Spin-boson dynamics: A unified approach from weak to strong coupling

We present a novel approximation scheme to describe the influence of a harmonic bath on the dynamics of a two-level particle over almost the whole regime of temperatures and coupling to the environment, for a wide class of bath spectral densities. Starting from the exact path-integral solution for the two-level system density matrix, effective intra-blip correlations are fully included, while inter-blip and blip-sojourn interactions are considered up to first order. In the proper regimes, an excellent agreement with conventional perturbative approaches and ab-initio path-integral results is found.Comment: 6 pages, 4 figures (enlarged figures and minor changes to the text

Spin-boson dynamics beyond conventional perturbation theories

A novel approximation scheme is proposed to describe the dynamics of the spin-boson problem. Being nonperturbative in the coupling strength nor in the tunneling frequency, it gives reliable results over a wide regime of temperatures and coupling strength to the thermal environment for a large class of bath spectral densities. We use a path-integral approach and start from the exact solution for the two-level system population difference in the form of a generalized master equation (GME). Then, we approximate inter-blip and blip-sojourns interactions up to linear order, while retaining all intra-blip correlations to find the kernels entering the GME in analytical form. Our approximation scheme, which we call Weakly-Interacting Blip Approximation (WIBA), fully agrees with conventional perturbative approximations in the tunneling matrix element (Non-Interacting Blip Approximation) or in the system-bath coupling strength.Comment: 15 pages, 14 figure

Stand structure and anatomical, physical and mechanical characterisation of sessile oak (Quercus petraea Liebl.) wood from central Italy aged coppices.

The present paper aims to implement the knowledge on sessile oak (Quercus petraea (Matt.) Liebl.) in Mediterranean area where, although present, for natural or anthropogenic causes, the species is rare. The focus is on two sessile oak stands in Tuscany (central Italy), classified as worthy of protection for their importance both in a local-national and European context. In addition to the environmental and stand structural characteristics, some technological properties of sessile oak wood grown there, comparing the obtained results to the bibliographic data were provided. The examined wood characteristics are anatomical parameters (growth ring thickness, earlywood and latewood thickness, fiber length, earlywood and latewood vessel diameter, amount of earlywood and latewood vessel) and the physical and mechanical parameters (density, modulus of elasticity, strength, hardness). No appreciable technological differences issued between the examined wood in the two stands and the wood from the same species, but from other Italian and French provenances, obtained from literature. Results highlighted, although managed as coppice in the past, the material is suitable for the reforestation of this endangered species in suitable areas, always taking into account that the quality of the wood is determined not only by the basic technological properties of a certain wood, but also, and mostly, by the growing conditions of the trees and particularly by the sylvicultural management of the stand

Does the continuation of low-dose acetylsalicylic acid during the perioperative period of thyroidectomy increase the risk of cervical haematoma? A 1-year experience of two Italian centers

Background: A growing number of patients taking antiplatelet drugs, mainly low-dose acetylsalicylic acid (ASA) (75–150 mg/day), for primary or secondary prevention of thrombotic events, are encountered in every field of surgery. While the bleeding risk due to the continuation of these medications during the perioperative period has been adequately investigated in several surgical specialties, in thyroid surgery it still needs to be clarified. The main aim of this study was to assess the occurrence of cervical haematoma in patients receiving low-dose acetylsalicylic acid, specifically ASA 100 mg/day, during the perioperative period of thyroidectomy. Methods: Patients undergoing thyroidectomy in two high-volume thyroid surgery centers in Italy, between January 2021 and December 2021, were retrospectively analysed. Enrolled patients were divided into two groups: those not taking ASA were included in Group A, while those receiving this drug in Group B. Univariate analysis was performed to compare these two groups. Moreover, multivariate analysis was employed to evaluate the use of low-dose ASA as independent risk factor for cervical haematoma. Results: A total of 412 patients underwent thyroidectomy during the study period. Among them, 29 (7.04%) were taking ASA. Based on the inclusion criteria, 351 patients were enrolled: 322 were included in Group A and 29 in Group B. In Group A, there were 4 (1.24%) cervical haematomas not requiring surgical revision of haemostasis and 4 (1.24%) cervical haematomas requiring surgical revision of haemostasis. In Group B, there was 1 (3.45%) cervical haematoma requiring surgical revision of haemostasis. At univariate analysis, no statistically significant difference was found between the two groups in terms of occurrence of cervical haematoma, nor of the other early complications of thyroidectomy. At multivariate analysis, the use of low-dose ASA did not prove to be an independent risk factor for cervical haematoma. Conclusions: Based on our findings, we believe that in patients receiving this drug, either for primary or secondary prevention of thrombotic events, its discontinuation during the perioperative period of thyroidectomy is not necessary

