892 research outputs found
Dual polarization operation of nanostructure arrays in the MIR region
In this paper, we report on arrays of asymmetric split H-shape nanostructures tuned to produce two distinct resonances at wavelengths that range from 3 μm to 7 μm. The electric-field of the incident wave has been both polarized parallel to the vertical asymmetric dipole arms and polarized across the 50 nm gap in the asymmetric horizontal bar. We have produced resonance quality factors as large as 26 in the mid-infrared region
Unambiguous evaluation of the relative photolysis rates of nitro indolinyl protecting groups critical for brain network studies
AbstractNitrated indolinyl photoprotecting groups are crucial tools extensively used in the study of neuronal signal transduction. Mononitrated photolabile protecting groups have been used effectively, however, recent advances in the introduction of a second nitro group have shown improvement in the photo efficiency of neurotransmitter (agonist) release, albeit, to varying extents, depending on the assessment methods employed. An unambiguous method is discussed based on Nuclear Magnetic Resonance (NMR), which is shown to be an effective technique in the relative overall rate comparison amongst varying nitrated protecting groups. Mononitrated and dinitrated photolabile protecting groups such as CDNI-Glu and MNI-Glu are used as an example to assess the relative value of adding a second nitro group in photoactive cage designs. Using this technique, it was shown that the second nitro group in CDNI systems enhances the overall relative rate of photocleavage by a factor of 5.8. This reported method can also be used to unambiguously determine relative rate of agonist photorelease
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 () 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 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 invariant model. We postulate that the invariant mass
spectrum consists of non zero masses for the 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 invariance of the
Lagrangian.Comment: 24 pages, 1 figure, minor corrections and acknowledgment added. To
appear in IJM
Mathematical modelling of the first HIV/ZIKV co-infection cases in Colombia and Brazil
This paper presents a mathematical model to investigate co-infection with
HIV/AIDS and zika virus (ZIKV) in Colombia and Brazil, where the first cases
were reported in 2015-2016. The model considers the sexual transmission
dynamics of both viruses and vector-host interactions. We begin by exploring
the qualitative behaviour of each model separately. Then, we analyze the
dynamics of the co-infection model using the thresholds and results defined
separately for each model. The model also considers the impact of intervention
strategies, such as, personal protection, antiretroviral therapy (ART), and
sexual protection (condoms use). Using available parameter values for Colombia
and Brazil, the model is calibrated to predict the potential effect of
implementing combinations of those intervention strategies on the co-infection
spread. According to these findings, transmission through sexual contact is a
determining factor in the long-term behaviour of these two diseases.
Furthermore, it is important to note that co-infection with HIV and ZIKV may
result in higher rates of HIV transmission and an increased risk of severe
congenital disabilities linked to ZIKV infection. As a result, control measures
have been implemented to limit the number of infected individuals and
mosquitoes, with the aim of halting disease transmission. This study provides
novel insights into the dynamics of HIV/ZIKV co-infection and highlights the
importance of integrated intervention strategies in controlling the spread of
these viruses, which may impact public healt
Accounting for Channeling and Shielding Effects for Vapor Cloud Explosions
PresentationVapor cloud explosions (VCEs) can cause significant damage to nearby buildings, facilities and infrastructure with potential loss of life and significant business interruption, so the accuracy of predicting blast loads on facility buildings is critical in estimating these losses. Closely spaced buildings and process equipment outside of the congested region of a VCE provide a complicated flow field for an expanding blast wave. Their presence can channel and shield the blast flow field, resulting in significant effects on the blast load magnitude and wave form shape. Currently, the most common way to estimate applied blast pressures resulting from VCE’s is to use simplified methods that account for the total energy from the stoichiometric portion of the vapor cloud, fuel reactivity, and level of congestion and confinement, such as the TNO Multi-energy, equivalent TNT, CAM, and BST methods. These simplified tools are based on unobstructed line-of-site conditions, which can overestimate and/or underestimate blast loads. This presentation illustrates the use of a fast- running Computational Fluid Dynamic (CFD) approach that can account for channeling and shielding effects without having to use a turbulent combustion model. This approach provides a convenient tool for designers and process safety planners to more accurately quantify the hazard from postulated VCE hazards that include site-specific channeling and shielding effects. The accuracy of the approach is demonstrated via comparisons of CFD simulations to experimentally measured waveforms. Computed pressure and impulse are also compared to the BST predictions for unobstructed and obstructed sites
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
Effect of the drying techniques on the morphology of silica nanoparticles synthesized via sol–gel process
The effect of drying techniques on the dispersion and agglomeration of silica nanoparticles were studied using alcohol-dehydration (AD), freeze-drying (FD) and oven drying (OD) techniques. Observation under optical microscope showed that aqueous-dispersion with OD technique led to the formation of densely packed particles (islands) while AD resulted in loosely packed particles with non-isotropic aggregation pattern. TEM analysis showed that most of the silica nanoparticles were homogenous and discrete in nature. The comparison between experimental (SBET) and theoretical (Sspherical) surface area indicated that the agglomeration of nanoparticles increased in the order of AD FD > OD and the increase in the pore size (Dp) and pore volume (Vp) in the order of AD < FD < OD further supports the agglomeration trend predicted by the surface area comparison. The results suggested that agglomeration can be effectively reduced by eliminating water from the system before solidification since the presence of water during the process could intense the interparticle interactions leading to agglomeration. Overall a new, simple and cost effective drying technique (AD) has been developed to produce silica nanoparticles with improved dispersion and reduced agglomeration
Timing of physical activity across adulthood on later-life cognition: 30 years follow-up in the 1946 British birth cohort
Background:Â 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:Â 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:Â 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
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
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