Generalized energy equipartition in harmonic oscillators driven by active baths

We study experimentally and numerically the dynamics of colloidal beads confined by a harmonic potential in a bath of swimming E. coli bacteria. The resulting dynamics is well approximated by a Langevin equation for an overdamped oscillator driven by the combination of a white thermal noise and an exponentially correlated active noise. This scenario leads to a simple generalization of the equipartition theorem resulting in the coexistence of two different effective temperatures that govern dynamics along the flat and the curved directions in the potential landscape.Comment: 4 pages, 3 figure

SGDE: Secure Generative Data Exchange for Cross-Silo Federated Learning

Privacy regulation laws, such as GDPR, impose transparency and security as design pillars for data processing algorithms. In this context, federated learning is one of the most influential frameworks for privacy-preserving distributed machine learning, achieving astounding results in many natural language processing and computer vision tasks. Several federated learning frameworks employ differential privacy to prevent private data leakage to unauthorized parties and malicious attackers. Many studies, however, highlight the vulnerabilities of standard federated learning to poisoning and inference, thus raising concerns about potential risks for sensitive data. To address this issue, we present SGDE, a generative data exchange protocol that improves user security and machine learning performance in a cross-silo federation. The core of SGDE is to share data generators with strong differential privacy guarantees trained on private data instead of communicating explicit gradient information. These generators synthesize an arbitrarily large amount of data that retain the distinctive features of private samples but differ substantially. In this work, SGDE is tested in a cross-silo federated network on images and tabular datasets, exploiting beta-variational autoencoders as data generators. From the results, the inclusion of SGDE turns out to improve task accuracy and fairness, as well as resilience to the most influential attacks on federated learning

Colloidal transport by light induced gradients of active pressure

The mechanical forces exerted by active fluids may provide an effective way of transporting microscopic objects, but the details remain elusive. Using space modulated activity, Pellicciotta et al. generate active pressure gradients capable of transporting passive particles in controlled directions.Active fluids, like all other fluids, exert mechanical pressure on confining walls. Unlike equilibrium, this pressure is generally not a function of the fluid state in the bulk and displays some peculiar properties. For example, when activity is not uniform, fluid regions with different activity may exert different pressures on the container walls but they can coexist side by side in mechanical equilibrium. Here we show that by spatially modulating bacterial motility with light, we can generate active pressure gradients capable of transporting passive probe particles in controlled directions. Although bacteria swim faster in the brighter side, we find that bacteria in the dark side apply a stronger pressure resulting in a net drift motion that points away from the low activity region. Using a combination of experiments and numerical simulations, we show that this drift originates mainly from an interaction pressure term that builds up due to the compression exerted by a layer of polarized cells surrounding the slow region. In addition to providing new insights into the generalization of pressure for interacting systems with non-uniform activity, our results demonstrate the possibility of exploiting active pressure for the controlled transport of microscopic objects

Velocity distribution in active particles systems

We derive an analytic expression for the distribution of velocities of multiple interacting active particles which we test by numerical simulations. In clear contrast with equilibrium we find that the velocities are coupled to positions. Our model shows that, even for two particles only, the individual velocities display a variance depending on the interparticle separation and the emergence of correlations between the velocities of the particles. When considering systems composed of many particles we find an analytic expression connecting the overall velocity variance to density, at the mean-field level, and to the pair distribution function valid in the limit of small noise correlation times. Finally we discuss the intriguing analogies and main differences between our effective free energy functional and the theoretical scenario proposed so far for phase-separating active particles

Uterine and ovarian changes during testosterone administration in young female-to-male transsexuals

Abstract Objective Female-to-male transition remains a specific clinical indication for long-term testosterone administration. There is a limited number of studies dealing with the effect of androgen treatment on their female receptive targets (mainly breast and uterus) and the knowledge in this field is scarce and, sometimes, contradictory. Materials and Methods We performed a prospective study including 12 patients aged between 20 years and 32 years, with a diagnosis of gender dysphoria, treated with parenteral testosterone administration before sexual reassignment surgery. Results Endometrial histology revealed the presence of active endometrium in 10 cases and secretive endometrium in two cases. Multifollicular ovaries were observed in all cases of active endometrium, while corpus luteum was present in the two cases of secretory endometrium. Fibroids or hypertrophic myometrium were observed in 58% of the patients. Estrogen receptor was very high (59%) in the endometrial epithelial cells and low (17%) in the myometrium. Androgen receptor expression was modest in endometrial epithelial cells (24%) and sustained in myometrium (69%). Ki67 expression is steadily present in all uterine compartments, varying from 8% in epithelial endometrium to 2% in the myometrium. Conclusion Our data suggest that long-term testosterone administration to female-to-male patients during reproductive age induces a low proliferative active endometrium, associated with some hypertrophic myometrial changes

An insight into the reactivity of the electrogenerated radical cation of caffeine

Controlled potential electrolyses of caffeine (CAF) were carried out at a Pt electrode in undried acetonitrile (ACN) and ACN-H2O and the products of the anodic oxidation were analyzed by HPLC-PDA-ESI-MS/MS. A higher current efficiency occurred in ACN-H2O, but an analogous chromatographic outline was found in both media, evidencing a reactive pathway of the electrogenerated radical cation CAF•+ with water, added or in trace, as nucleophile. No dimeric forms were evidenced, excluding any coupling reactions. Neither was 1,3,7-trimethyluric acid found, reported in the literature as the main oxidative route for CAF in water. Four main chromatographic peaks were evidenced, assigned to four proposed structures on the base of chromatographic and spectral data: a 4,5-diol derivative and an oxazolidin-2-one derivative were assigned as principal oxidation products, supporting a mechanism proposed in a previous work for the primary anodic oxidation of the methylxanthines olefinic C4 = C 5 bond. Two highly polar degradation products were also tentatively assigned, that seemed generating along two different pathways, one opening the imidazolic moiety and another one opening the purinic one

Direct Anterior Approach in Total Hip Arthroplasty for Severe Crowe IV Dysplasia: Retrospective Clinical and Radiological Study

Background and Objectives: total hip arthroplasty (THA) for Crowe IV hip dysplasia poses challenges due to severe leg shortening, muscle retraction and bone stock issues, leading to an increased neurological complication, and revision rate. The direct anterior approach (DAA) is used for minimally invasive THA but its role in Crowe IV dysplasia is unclear. This retrospective study examines if DAA effectively restores hip biomechanics in Crowe IV dysplasia patients with <4 cm leg length discrepancy, managing soft tissue and yielding functional improvement, limb length correction, and limited complications. Materials and Methods: 19 patients with unilateral Crowe IV hip osteoarthritis and <4 cm leg length discrepancy undergoing DAA THA were reviewed. Surgery involved gradual soft tissue release, precise acetabular cup positioning, and stem placement without femoral osteotomy. Results: results were evaluated clinically and radiographically, with complications recorded. Follow-up revealed significant Harris Hip Score and limb length discrepancy improvements. Abductor muscle insufficiency was present in 21%. The acetabular component was accurately placed, centralizing the prosthetic joint's rotation. Complications occurred in 16% of cases, including fractures, nerve issues, and infection. DAA in THA showcased positive outcomes for hip function, limb length, and biomechanics in Crowe IV dysplasia. Conclusions: the technique enabled accurate cup positioning and rotation center adjustment. Complications were managed well without implant revisions. DAA is a viable option for Crowe IV dysplasia, restoring hip function, biomechanics, and reducing limb length discrepancy. Larger, longer studies are needed for validation