Extreme Value Theory and Auction Models

The objective of this article is to develop a parametric approach to estimating auctions with incomplete data using Extreme Value Theory (EVT).  The methodology is mainly theoretical: we first review that, when only transaction prices can be observed, the distribution of private valuations is irregularly identified. The sample bias produced by nonparametric estimators will affect all functionals of practical interest.  We provide simulations for a best-case scenario and a worst-case scenario.  Our results show that, compared to nonparametric approaches, the approximation of such functionals developed using EVT produces more accurate results, is easy to compute, and does not require strong assumptions about the unobserved distribution of bidders' valuations.  It is recommended that financial operators working with auctions use this parametric approach when facing incomplete datasets.  Given the difficult nature of the analysis, this work does not provide large sample properties for the proposed estimators and recommends the use of bootstrapping.  This article contributes originally to the literature of structural estimation of auction models providing a useful and robust parametric approximation.Teoría de valores extremos y modelos de subastas El objetivo de este artículo es desarrollar un enfoque paramétrico para estimar subastas con datos incompletos utilizando la Teoría de los Valores Extremos (EVT). La metodología es principalmente teórica: primero revisamos que, cuando solo se pueden observar los precios de transacción, la distribución de las valoraciones privadas se identifica de manera irregular. El sesgo de la muestra producido por los estimadores no paramétricos afectará a todos las formas funcionales de interés práctico. Proporcionamos simulaciones para el mejor de los casos y el peor de los casos. Nuestros resultados muestran que, en comparación con los enfoques no paramétricos, la aproximación de tales formas funcionales desarrolladas usando EVT produce resultados más precisos, es fácil de calcular y no requiere fuertes suposiciones sobre la distribución no observada de las valoraciones de los oferentes. Se recomienda que los operadores financieros que trabajan con subastas utilicen este enfoque paramétrico cuando se enfrentan a conjuntos de datos incompletos. Dada la naturaleza difícil del análisis, este trabajo no proporciona propiedades de muestra grande para los estimadores propuestos y recomienda el uso de bootstrapping. Este artículo contribuye originalmente a la literatura de estimación estructural de modelos de subasta proporcionando una aproximación paramétrica útil y robusta

A retrospective cephalometric study on pharyngeal airway space changes after rapid palatal expansion and herbst appliance with or without skeletal anchorage

Background: The aim of this study is to investigate the pharyngeal airway space changes in patients treated with rapid palatal expansion (RPE) and Herbst appliance with or without skeletal anchorage. Methods: A 40-patient study group treated with the Herbst RME combination was included; moreover, a comparison between two subgroups based on whether miniscrews were used was evaluated. A subgroup 1 included 20 patients who were treated with RPE and an acrylic splint Herbst with miniscrews, and subgroup 2 included 20 patients who were treated with RPE and an acrylic splint Herbst. A cephalometric analysis was performed before (T1) and after (T2) treatment. The skeletal parameters of the sagittal occlusion analysis of Pancherz were utilized together with some extra measurements to evaluate the airways. Results: An increased nasopharyngeal airway space was observed in group 1 (p < 0.05) from T1 to T2. Furthermore, the increase in nasopharyngeal airway space was significantly higher in subgroup 1 (p < 0.05) in comparison to the subgroup 2. Oropharyngeal (OA) and laryngopharyngeal (LA) dimensions were significantly increased in the subgroup 1 at the end of the treatment. In the subgroup 1, a significant decrease in SNA, a significant increase in SNB, and a significant decrease in ANB were observed from T1 to T2. In the subgroup 2, the treatment resulted in a significant decrease in ANB. In both groups, Pogonion increased significantly from T1 to T2. Conclusions: The results suggest that the RPE and the Herbst appliance allow a slight improvement of the sagittal dimensions of the airways. The oropharyngeal dimension increased significantly more in the skeletal anchorage group

Intraoperative β-Detecting probe for radio-guided surgery in tumour resection

The development of the β− based radio-guided surgery aims to extend the technique to those tumours where surgery is the only possible treatment and the assessment of the resection would most profit from the low background around the lesion, as for brain tumours. Feasibility studies on meningioma and gliomas already estimated the potentiality of this new treatment. To validate the technique, a prototype of the intraoperative probe detecting β− decays and specific phantoms simulating tumour remnant patterns embedded in healthy tissue have been realized. The response of the probe in this simulated environment is tested with dedicated procedures. This document discusses the innovative aspects of the method, the status of the developed intraoperative β− detecting probe and the results of the preclinical tests

