116 research outputs found
Implied Calibration of Stochastic Volatility Jump Diffusion Models
In the context of arbitrage-free modelling of financial derivatives, we introduce a novel calibration technique for models in the affine- quadratic class for the purpose of contingent claims pricing and risk- management. In particular, we aim at calibrating a stochastic volatility jump diffusion model to the whole market volatility surface at any given time. We numerically implement the algorithm and show that the proposed approach is both stable and accurate.Affine-quadratic models, Option pricing, Model Calibration
Ground State Wave Function of the Schr\"odinger Equation in a Time-Periodic Potential
Using a generalized transfer matrix method we exactly solve the Schr\"odinger
equation in a time periodic potential, with discretized Euclidean space-time.
The ground state wave function propagates in space and time with an oscillating
soliton-like wave packet and the wave front is wedge shaped. In a statistical
mechanics framework our solution represents the partition sum of a directed
polymer subjected to a potential layer with alternating (attractive and
repulsive) pinning centers.Comment: 11 Pages in LaTeX. A set of 2 PostScript figures available upon
request at [email protected] . Physical Review Letter
Rational Decisions, Random Matrices and Spin Glasses
We consider the problem of rational decision making in the presence of
nonlinear constraints. By using tools borrowed from spin glass and random
matrix theory, we focus on the portfolio optimisation problem. We show that the
number of ``optimal'' solutions is generically exponentially large: rationality
is thus de facto of limited use. In addition, this problem is related to spin
glasses with L\'evy-like (long-ranged) couplings, for which we show that the
ground state is not exponentially degenerate
Correlation between generalised joint hypermobility and temporomandibular joint disc displacement in adolescent patients: Magnetic Resonance Imaging study
Aim: Temporomandibular disorders (TMD), in particular disc displacement, are recognised to have a multifactorial aetiology. Ligamentous laxity has been suggested as a potential risk factor for TMD. Ligamentous laxity can lead to generalised joint hypermobility (GJH) involving multiple joints, including the temporomandibular joint (TMJ). The aim of this work is to evaluate the correlation between GJH and disc displacement (DD) assessed on magnetic resonance images (MRI) of the TMJ in adolescent patients. Materials: The study was included 40 adolescent patients (10-16 years), divided into two groups, a Study Group (SG), composed of 20 subjects with GJH, and a Control Group (CG), composed of 20 subjects without GJH. The GJH was assessed by the Beighton test with a threshold value of ≥ 4. The severity of the TMD was determined using the Fonseca Questionnaire and a clinical evaluation of the type of TMD. The condylar-discal relationship and the condylar mobility of the TMJ were evaluated by MRI. Pearson's χ2 Test was performed for the analysis of the statistical correlation. Conclusion: This study suggests that adolescents with GJH have a greater risk of developing TMJ disc displacement, especially disc displacement without reduction
Multiple dental inclusion in monozygotic twins with congenital visual impairment
The study presents two monozygotic twins (MZ) with multiple impacted teeth, affecting the upper canines and lower second molars, as well as congenital aniridia. The clinical aspect of the upper canines is peculiar because of the different positions - palatal in one and buccal in the other twin. Studies reporting different scenarios of impaction in monozygotic twins can contribute more data to the debate on tooth eruption aetiology and more so in this case because of the association with a genetic panocular disease. Patients' Concerns. The patients were referred by a general dentist, who diagnosed the presence of multiple inclusions. Diagnostic Study. Both patients showed severe malocclusion, classified as grade 5 of the Index of Orthodontic Treatment Need (IOTN). The MZ showed class I malocclusion, upper and lower crowding, and impacted lower right and left second molars. A Dentascan was prescribed for the canine impaction. The impaction of the upper canine was palatal of 2.3 in one of the MZ and buccal of 1.3 in the other one. The same altered pattern of eruption of the lower second molars was identified in both twins. The proposed treatment plan contemplated