Uncertainty quantification in timber-like beams using sparse grids: theory and examples with off-the-shelf software utilization

When dealing with timber structures, the characteristic strength and stiffness of the material are made highly variable and uncertain by the unavoidable, yet hardly predictable, presence of knots and other defects. In this work we apply the sparse grids stochastic collocation method to perform uncertainty quantification for structural engineering in the scenario described above. Sparse grids have been developed by the mathematical community in the last decades and their theoretical background has been rigorously and extensively studied. The document proposes a brief practice-oriented introduction with minimal theoretical background, provides detailed instructions for the use of the already implemented Sparse Grid Matlab kit (freely available on-line) and discusses two numerical examples inspired from timber engineering problems that highlight how sparse grids exhibit superior performances compared to the plain Monte Carlo method. The Sparse Grid Matlab kit requires only a few lines of code to be interfaced with any numerical solver for mechanical problems (in this work we used an isogeometric collocation method) and provides outputs that can be easily interpreted and used in the engineering practice

Non-prismatic Timoshenko-like beam model

The present paper combines an effective beam theory with a simple and accurate numerical technique opening the door to the prediction of the structural behavior of planar beams characterized by a continuous variation of the cross-section geometry, that in general deeply influences the stress distribution and, therefore, leads to non-trivial constitutive relations. Accounting for these peculiar aspects, the beam theory is described by a mixed formulation of the problem represented by six linear Ordinary Differential Equations (ODEs) with non-constant coefficients depending on both the cross-section displacements and the internal forces. Due to the ODEs complexity, the solution can be typically computed only numerically also for relatively simple geometries, loads, and boundary conditions; however, the use of classical numerical tools for this problem, like a (six-field) mixed finite element approach, might entail several issues (e.g., shear locking, ill-conditioned matrices, etc.). Conversely, the recently proposed isogeometric collocation method, consisting of the direct discretization of the ODEs in strong form and using the higher-continuity properties typical of spline shape functions, allows an equal order approximation of all unknown fields, without affecting the stability of the solution. This makes such an approach simple, robust, efficient, and particularly suitable for solving the system of ODEs governing the non-prismatic beam problem. Several numerical experiments confirm that the proposed mixed isogeometric collocation method is actually cost-effective and able to attain high accuracy

Factors influencing response to ingenol mebutate therapy for actinic keratosis of face and scalp

AIM To determine factors independently influencing response to ingenol mebutate therapy and assess efficacy on clinical setting of non-hypertrophic non-hyperkeratotic actinic keratosis (AK). METHODS Consecutive patients affected by non-hypertrophic non-hyperkeratotic AKs of the face or scalp were enrolled to receive ingenol mebutate 0.015% gel on a selected skin area of 25 cm2 for 3 consecutive days. Local skin reactions were calculated at each follow up visit using a validated composite score. Efficacy was evaluated by the comparison of clinical and dermoscopic pictures before the treatment and at day 57, and classified as complete, partial and poor response. RESULTS A number of 130 patients were enrolled, of which 101 (77.7%) were treated on the face, while 29 (22.3%) on the scalp. The great majority of our study population (n = 119, 91.5%) reached at least a 75% clearance of AKs and, in particular, 58 patients (44.6%) achieved a complete response while 61 (46.9%) a partial one. Logistic backward multivariate analysis showed that facial localization, level of local skin reaction (LSR) at day 2, the highest LSR values and level of crusts at day 8 were factors independently associated with the achievement of a complete response. CONCLUSION Ingenol mebutate 0.015% gel, when properly applied, is more effective on the face than on the scalp and efficacy is directly associated to LSR score

Interest Rate Targeting and the Dynamics of Short-Term Rates

We explore the link between the overnight fed funds rate, which is actively targeted by the Federal Reserve, and longer-maturity term fed funds rates. We develop a term-structure model which explicitly accounts for interest rate targeting and for the predictability of future target changes. The model is able to replicate some qualitative features of the dynamic behavior of deviations of short-term rates from the target

