Judicial Discretion in Corporate Bankruptcy

We study a demand and supply model of judicial discretion in corporate bankruptcy. On the supply side, we assume that bankruptcy courts may be biased for debtors or creditors, and subject to career concerns. On the demand side, we assume that debtors (and creditors) can engage in forum shopping at some cost. A key finding is that stronger creditor protection in reorganization improves judicial incentives to resolve financial distress efficiently, preventing a "race to the bottom" towards inefficient uses of judicial discretion. The comparative statics of our model shed light on a wealth of evidence on U.S. bankruptcy and yield novel predictions on how bankruptcy codes should affect firm-level outcomes.Judicial Discretion, Corporate Bankruptcy

Optimal Resolutions of Financial Distress by Contract

We study theoretically the possibility for the parties to efficiently resolve financial distress by contract as opposed to exclusively rely on state intervention. We characterize which financial contracts are optimal depending on investor protection against fraud, and how efficient is the resulting resolution of financial distress. We find that when investor protection is strong, issuing a convertible debt security to a large, secured creditor who has the exclusive right to reorganize or liquidate the firm yields the first best. Conversion of debt into equity upon default allows contracts to collateralize the whole firm to that creditor, not just certain physical assets, thereby inducing him to internalize the upside from efficient reorganization. Concentration of liquidation rights on such creditor avoids costly inter-creditor conflicts. When instead investor protection is weak, the only feasible debt structure has standard foreclosure rights, even if it induces over-liquidation. The normative implications are that lifting legal restrictions on floating charge financing, convertibles and concentration of liquidation rights, and increasing investor protection against fraud should improve the efficiency of resolutions of financial distress.Corporate Bankruptcy, Creditor Protection, Financial Contracting

Force sensing with nanowires

‘Bottom-up’ fabricated nano-resonators have emerged as particularly promising mechanical transducers, over the last decade. In fact, the exceptional force sensitivity exhibited by such nearly defect-free structures, is ensured by their small motional mass, low dissipation and high resonant frequency. In this dissertation, we aim to explore the potential of as-grown nanowires (NWs) as scanning force sensors. Their singly clamped structure makes them suitable to scan over a sample in the pendulum geometry, enabling the measurement of very weak lateral force gradients. Furthermore, by virtue of slight cross-sectional asymmetries, the flexural modes of a NW are split into doublets oscillating along two orthogonal directions. These characteristics enable the peculiar vectorial sensing nature of such devices. We developed a custom built scanning probe microscope, operating at cryogenic temperatures in a liquid helium bath cryostat. The microscope features an integrated fiber-based interferometer setup for the optical detection of individual NWs' motion. To demonstrate their vectorial scanning capabilities, we scan them over a sample with gold patterned electrodes. By monitoring the frequency shift and direction of oscillation of both fundamental modes, we construct a map of all spatial tip–sample force derivatives in the plane. Moreover, using an electric field to resonantly drive the mechanical modes, we are able to spatially probe forces of distinct origins, arising from the NW's residual charge and its polarizability, respectively. In addition, we show quantitative control over the coupling between two orthogonal mechanical modes, obtained by measuring avoided crossings as a function of position and applied electric field, which allowed to record Rabi oscillations between the two modes in the strong-coupling regime. In general, such universally applicable scanning technique enables a form of atomic force microscopy particularly suited to mapping the size and direction of weak tip-sample forces. NWs produced by molecular beam epitaxy also offer the possibility of ‘in-situ’ functionalization of the mechanical resonator during the growth process. In particular, we studied a scanning magnetic force sensor based on an individual magnet-tipped GaAs NW. Its magnetic tip consists of a final segment of single-crystal MnAs formed by sequential crystallization of the liquid Ga catalyst droplet. We characterize the mechanical and magnetic properties of such NWs by measuring their flexural mechanical response in an applied magnetic field. Taking advantage of the excellent force sensitivity, the magnetic properties of such tips are studied via dynamic torque magnetometry and precisely fitted by micro-magnetic simulations, showing vortex and dipole-like configurations. To determine a NW’s performance as a magnetic scanning probe, we measure its response to the field profile produced by a current-carrying micro-wire, characterizing its behavior as current sensor and its high sensitivity. The ability of a NW sensor to map all in-plane spatial force derivatives can provide fine detail of stray field profiles above magnetic and current carrying samples, in turn revealing information on the underlying phenomena and anisotropies. Directional measurements of dissipation may also prove useful for visualizing domain walls and other regions of inhomogeneous magnetization

Direct detection of dark matter: a critical review

The nature of the dark matter in the Universe is one of the hardest unsolved problems in modern physics. Indeed, on one hand, the overwhelming indirect evidence from astrophysics seems to leave no doubt about its existence; on the other hand, direct search experiments, especially those conducted with low background detectors in underground laboratories all over the world seem to deliver only null results, with a few debated exceptions. Furthermore, the lack of predicted candidates at the LHC energy scale has made this dichotomy even more puzzling. We will recall the most important phases of this novel branch of experimental astro-particle physics, analyzing the interconnections among the main projects involved in this challenging quest, and we will draw conclusions slightly different from how the problem is commonly understood.Comment: 28 pages, 15 picture, 2 table

Challenges for dark matter direct search with SiPMs

Liquid xenon and liquid argon detectors are leading the direct dark matter search and are expected to be the candidate technology for the forthcoming generation of ultra-sensitive large-mass detectors. At present, the scintillation light detection in those experiments is based on ultra-pure low-noise photo-multipliers. To overcome the issues in terms of the extreme radio-purity, costs, and technological feasibility of the future dark matter experiments, the novel SiPM-based photo-detector modules look promising candidates, capable of replacing the present light detection technology. However, the intrinsic features of SiPMs may limit the present expectations. In particular, interfering phenomena, especially related to the optical correlated noise, can degrade the energy and pulse shape resolutions. As a consequence, the projected sensitivity of the future detectors has to be reconsidered accordingly.Comment: 10 pages, 8 figure

A cohort study on acute ocular motility disorders in pediatric emergency department

Background: Acute ocular motility disorders (OMDs) in children admitted to Emergency Department (ED) represents a not so rare condition with a wide spectrum of different etiologies. The emergency physician must be skilled in rapidly identifying patients with potentially life threatening (LT) forms, requiring further diagnostic procedures. The aim of the study was to assess characteristics of children with acute Ocular Motility Disorders (OMDs), and to identify "red flags" for recognition of underlying life-threatening (LT) conditions. Methods: A retrospective cohort study evaluated children (2 months-17 years) admitted to a tertiary Emergency Department in 2009-2014. A subgroup analysis was performed comparing children with and without LT conditions. Results: Of 192 visits for OMDs, the isolated strabismus occurred most frequently (55.6%), followed by pupil disorders (31.8%), ptosis (5.2%) and combined OMDs (11.5%). The majority of acute OMDs involved no underlying LT conditions (n = 136) and most of them were infants or toddlers (50%). In a multivariable analysis, LT conditions included especially children over 6 years of age, increasing the odds ratio by 2% for each months of age (p = 0.009). LT etiologies were 16 times more likely in combined OMDs (p = 0.018), were over 13 times more likely to report associated extra-ocular signs/symptoms (p = 0.017) and over 50 times more likely to report co-morbidity (p = 0.017). Conclusion: OMDs are not an uncommon presentation at ED. Although most of them involve non-LT conditions, the ED physician should consider potential "red flags" for appropriate management of children such as age > 6 years, combined OMDs, extra-ocular symptoms and co-morbidity