orthodontic surgical recovery of the impacted elements, followed by orthodontic treatment with multibracket appliance after the extraction of the first four premolars, given the crowding entity. The use of a retraction spring action was chosen for the recovery of the lower second molars. Many aspects of the possible genetic aetiology of tooth impaction are still under discussion. The study of diseases in twins offers decisive information. Finally, the possibility that alterations in the eruptive pattern of the dental elements may be associated with other congenital problems broadens the range of investigations related to the possible aetiological causes of the inclusions in humans
HL-LHC layout for fixed-target experiments in ALICE based on crystal-assisted beam halo splitting
The Large Hadron Collider (LHC) at the European Organization for Nuclear
Research (CERN) is the world's largest and most powerful particle accelerator
colliding beams of protons and lead ions at energies up to 7 ZTeV, Z is the
atomic number. ALICE is one of the detector experiments optimised for heavy-ion
collisions. A fixed-target experiment in ALICE is being considered to collide a
portion of the beam halo, split using a bent crystal inserted in the transverse
hierarchy of the LHC collimation system, with an internal target placed a few
meters upstream of the existing detector. This study is carried out as a part
of the Physics Beyond Collider effort at CERN. Fixed-target collisions offer
many physics opportunities related to hadronic matter and the quark-gluon
plasma to extend the research potential of the CERN accelerator complex.
Production of physics events depends on the particle flux on target. The
machine layout for the fixed-target experiment is developed to provide a flux
of particles on the target high enough to exploit the full capabilities of the
ALICE detector acquisition system. This paper summarises the fixed-target
layout consisting of the crystal assembly, the target and downstream absorbers.
We discuss the conceptual integration of these elements within the LHC ring,
the impact on ring losses, and expected performance in terms of particle flux
on target
Efficacy and accuracy of maxillary arch expansion with clear aligner treatment
The aim of this work was to evaluate the efficacy and accuracy of maxillary arch transverse expansion using the Invisalign® clear aligner system without auxiliaries other than Invisalign attachments. Knowing the accuracy of a movement through a clear aligner system allows the clinician to plan the treatment with greater precision and to achieve the expected result faster. The study group included 28 patients with a mean age of 17 ± 3.2 years. The treatment protocol for all the selected patients included the application of the Invisalign® clear aligner system without auxiliaries, except for the Invisalign® attachments; in no case were tooth extraction or interproximal enamel reduction (IPR) performed. Linear measurements of the expansion were assessed before treatment (T0), at the end of treatment (T1), and on final virtual models by ClinCheck® (TC). A paired t-test was used to compare T0-T1 and T1-TC differences. A paired t-test was applied, and one normality was validated with the Shapiro-Wilks test. If normality was not met, the nonparametric test (Mann-Whitney U test) was applied. The level of significance was set at 5%. Statistically significant differences were found for all measurements at T0-T1. The results showed an average accuracy of efficacy of 70.88%. The differences in predictability between the various vestibular measurements (intercanine, inter-premolar, and intermolar) were not statistically significant, while they were for gingival measurements. The overall accuracy of the expansion treatment was 70%, regardless of tooth type
Mutation of aspartate 238 in FAD synthase isoform 6 increases the specific activity by weakening the FAD binding
