Essays on Angel Investing in the Entrepreneurial Ecosystem

Throughout its three chapters, this dissertation examines a phenomenon that, although underappreciated and underinvestigated in the existing literature, should be of great interest to entrepreneurship scholars: angel investing in the United States. While most of the existing studies of venture financing have predominantly focused on venture capital (VC) funding, angel investing—that is, wealthy individuals investing their own money in new ventures—represents almost as large of a market as venture capital, and recent empirical evidence suggests that ventures financed by angel investors tend to be more successful than comparable ventures that are not angel-financed. More interestingly, perhaps, angel investing tends to focus on ventures at the earliest stage, which leads to investor making decisions based on very little hard evidence. This results in the attempt, on the investors’ part, to reduce uncertainty by leveraging one’s connections and community-level patterns of social relations. In this regard, this dissertation’s main objective is perhaps to tackle the existing literature’s “undersocialized” take on venture financing, and to show the sociological mechanisms that might underpin the decision by entrepreneurs to enter the angel investing market by becoming suppliers of capital, as well as their capital allocation choices, i.e. their investment decisions. Additionally, this work also examines the drivers of success for angel investors, with a view to explaining—at least in part—why certain individuals are wildly more successful than others at angel investing. Empirically, my work relies on a combination of archival data—primarily data gathered from online data source CrunchBase, but also U.S. Census data and hand-collected information from LinkedIn—and fieldwork in the form of interviews with entrepreneurs and angel investors, as well as participant observation at the Angel Capital Association Annual Meeting in San Francisco, the largest yearly gathering of angel investors. The resulting empirical patterns, both qualitative and quantitative, when taken in their entirety suggests that angel investing is a social process, and particularly that entrepreneurs are socialized into becoming angel investors by interacting with the angels who finance their ventures. Further, this work offers evidence that community-level patterns of socialization—i.e. what is generally known in sociology as community social capital—also plays a role in determining whether entrepreneurs will become angel investors and, once they choose to take this step, whether they will show a preference for financing local ventures vis-à-vis pursuing investment opportunities elsewhere. Finally, this work also addresses the question of angel investing outcomes—that is, why some angel investors are more successful than others, as measured by the number of exits in their investment portfolio. In this regard, empirical results suggest that generalists do better than specialists, and that angel investors with broad entrepreneurial experience are found to do especially well. Success is also a function of effective knowledge translation: on average, successful entrepreneurs tend to become more successful angels, and especially so the greater the overlap between the entrepreneurial experience of the founder and their angel investment portfolio

Discrete Breathers in a Realistic Coarse-Grained Model of Proteins

We report the results of molecular dynamics simulations of an off-lattice protein model featuring a physical force-field and amino-acid sequence. We show that localized modes of nonlinear origin (discrete breathers) emerge naturally as continuations of a subset of high-frequency normal modes residing at specific sites dictated by the native fold. In the case of the small $\beta$-barrel structure that we consider, localization occurs on the turns connecting the strands. At high energies, discrete breathers stabilize the structure by concentrating energy on few sites, while their collapse marks the onset of large-amplitude fluctuations of the protein. Furthermore, we show how breathers develop as energy-accumulating centres following perturbations even at distant locations, thus mediating efficient and irreversible energy transfers. Remarkably, due to the presence of angular potentials, the breather induces a local static distortion of the native fold. Altogether, the combination of this two nonlinear effects may provide a ready means for remotely controlling local conformational changes in proteins.Comment: Submitted to Physical Biolog

GEN-IV LFR development: Status & perspectives

Since Lead-cooled Fast Reactors (LFR) have been conceptualized in the frame of Generation IV International Forum (GIF), great interest has focused on the development and testing of new technologies related to Heavy Liquid Metal (HLM) nuclear reactors. In this frame, ENEA developed one of the larger European experimental fleet of experimental facilities aiming at investigating HLM thermal-hydraulics, coolant chemistry control, corrosion behavior for structural materials, and at developing components, instrumentations and innovative systems, supported by experiments and numerical tools. The present work aims at highlighting the capabilities and competencies developed by ENEA so far in the frame of the liquid metal technologies for GEN-IV LFR. In particular, an overview on the ongoing R&D experimental program will be depicted considering the actual fleet of facilities: CIRCE, NACIE-UP, LIFUS5, LECOR and HELENA. CIRCE (CIRColazione Eutettico) is the largest HLM pool facility presently in operation worldwide. Full scale component tests, thermal stratification studies, operational and accidental transients and integral tests for the nuclear safety and SGTR (Steam Generator Tube Rupture) events in a large pool system can be studied. NACIE-UP (NAtural CIrculation Experiment-UPgraded) is a loop with a HLM primary and pressurized water secondary side and a 250 kW power Fuel Pin Simulator working in natural and mixed convection. LIFUS5 (lithium for fusion) is a separated effect facility devoted to the HLM/Water interaction. HELENA (HEavy Liquid metal Experimental loop for advanced Nuclear applications) is a pure lead loop with a mechanical pump for high flow rates experiments. LECOR (LEad CORrosion) is a corrosion loop facility with oxygen control system installed. All the experiment actually ongoing on these facilities are described in the paper, depicting their role in the context of GEN-IV LFR development

Structured Light Plethysmography (SLP): Management and follow up of a paediatric patient with pneumonia

Structured Light Plethysmography (SLP) is a non-invasive method to study chest and abdominal movement during breathing and can identify abnormal contributions of the different regions of the chest. M.D hospitalized for pneumonia, underwent SLP and spirometry at admission (T0), after 48 hours (T1), and after one month (T2). SLP parameters showed expiratory flow limitation, information consistent with the spirometric parameters collected, and reduced motion in the area effected by pneumonia, with improvement and normalization at T1 and T2. This method gave useful information about the contribution to the respiratory movement of the lung area affected by pneumonia so we can speculate a possible use in the follow-up of children affected by pneumonia or other respiratory diseases, and who are not able to perform a spirometric test

