An approach to permutation symmetry for the electroweak theory

The form of the leptonic mixing matrix emerging from experiment has, in the last few years, generated a lot of interest in the so-called tribimaximal type. This form may be naturally associated with the possibility of a discrete permutation symmetry ($S_3$) among the three generations. However, trying to implement this attractive symmetry has resulted in some problems and it seems to have fallen out of favor. We suggest an approach in which the $S_3$ holds to first approximation, somewhat in the manner of the old SU(3) flavor symmetry of the three flavor quark model. It is shown that in the case of the neutrino sector, a presently large experimentally allowed region can be fairly well described in this first approximation. We briefly discuss the nature of the perturbations which are the analogs of the Gell-Mann Okubo perturbations but confine our attention for the most part to the $S_3$ invariant model. We postulate that the $S_3$ invariant mass spectrum consists of non zero masses for the $(\tau,b,t)$ and zero masses for the other charged fermions but approximately degenerate masses for the three neutrinos. The mixing matrices are assumed to be trivial for the charged fermions but of tribimaximal type for the neutrinos in the first approximation. It is shown that this can be implemented by allowing complex entries for the mass matrix and spontaneous breakdown of the $S_3$ invariance of the Lagrangian.Comment: 24 pages, 1 figure, minor corrections and acknowledgment added. To appear in IJM

Assessing the Impact of Mutations and Horizontal Gene Transfer on the AMR Control: A Mathematical Model

Antimicrobial resistance (AMR) poses a significant threat to public health by increasing mortality, extending hospital stays, and increasing healthcare costs. It affects people of all ages and affects health services, veterinary medicine, and agriculture, making it a pressing global issue. Mathematical models are required to predict the behaviour of AMR and to develop control measures to eliminate resistant bacteria or reduce their prevalence. This study presents a simple deterministic mathematical model in which sensitive and resistant bacteria interact in the environment, and mobile genetic elements (MGEs) are functions that depend on resistant bacteria. We analyze the qualitative properties of the model and propose an optimal control problem in which avoiding mutations and horizontal gene transfer (HGT) are the primary control strategies. We also provide a case study of the resistance and multidrug resistance (MDR) percentages of Escherichia coli to gentamicin and amoxicillin in some European countries using data from the European Antimicrobial Resistance Surveillance Network (EARS-Net). Our theoretical results and numerical experiments indicate that controlling the spread of resistance in southern European regions through the supply of amoxicillin is challenging. However, the host immune system is also critical for controlling AMR.Comment: 1

Structural and thermal characterizations of silica nanoparticles grafted with pendant maleimide and epoxide groups

Grafting of free maleimide and epoxide pendant groups onto the surface of approximately 7-nm silica nanoparticles was investigated. Glycidyloxypropyl groups (3-glycidyloxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane) that carried epoxide groups and aminopropyl groups were grafted to the silica surface with the help of condensation reactions. Maleimide groups [1,1(')-(methylenedi-4,1-phenelene) bismaleimide] were introduced to the silica surface via nucleophilic addition reaction with the aminopropyl groups pre-grafted onto the surface. The grafted silica samples were characterized using CHN, FTIR, DSC, TGA-FTIR, and 13C and 29Si CP/MAS NMR spectroscopy. NMR analyses revealed that all the functional groups were covalently bonded to the silica surface and most of the maleimide and epoxide rings remained intact on surface. DSC analysis showed that the epoxide groups were more reactive than the maleimide groups

Timing of physical activity across adulthood on later-life cognition: 30 years follow-up in the 1946 British birth cohort

BACKGROUND: To assess how timing, frequency and maintenance of being physically active, spanning over 30 years in adulthood, is associated with later-life cognitive function. METHODS: Participants (n=1417, 53% female) were from the prospective longitudinal cohort study, 1946 British birth cohort. Participation in leisure time physical activity was reported five times between ages 36 and 69, categorised into: not active (no participation in physical activity/month); moderately active (participated 1-4 times/month); most active (participated 5 or more times/month). Cognition at age 69 was assessed by tests of cognitive state (Addenbrooke's Cognitive Examination-III), verbal memory (word learning test) and processing speed (visual search speed). RESULTS: Being physically active, at all assessments in adulthood, was associated with higher cognition at age 69. For cognitive state and verbal memory, the effect sizes were similar across all adult ages, and between those who were moderately and most physically active. The strongest association was between sustained cumulative physical activity and later-life cognitive state, in a dose-response manner. Adjusting for childhood cognition, childhood socioeconomic position and education largely attenuated these associations but results mainly remained significant at the 5% level. CONCLUSIONS: Being physically active at any time in adulthood, and to any extent, is linked with higher later-life cognitive state, but lifelong maintenance of physical activity was most optimal. These relationships were partly explained by childhood cognition and education, but independent of cardiovascular and mental health and APOE-E4, suggestive of the importance of education on the lifelong impacts of physical activity

Low power GaAs digital and analog functionalities for microwave signal conditioning in AESA systems

A MMIC demonstrator for RF phase and amplitude control with on board 18-bit serial to parallel conversion (Multi-Functional Chip) is presented. Thanks to an alternative digital building block topology, the DC power consumption of the digital serial to parallel converter is noteworthy: less than 43 mW (2 mW/bit). The main RF performances are 0° - 360° phase coverage and 0 dB - 31.5 dB attenuation setting, in the 7.6 GHz - 9.1 GHz operating bandwidth. The circuit, whose area is 6 mm2, is realised in an industrial and commercially available GaAs technology. This component can be used in active electronically scanned arrays for beam steering

Leptogenesis and μ−τ\mu-\tau symmetry

If an exact $\mu\leftrightarrow \tau$ symmetry is the explanation of the maximal atmospheric neutrino mixing angle, it has interesting implications for origin of matter via leptogenesis in models where small neutrino masses arise via the seesaw mechanism. For seesaw models with two right handed neutrinos $(N_\mu, N_\tau)$, lepton asymmetry vanishes in the exact $\mu\leftrightarrow \tau$ symmetric limit, even though there are nonvanishing Majorana phases in the neutrino mixing matrix. On the other hand, for three right handed neutrino models, lepton asymmetry nonzero and is given directly by the solar mass difference square. We also find an upper bound on the lightest neutrino mass.Comment: 5 pages; latex; no figures; some typos correcte