Sternal Wound Complications: Results of Routine Use of Negative Pressure Wound Therapy

Introduction: Negative pressure wound therapy (NPWT) has significantly improved outcomes in individuals with superficial and deep sternal wound dehiscence (SWD). We report our experience with NPWT to evaluate factors influencing effectiveness, duration of treatment and postoperative hospital stay. Methods: We reviewed 92 patients with postoperative SWD following a median sternotomy. Patients were divided into 2 groups: those with a superficial SWD (Group 1; 72, 78%) and those with a deep SWD (Group 2; 20, 28%). Group 1 was further divided into 3 subgroups based on NPWT duration. Results: In both groups, none of the preoperative characteristics examined showed a significant association with longer NPWT duration. In Group 2, there was a trend for postoperative bleeding and neurological complications to be associated with longer DOI: 10.21470/1678-9741-2019-0242 treatment duration. In the entire series, staph infection resulted a weak predictor of NPWT duration. In each Group 1 subgroup and in Group 2, treatment days were compared with duration of hospitalization until discharge. Mean post-NPWT hospital stay was 6 days in subgroup 1, 12 days in subgroup 2 and 20 days in subgroup 3 (P<0.0001). At a median 3-year follow-up, there were 4 late deaths, none related to wound complications. No cases of SWD recurrence were observed. Conclusions: Our results confirm the effectiveness of NPWT in SWD management, while excessive treatment duration might have a negative impact on the length of hospital stay. Further studies are needed to define an optimal use of NPWT protocol

An Intraoperative β−\beta^- Detecting Probe For Radio-Guided Surgery in Tumour Resection

The development of the $\beta^-$ based radio-guided surgery aims to extend the technique to those tumours where surgery is the only possible treatment and the assessment of the resection would most profit from the low background around the lesion, as for brain tumours. Feasibility studies on meningioma, glioma, and neuroendocrine tumors already estimated the potentiality of this new treatment. To validate the technique, prototypes of the intraoperative probe required by the technique to detect $\beta^-$ radiation have been developed. This paper discusses the design details of the device and the tests performed in laboratory. In such tests particular care has to be taken to reproduce the surgical field conditions. The innovative technique to produce specific phantoms and the dedicated testing protocols is described in detail.Comment: 7 pages, 15 figure

16 years follow-up evaluation of immediate vs delayed vs. combined hormonal therapy on fertility of patients with cryptorchidism: results of a longitudinal cohort study

To investigate in a longitudinal cohort study, the best treatment to preserve fertility in cryptorchid subjects. Patients treated with immediate hormonal vs. delayed vs. combined (hormone plus surgery) therapy consecutively enrolled during the period 1987-1997, were evaluated

Fetal oxygenation in the last weeks of pregnancy evaluated through the umbilical cord blood gas analysis

IntroductionEmbryo and fetus grow and mature over the first trimester of pregnancy in a dynamic hypoxic environment, where placenta development assures an increased oxygen availability. However, it is unclear whether and how oxygenation changes in the later trimesters and, more specifically, in the last weeks of pregnancy.MethodsObservational study that evaluated the gas analysis of the umbilical cord blood collected from a cohort of healthy newborns with gestational age >= 37 weeks. Umbilical venous and arterial oxygen levels as well as fetal oxygen extraction were calculated to establish whether oxygenation level changes over the last weeks of pregnancy. In addition, fetal lactate, and carbon dioxide production were analyzed to establish whether oxygen oscillations may induce metabolic effects in utero.ResultsThis study demonstrates a progressive increase in fetal oxygenation levels from the 37th to the 41st weeks of gestation (mean venous PaO2 approximately from 20 to 25 mmHg; p < 0.001). This increase is largely attributable to growing umbilical venous PaO2, regardless of delivery modalities. In neonates born by vaginal delivery, the increased oxygen availability is associated with a modest increase in oxygen extraction, while in neonates born by cesarean section, it is associated with reduced lactate production. Independently from the type of delivery, carbon dioxide production moderately increased. These findings suggest a progressive shift from a prevalent anaerobic metabolism (Warburg effect) towards a growing aerobic metabolism.ConclusionThis study confirms that fetuses grow in a hypoxic environment that becomes progressively less hypoxic in the last weeks of gestation. The increased oxygen availability seems to favor aerobic metabolic shift during the last weeks of intrauterine life; we hypothesize that this environmental change may have implications for fetal maturation during intrauterine life