Asset Price Dynamics and Infrequent Trades

We model an economy where stocks and bonds (consols) are traded by two types of agents: speculators, expected utility maximizers always present in the market, and infrequent traders, whose trading motives are not explicitly modeled. A solution technique for equilibrium prices is developed when trades are triggered by stock prices reaching some threshold level, corresponding to a specific value of the dividend flow. Across trade scenarios we find expectations of stock sales to depress stock prices relative to the no-trade case, while expectations of stock purchases tend to inflate them .both effects bring about heteroskedasticity and predictability of stock returns. Our analysis yields insights as to the equilibrium effects of a variety of trading strategies, which mechanically generate market orders in response to changes in stock prices

Platynereis dumerilii chaetae: mechanical loading estimation from kinematics in larva stage

This work was supported by grant Bio3DPrint from the Austrian Academy of Sciences (OeAW)

A Model of Target Changes and the Term Structure of Interest Rates

We explore the effects of official targeting policy on the term-structure of nominal interest rates, adapting relevant insights from theoretical work on "peso problems" to account for realistic infrequency of target changes. Our analysis of daily U.S. interest rates and newly available historical targets provides an interpretation for persistent spreads between short-term money-market rates and overnight fed-funds targets, and for the poor performance of expectations-hypothesis tests: it is the policy-induced component of fed funds dynamics that appears to be erroneously anticipated by the market. Still, allowance for serial correlation in target changes makes it possible to extract from interest-rate data an expected-knoll series which is quite consistent with the assumptions of the model, indicating that some features of the interest-rate-targeting process are incorporated by market expectations.

Early and Sustained Elevation in Serum Pancreatic Amylase Activity: A Novel Predictor of Morbidity After Pancreatic Surgery

Objective:To characterize early postoperative serum pancreatic amylase (spAMY) trends after pancreatic resections. Summary Background Data:A postoperative spAMY elevation is a common finding but uncertainties remain about its meaning and prognostic implications. Methods:Analysis of patients who consecutively underwent pancreatectomy from 2016 to 2019. spAMY activity was assessed from postoperative day (POD) 0 to 3. Different patterns of spAMY have been identified based on the spAMY standard range (10-52 U/l). Results:Three patterns were identified: (#1) spAMY values always < the lower limit of normal/within the reference range /a single increase in spAMY > upper limit of normal at any POD; (#2) Sustained increase in spAMY activity on POD 0 + 1; (#3) Sustained increase in spAMY activity including POD 1 + 2. Shifting through spAMY patterns was associated with increase morbidity (21% in #1 to 68% in #3 at POD 7; log rank < 0.001). Almost all severe complications (at least Clavien-Dindo >= 3) occurred in patients with pattern #3 (15% vs 3% vs 5% in #1 and #2 at POD 7, P = 0.006), without difference considering >3-times or >the spAMY normal limit (P = 0.85). POPF (9% in #1 vs 48% in #3, P < 0.001) progressively increased across patterns. Pre-operative diabetes (OR 0.19), neoadjuvant therapy (OR 0.22), pancreatic texture (OR 8.8), duct size (OR 0.78), and final histology (OR 2.2) were independent predictors of pattern #3. Conclusions:A sustained increase in spAMY activity including POD 1 + 2 (#3) represents an early postoperative predictor of overall and severe early morbidity. An early and dynamic evaluation of spAMY could crucially impact the subsequent clinical course with relevant prognostic implications

Interest Rate Targeting and the Dynamics of Short-Term Rates

We find that in 1989-1996, when U.S. monetary policy tightly targeted overnight fed funds rates, the volatility and persistence of spreads between target and term fed funds levels were larger for longer-maturity loans. We show that such patterns are consistent with an expectational model where target revisions are infrequent and predictable. In our model, the (autoco-) variance of the spreads of term fed funds rates from the target increases with maturity because longer-term rates are more heavily influenced by persistent expectations of future target changes.