An Optical Approach to the Dynamical Casimir Effect

We recently proposed a new approach to analyze the parametric resonance in a vibrating cavity based on the analysis of classical optical paths. This approach is used to examine various models of cavities with moving walls. We prove that our method is useful to extract easily basic physical outcome.Comment: 9 page

Exact closed form analytical solutions for vibrating cavities

For one-dimensional vibrating cavity systems appearing in the standard illustration of the dynamical Casimir effect, we propose an approach to the construction of exact closed-form solutions. As new results, we obtain solutions that are given for arbitrary frequencies, amplitudes and time regions. In a broad range of parameters, a vibrating cavity model exhibits the general property of exponential instability. Marginal behavior of the system manifests in a power-like growth of radiated energy.Comment: 17 pages, 7 figure

Exact solution for the energy density inside a one-dimensional non-static cavity with an arbitrary initial field state

We study the exact solution for the energy density of a real massless scalar field in a two-dimensional spacetime, inside a non-static cavity with an arbitrary initial field state, taking into account the Neumann and Dirichlet boundary conditions. This work generalizes the exact solution proposed by Cole and Schieve in the context of the Dirichlet boundary condition and vacuum as the initial state. We investigate diagonal states, examining the vacuum and thermal field as particular cases. We also study non-diagonal initial field states, taking as examples the coherent and Schrodinger cat states.Comment: 10 pages, 8 figure

Vibrating Cavities - A numerical approach

We present a general formalism allowing for efficient numerical calculation of the production of massless scalar particles from vacuum in a one-dimensional dynamical cavity, i.e. the dynamical Casimir effect. By introducing a particular parametrization for the time evolution of the field modes inside the cavity we derive a coupled system of first-order linear differential equations. The solutions to this system determine the number of created particles and can be found by means of numerical methods for arbitrary motions of the walls of the cavity. To demonstrate the method which accounts for the intermode coupling we investigate the creation of massless scalar particles in a one-dimensional vibrating cavity by means of three particular cavity motions. We compare the numerical results with analytical predictions as well as a different numerical approach.Comment: 28 pages, 19 figures, accepted for publication in J. Opt. B: Quantum Semiclass. Op

Numerical approach to the dynamical Casimir effect

The dynamical Casimir effect for a massless scalar field in 1+1-dimensions is studied numerically by solving a system of coupled first-order differential equations. The number of scalar particles created from vacuum is given by the solutions to this system which can be found by means of standard numerics. The formalism already used in a former work is derived in detail and is applied to resonant as well as off-resonant cavity oscillations.Comment: 15 pages, 4 figures, accepted for publication in J. Phys. A (special issue: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 2005

Mixed Manufacturer Combination With a Cementless Hemispherical Dual Mobility Cup and Polished Taper-Slip Cemented Femoral Stem: Short- to Medium-Term Results in Primary Total Hip Arthroplasty in Elderly Patients.

There is a lack of conclusive literature regarding the mixed-manufacturer combination of the Symbol cementless hemispherical dual mobility cup (Dedienne Santé) and the Exeter V40 cemented femoral stems (Stryker) in patients who underwent primary total hip arthroplasty (THA). This study aimed to evaluate the clinical and radiographic outcomes of this combination, with a particular attention to the occurrence of dislocation and periprosthetic femoral fractures (PFFs). Between 2021 and 2023, a consecutive series of 123 primary THAs were reviewed at the latest follow-up. The mean age at surgery was 75 ± 9 ys. Postoperative complications were recorded. The clinical outcome was assessed with the Harris Hip Score. Acetabular, femoral, and global hip offset were evaluated on standard radiographs. At a mean follow-up of 23 ± 7 months, the mean preoperative to postoperative Harris Hip Score improved significantly from 46 to 93 (P < .0001.) No dislocation was reported. No Vancouver A or B PFF was observed. One Vancouver C PFF was observed. The revision-free survival rate at 24-month follow-up was 98.6%. The global offset of the hip was restored in all the patients with a mean average increase of 3 ± 5.8 mm. The mixed-manufacturer combination of the Symbol cementless hemispherical dual mobility cup and the Exeter cemented femoral stem resulted in excellent short- to medium-term outcomes in patients who underwent primary THA. This combination was effective in preventing both instability and femoral Vancouver B PFF in these patients at risk, while allowing global hip offset restoration

Extra N-Terminal Residues Have a Profound Effect on the Aggregation Properties of the Potential Yeast Prion Protein Mca1