Micro-chemical evaluation of ancient potsherds by μ-LIBS scanning on thin section negatives

In the study of ancient pottery, thin section analysis represents the basic approach to study mineralogical and petrografic features in order to obtain preliminary information about the production technology and origin of archaeological ceramics. However, even if thin section analysis allows investigating the textural and structural characteristics of potteries, peculiar features related to clay paste and temper composition, as well as provenance issues, can be detailed addressed only by quantitative mineralogical and chemical studies. In the realization of thin sections, a negative face is always produced, similar to the thin section itself; these remains can be used for additional analyses, such as high spatial resolution micro-chemical studies using, for example, a micro-laser induced breakdown spectroscopy (LIBS) scanner. LIBS is a spectroscopic technique that, exploiting the laser radiation, is able to bring into the plasma state micrometric portions of the sample, and to analyse its content through the study of the optical emission of the plasma itself. Unlike other techniques, LIBS can detect and quantify also light elements such as aluminium and magnesium. Images produced by the micro-LIBS instrument show the spatial distribution of the chemical elements within a portion of the sample, which may have dimensions from a few hundred microns up to several centimeters. The combination of these images with algorithms derived from image processing techniques may return interesting information and supporting data to in-depth investigate pottery components detected by optical microscopy observations. In this work, we present the results of an experimental study performed on thin-section negatives with different grain size, surface treatments and aggregates, coming from some Neolithic Italian sites, exploring the potential of the LIBS method in micro-chemical studies of ancient potsherds

Multivariate calibration in Laser-Induced Breakdown Spectroscopy quantitative analysis: The dangers of a ‘black box’ approach and how to avoid them

The introduction of multivariate calibration curve approach in Laser-Induced Breakdown Spectroscopy (LIBS) quantitative analysis has led to a general improvement of the LIBS analytical performances, since a multivariate approach allows to exploit the redundancy of elemental information that are typically present in a LIBS spectrum. Software packages implementing multivariate methods are available in the most diffused commercial and open source analytical programs; in most of the cases, the multivariate algorithms are robust against noise and operate in unsupervised mode. The reverse of the coin of the availability and ease of use of such packages is the (perceived) difficulty in assessing the reliability of the results obtained which often leads to the consideration of the multivariate algorithms as ‘black boxes’ whose inner mechanism is supposed to remain hidden to the user. In this paper, we will discuss the dangers of a ‘black box’ approach in LIBS multivariate analysis, and will discuss how to overcome them using the chemical-physical knowledge that is at the base of any LIBS quantitative analysis

Estimating Prognosis and Frailty in Persons Aged ≥75 Years in the Emergency Department: Further Validation of Dynamic Silver Code.

OBJECTIVES To assess concurrent validity of the Dynamic Silver Code (DSC), a tool based on administrative data that predicts prognosis in older adults accessing the emergency department (ED), in terms of association with markers of poor functional and cognitive status. DESIGN Cross-sectional. SETTING AND PARTICIPANTS Data were obtained in the AIDEA study, which enrolled a cohort of ≥75-year-old patients, accessing the ED of 2 hospitals in Florence, Italy. METHODS The DSC score and classes (I to IV, corresponding to an increasing risk of death) were obtained from administrative data. Information on health and functional status prior to ED access were collected from face-to-face, direct, or proxy interviews. The 4AT test was administered to screen for possible delirium. Bivariate comparisons of the prevalence of each functional and cognitive marker across 4 DSC classes were performed. Multinomial logistic regression was used to assess the multivariable risk of being in II, III, or IV DSC class vs I. RESULTS Among 3358 participants (mean age 83 years, men 44%), 32.9%, 30.3%, 19.5%, and 17.2% were in DSC class I, II, III, and IV. Preadmission abnormal functional and cognitive conditions, and delirium in the ED, were increasingly more common from DSC class I through IV (P < .001). In particular, the prevalence of total inability to walk increased from 2.9% (class I) to 23.4% (class IV). In multivariable analyses, this was the strongest predictor of being in progressively worse DSC classes, whereas feeling of exhaustion, reporting of serious falls, weight loss, and severe memory loss or diagnosis of dementia gave some contribution. CONCLUSIONS AND IMPLICATIONS The ability of the DSC to predict survival in older persons appears to rely on its prevailing association with markers of functional impairment. These results may support clinical use of the tool