Adaptive Synergies for the Design and Control of the Pisa/IIT SoftHand

In this paper we introduce the Pisa/IIT SoftHand, a novel robot hand prototype designed with the purpose of being robust and easy to control as an industrial gripper, while exhibiting high grasping versatility and an aspect similar to that of the human hand. In the paper we briefly review the main theoretical tools used to enable such simplification, i.e. the neuroscience-based notion of soft synergies. A discussion of several possible actuation schemes shows that a straightforward implementation of the soft synergy idea in an effective design is not trivial. The approach proposed in this paper, called adaptive synergy, rests on ideas coming from underactuated hand design. A synthesis method to realize a desired set of soft synergies through the principled design of adaptive synergy is discussed. This approach leads to the design of hands accommodating in principle an arbitrary number of soft synergies, as demonstrated in grasping and manipulation simulations and experiments with a prototype. As a particular instance of application of the synthesis method of adaptive synergies, the Pisa/IIT SoftHand is described in detail. The hand has 19 joints, but only uses 1 actuator to activate its adaptive synergy. Of particular relevance in its design is the very soft and safe, yet powerful and extremely robust structure, obtained through the use of innovative articulations and ligaments replacing conventional joint design. The design and implementation of the prototype hand are shown and its effectiveness demonstrated through grasping experiments, reported also in multimedia extensio

Stand-alone oblique lumbar interbody fusion (OLIF) for the treatment of adjacent segment disease (ASD) after previous posterior lumbar fusion: clinical and radiological outcomes and comparison with posterior revision surgery

Background: Radiological evidence of adjacent segment disease (ASD) has been reported to have a prevalence of more than 30% and several risk factors have been reported. The aim of this study is to evaluate the clinical and radiological outcomes of patients with symptomatic ASD treated with stand-alone OLIF and compare results with a posterior revision surgery cohort. Methods: This is a retrospective case-control study. Clinical-patient-reported outcomes were obtained at preoperative, postoperative and final follow-up visits using the Short Form (SF-36) scale, the Oswestry Disability Index (ODI) and the visual analog scale (VAS). Radiological measures include lumbar lordosis (LL), segmental lordosis (SL), pelvic incidence-lumbar lordosis (PI-LL) mismatch, segmental coronal Cobb angle and intervertebral disc height (DH). The data are compared with a retrospective series of patients that underwent a posterior revision surgery for ASD. Results: Twenty-eight patients in the OLIF group and 25 patients in the posterior group meet inclusion criteria. The mean ages at the time of the surgery are 65.1 years and 67.5, respectively. The mean follow-up time is 36.1 months (range of 14-56). The clinical outcomes significantly improve from preoperative values from the surgery in both groups. The radiological parameters are significantly improved postoperatively and were maintained at the last follow-up in both groups. A statistically significant difference is observed between the two groups for minor complication rate, length of surgery, blood loss and DH restoration. Conclusions: Stand-alone OLIF is an effective and safe technique with low morbidity and complication rates for the treatment of selected patients with symptomatic ASD following a previous lumbar fusion

Airways flat angioma misdiagnosed as difficult asthma in an adolescent

A 15 years-old boy came to our attention with a diagnosis of poorly controlled asthma. This case required thorough investigations: CT scan imaging revealed a flat angioma extending from the carina to the left main bronchus. Rigid bronchoscopy confirmed the presence of an angioma showing widespread mucosal diffusion involving most of the posterior tracheal wall and main bronchi, on the left side. We present this case report and these images to readers seeking for other experiences in the diagnosis of wide superficial bronchial angioma in pediatric age

Real-Time Laryngeal Cancer Boundaries Delineation on White Light and Narrow-Band Imaging Laryngoscopy with Deep Learning

Objective: To investigate the potential of deep learning for automatically delineating (segmenting) laryngeal cancer superficial extent on endoscopic images and videos. Methods: A retrospective study was conducted extracting and annotating white light (WL) and Narrow-Band Imaging (NBI) frames to train a segmentation model (SegMENT-Plus). Two external datasets were used for validation. The model's performances were compared with those of two otolaryngology residents. In addition, the model was tested on real intraoperative laryngoscopy videos. Results: A total of 3933 images of laryngeal cancer from 557 patients were used. The model achieved the following median values (interquartile range): Dice Similarity Coefficient (DSC) = 0.83 (0.70-0.90), Intersection over Union (IoU) = 0.83 (0.73-0.90), Accuracy = 0.97 (0.95-0.99), Inference Speed = 25.6 (25.1-26.1) frames per second. The external testing cohorts comprised 156 and 200 images. SegMENT-Plus performed similarly on all three datasets for DSC (p = 0.05) and IoU (p = 0.07). No significant differences were noticed when separately analyzing WL and NBI test images on DSC (p = 0.06) and IoU (p = 0.78) and when analyzing the model versus the two residents on DSC (p = 0.06) and IoU (Senior vs. SegMENT-Plus, p = 0.13; Junior vs. SegMENT-Plus, p = 1.00). The model was then tested on real intraoperative laryngoscopy videos. Conclusion: SegMENT-Plus can accurately delineate laryngeal cancer boundaries in endoscopic images, with performances equal to those of two otolaryngology residents. The results on the two external datasets demonstrate excellent generalization capabilities. The computation speed of the model allowed its application on videolaryngoscopies simulating real-time use. Clinical trials are needed to evaluate the role of this technology in surgical practice and resection margin improvement. Level of evidence: III Laryngoscope, 2024