The metacaspase Mca1 from Saccharomyces cerevisiae displays a Q/N-rich region at its N-terminus reminiscent of yeast prion proteins. In this study, we show that the ability of Mca1 to form insoluble aggregates is modulated by a peptide stretch preceding its putative prion-forming domain. Based on its genomic locus, three potential translational start sites of Mca1 can give rise to two slightly different long Mca1 proteins or a short version, Mca1451/453 and Mca1432, respectively, although under normal physiological conditions Mca1432 is the predominant form expressed. All Mca1 variants exhibit the Q/N-rich regions, while only the long variants Mca1451/453 share an extra stretch of 19 amino acids at their N-terminal end. Strikingly, only long versions of Mca1 but not Mca1432 revealed pronounced aggregation in vivo and displayed prion-like properties when fused to the C-terminal domain of Sup35 suggesting that the N-terminal peptide element promotes the conformational switch of Mca1 protein into an insoluble state. Transfer of the 19 N-terminal amino acid stretch of Mca1451 to the N-terminus of firefly luciferase resulted in increased aggregation of luciferase, suggesting a protein destabilizing function of the peptide element. We conclude that the aggregation propensity of the potential yeast prion protein Mca1 in vivo is strongly accelerated by a short peptide segment preceding its Q/N-rich region and we speculate that such a conformational switch might occur in vivo via the usage of alternative translational start sites

Robust automated detection of microstructural white matter degeneration in Alzheimer’s disease using machine learning classification of multicenter DTI data

Diffusion tensor imaging (DTI) based assessment of white matter fiber tract integrity can support the diagnosis of Alzheimer’s disease (AD). The use of DTI as a biomarker, however, depends on its applicability in a multicenter setting accounting for effects of different MRI scanners. We applied multivariate machine learning (ML) to a large multicenter sample from the recently created framework of the European DTI study on Dementia (EDSD). We hypothesized that ML approaches may amend effects of multicenter acquisition. We included a sample of 137 patients with clinically probable AD (MMSE 20.6±5.3) and 143 healthy elderly controls, scanned in nine different scanners. For diagnostic classification we used the DTI indices fractional anisotropy (FA) and mean diffusivity (MD) and, for comparison, gray matter and white matter density maps from anatomical MRI. Data were classified using a Support Vector Machine (SVM) and a Naïve Bayes (NB) classifier. We used two cross-validation approaches, (i) test and training samples randomly drawn from the entire data set (pooled cross-validation) and (ii) data from each scanner as test set, and the data from the remaining scanners as training set (scanner-specific cross-validation). In the pooled cross-validation, SVM achieved an accuracy of 80% for FA and 83% for MD. Accuracies for NB were significantly lower, ranging between 68% and 75%. Removing variance components arising from scanners using principal component analysis did not significantly change the classification results for both classifiers. For the scanner-specific cross-validation, the classification accuracy was reduced for both SVM and NB. After mean correction, classification accuracy reached a level comparable to the results obtained from the pooled cross-validation. Our findings support the notion that machine learning classification allows robust classification of DTI data sets arising from multiple scanners, even if a new data set comes from a scanner that was not part of the training sample

Total hip arthroplasty through the direct anterior approach with and without the use of a traction table: a matched-control, retrospective, single-surgeon study.

Hip surgeons performing total hip arthroplasty (THA) through the direct anterior approach (DAA) commonly use a traction table to facilitate exposure. Even though performing THA through DAA without a traction table could be technically more demanding, this technique offers the advantage of intraoperative leg length comparison. Therefore, this study aimed to compare clinical outcomes, complication rates, component positioning, and leg length discrepancy (LLD) after THA through the DAA performed with or without a traction table. A single-surgeon continuous series of 75 patients who underwent DAA THA performed with a traction table was matched for gender, age, and BMI with 75 patients who underwent DAA THA performed without a traction table (male, 62; female, 88, with an average age of 68 years old). Clinical and radiological outcomes, intra- and postoperative complications, and LLD were retrospectively assessed. No statistically significant difference was detected in surgical time, hospital stay, Harris Hip Score (HHS), complication rates, and implant positioning between the two groups. Leg length restoration was significantly more accurate in the group performed without a traction table (2.4 ± 2 mm vs. 3.7 ± 3.1 mm; p value ≤ 0.05). No LLD > 10 mm was reported in the group performed without a traction table, whereas two cases (2.7%) were reported in those performed with a traction table. Performing THA through DAA without a traction table was associated with a significantly more accurate leg length restoration without a significant increase in the rates of intra- and postoperative complications

Varieties of living things: Life at the intersection of lineage and metabolism

publication-status: Publishedtypes: Articl