FAD synthase (FADS, or FMN:ATP adenylyl transferase) coded by the FLAD1 gene is the last enzyme in the pathway of FAD synthesis. The mitochondrial isoform 1 and the cytosolic isoform 2 are characterized by the following two domains: the C-terminal PAPS domain (FADSy) performing FAD synthesis and pyrophosphorolysis; the N-terminal molybdopterin-binding domain (FADHy) performing a Co++ /K+-dependent FAD hydrolysis. Mutations in FLAD1 gene are responsible for riboflavin responsive and non-responsive multiple acyl-CoA dehydrogenases and combined respiratory chain deficiency. In patients harboring frameshift mutations, a shorter isoform (hFADS6) containing the sole FADSy domain is produced representing an emergency protein. With the aim to ameliorate its function we planned to obtain an engineered more efficient hFADS6. Thus, the D238A mutant, resembling the D181A FMNAT “supermutant” of C. glabrata, was overproduced and purified. Kinetic analysis of this enzyme highlighted a general increase of Km, while the kcat was two-fold higher than that of WT. The data suggest that the FAD synthesis rate can be increased. Additional modifications could be performed to further improve the synthesis of FAD. These results correlate with previous data produced in our laboratory, and point towards the following proposals (i) FAD release is the rate limiting step of the catalytic cycle and (ii) ATP and FMN binding sites are synergistically connected
Unilateral condylar hyperplasia: a thee-dimensional CBCT morphometric and volumetric evaluation of mandibular condyle by open-source softwares : Hiperplasia condilar unilateral: Evaluación morfométrica y volumétrica en TCHC tridimensional del cóndilo mandibular mediante softwares de código abierto
SUMMARY: Unilateral condylar hyperplasia (UCH) is an alteration of the mandibular condyle growth. The aim of this study was to evaluate condyle volume, surface area, and Morphological Index (MI) differences between the affected condyle and an unaffected one in patients with UCH, evaluated through 3D reconstructions cone beam computed tomography (CBCT) images by two open-source softwares. A retrospective cross-sectional study of 16 patients with a certain UCH, 9 females and 7 males with mean age 25.13 ± 6.8 years was made. The image obtained from the CBCT of each condyle were reconstructed using the open-source software 3D SLICER 4.6 ®. The volumetric and area measurements of the 3D reconstruction of the mandibular condyle were made using the open-source software NETFABB basic 5.0 ®. The mean condylar volume of the hyperplastic condyles was 2.07 ± 1.51 cm3 and the non-hyperplastic condyles was 1.16 ± 0.82 cm3 (p<0.05). The mean area surface of the hyperplastic condyle was 11.77 ± 3.71 cm2 and the non-hyperplasic condyle mean was 8.05 ± 2.17 cm2 (p < 0.05). The mean area surface difference was 3.72 ± 3.57 cm2 (28.0 %). The MI of the hyperplastic condyle was 1.8 ± 0.3 mm and the non-affected condyle was 1.3 ± 0.6 mm (p < 0.05). The use of open-source software for 3D reconstruction with manual segmentation for evaluation of the volume and the condylar surface is a valid tool available to the clinic in the diagnosis and monitoring of patients with condylar hyperplasia. © 2021, Universidad de la Frontera. All rights reserved
Study of the maxillary yaw on cone beam computed tomography: a preliminary report and comparison between two different dento‐skeletal malocclusions
Objectives: To assess the skeletal and dental maxillary transverse compensation (yaw) on the cone beam computed tomography (CBCT) three-dimensional reconstructed image of the skull in two groups of patients, both clinically affected by a class III malocclusion with deviation of the lower midline.Materials and Methods: An observational retrospective study was designed to analyse differences in two groups of patients, the first one was composed by patients affected by horizontal condylar hyperplasia, the second one by patients affected by dento-skeletal asymmetric class III malocclusion. Each group was composed by 15 patients. Transverse analysis was performed by measuring five landmarks (three bilateral and two uneven) with respect to a mid-sagittal plane; sagittal analysis was performed by measuring the sagittal distance on the mid-sagittal plane between bilateral points. Means were compared through inferential analysis.Results: In the condylar hyperplasia group, all differences between the two sides were not statistically significant, nor for canines' difference (P = .0817), for molars (P = .1105) or for jugular points (.05871). In the class III group, the differences between the two sides were statistically significant for molars (P = .0019) and jugular points (P = .0031) but not for canines (P = .1158). Comparing the two groups, significant differences were found only for incisors' midline deviation (P = .0343) and canine (P = .0177).Conclusion: The study of the yaw on CBCT should be integrated into three-dimensional cephalometry and could help in differentiating the various malocclusion patterns
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