-2021 were studied. Outcomes were grade ≥3 and grade 4 lymphopenia during CRT. The Christie model predictors for grade ≥3 lymphopenia included age, baseline lymphocyte count, radiotherapy duration, chemotherapy, mean heart and lung doses, and thoracic vertebrae V20Gy. MDACC predictors for grade 4 lymphopenia were age, baseline lymphocyte count, planning target volume (PTV), and BMI. The external performance of both models was assessed. RESULTS: Among 100 patients, 78 patients (78%) developed grade ≥3 lymphopenia, with grade 4 lymphopenia in 17 (17%). For predicting grade ≥3 lymphopenia, the Christie and MDACC models yielded CONCLUSION: The PTV-based MDACC prediction model for severe RIL demonstrated superior external performance in NSCLC patients compared to the dosimetry-based Christie model. As such, the MDACC model can aid in identifying patients at high risk for severe lymphopenia. However, to optimize radiotherapy planning, further improvement and external validation of dosimetry-based models is desired

Long-Term Effects of Temporal Lobe Epilepsy on Local Neural Networks: A Graph Theoretical Analysis of Corticography Recordings

Purpose: Pharmaco-resistant temporal lobe epilepsy (TLE) is often treated with surgical intervention at some point. As epilepsy surgery is considered a last resort by most physicians, a long history of epileptic seizures prior to surgery is not uncommon. Little is known about the effects of ongoing TLE on neural functioning. A better understanding of these effects might influence the moment of surgical intervention. Functional connectivity (interaction between spatially distributed brain areas) and network structure (integration and segregation of information processing) are thought to be essential for optimal brain functioning. We report on the impact of TLE duration on temporal lobe functional connectivity and network characteristics. Methods: Functional connectivity of the temporal lobe at the time of surgery was assessed by means of interictal electrocorticography (ECoG) recordings of 27 TLE patients by using the phase lag index (PLI). Graphs (abstract network representations) were reconstructed from the PLI matrix and characterized by the clustering coefficient C (local clustering), the path length L (overall network interconnectedness), and the ‘‘small world index’ ’ S (network configuration). Results: Functional connectivity (average PLI), clustering coefficients, and the small world index were negatively correlated with TLE duration in the broad frequency band (0.5–48 Hz). Discussion: Temporal lobe functional connectivity is lower in patients with longer TLE history, and longer TLE duration i