Monitoring of hadrontherapy treatments by means of charged particle detection

The interaction of the incoming beam radiation with the patient body in hadrontherapy treatments produces secondary charged and neutral particles, whose detection can be used for monitoring purposes and to perform an on-line check of beam particle range. In the context of ion-therapy with active scanning, charged particles are potentially attractive since they can be easily tracked with a high efficiency, in presence of a relatively low background contamination. In order to verify the possibility of exploiting this approach for in-beam monitoring in ion-therapy, and to guide the design of specific detectors, both simulations and experimental tests are being performed with ion beams impinging on simple homogeneous tissue-like targets (PMMA). From these studies, a resolution of the order of few millimeters on the single track has been proven to be sufficient to exploit charged particle tracking for monitoring purposes, preserving the precision achievable on longitudinal shape. The results obtained so far show that the measurement of charged particles can be successfully implemented in a technology capable of monitoring both the dose profile and the position of the Bragg peak inside the target and finally lead to the design of a novel profile detector. Crucial aspects to be considered are the detector positioning, to be optimized in order to maximize the available statistics, and the capability of accounting for the multiple scattering interactions undergone by the charged fragments along their exit path from the patient body. The experimental results collected up to now are also valuable for the validation of Monte Carlo simulation software tools and their implementation in Treatment Planning Software packages

A single-operator experience using EchoLaser SoracteLiteTM for focal laser ablation of prostate cancer: One more arrow in the quiver for the conservative management of the disease

Background: The aim of this study was to evaluate the outcomes of patients suffering prostate cancer (PCa) treated conservatively using 1064 nm laser energy for focal laser ablation (FLA). The patients included in the study were unsuitable for surgery or unwilling to receive external beam radiotherapy because they were afraid of the possible side effects of whole-gland therapies. Methods: This study included patients with a diagnosis of nonmetastatic PCa who underwent FLA using SoracteLiteTM system. Tissue ablation was performed at a fixed power of 5 W by the diode multichannel laser system EchoLaser X4 that uses laser light transmitted through optical fibres causing the target tissue to undergo irreversible thermal damage. Functional outcomes were evaluated with the International Prostatic Symptoms Score (IPSS) and 5-item version of the International Index of Erectile Function (IIEF-5) before the treatment and one year later. Results: Ten patients suffering non-metastatic PCa were included. Four decided upon a conservative treatment because of reduced performance status and for six patients the procedure was chosen electively. All patients underwent multiparametric magnetic resonance imaging at 3 and 12 months and eight out of ten patients underwent prostate biopsy at 6 months. Persistent disease was detected in 3 patients who underwent a second ablation. In these patients at the biopsy following the second ablation none harbored residual disease. At follow-up, no patient suffered urinary incontinence requiring the use of pads. No significant worsening in sexual potency measured with IIEF-5 (p = 0.356) or prostatic symptoms measured at IPSS (p = 0.462) were recorded comparing pre-treatment condition vs one-year follow-up. Compared with baseline, prostate-specific antigen was significantly reduced at one-year follow-up (3.7 ± 1.1 vs 7.9 ± 4.1 ng/mL; p = 0.008). Conclusions: Although whole gland therapies remain the gold standard treatment for PCa, our results indicate that the SoracteLiteTM system for focal laser ablation, as a very preliminary step, appears to offer a short-term oncologic control of PCa with negligible side effects

'Incidental' and 'non-incidental' thyroid papillary microcarcinomas are two different entities

Papillary thyroid microcarcinomas (microPTC) may be 'incidental' (Inc-microPTC), occasionally found at histology after surgery for benign disease or 'non-incidental' (Non-Inc-microPTC), diagnosed on clinical grounds. It is unclear whether these different microPTC reflect the same disease. The aim of the study was to compare Inc-microPTC and Non-Inc-microPTC for clinical and histological features as well as for serum TSH, a known factor involved in PTC development