Hybrid LTA vehicle controllability as affected by buoyancy ratio

The zero and low speed controllability of heavy lift airships under various wind conditions as affected by the buoyancy ratio are investigated. A series of three hybrid LTA vehicls were examined, each having a dynamic thrust system comprised of four H-34 helicopters, but with buoyant envelopes of different volumes (and hence buoyancies), and with varying percentage of helium inflation and varying useful loads (hence gross weights). Buoyancy ratio, B, was thus examined varying from approximately 0.44 to 1.39. For values of B greater than 1.0, the dynamic thrusters must supply negative thrust (i.e. downward)

New Developments of Laser Desorption Ionization Mass Spectrometry in Plant Analysis

The structural identification of natural products is one of the major focus areas of analytical chemistry research. Mass spectrometry (MS) has long been used to obtain molecular weights and further molecular formulae. In the past, former ionization sources such as electronic impact unfortunately limited MS analysis to predominately volatile, polar, and thermostable compounds. However, recent developments in soft ionization techniques such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), or laser desorption/ionization (LDI) have gradually extended MS analysis to a much wide range of chemical structures. As far as small natural compounds are concerned, LDI sources are still seldom used because of specific technical limitations. Indeed, the photoionization process of LDI is generally assisted by a matrix, which is a small molecule carrying strong UV chromophore. The process is then called matrix‐assisted laser desorption/ionization (MALDI) process. MALDI ionization therefore induces the formation of numerous matrix ions that commonly appear in the range 0–600 Da, and consequently interfere with molecular ions originating from many natural products. For this reason, the correct signal assignment is highly impaired in the critical region of interest. As LDI and MALDI are not only soft ionization processes but also quite sensitive techniques yielding high resolution spectra when coupled to a time‐of‐flight (TOF) analyzer, different attempts have been made to adapt these techniques for the analysis of natural products. Three of them will be more specifically discussed in this chapter: (i) LDI on neat gold surfaces obtained by physical vapor diffusion (PVD), (ii) desorption/ionization on self‐assembled monolayer surfaces (DIAMS), and (iii) the use of specific matrices for the selective detection of alkaloids

Predicting the size and probability of epidemics in a population with heterogeneous infectiousness and susceptibility

We analytically address disease outbreaks in large, random networks with heterogeneous infectivity and susceptibility. The transmissibility $T_{uv}$ (the probability that infection of $u$ causes infection of $v$) depends on the infectivity of $u$ and the susceptibility of $v$. Initially a single node is infected, following which a large-scale epidemic may or may not occur. We use a generating function approach to study how heterogeneity affects the probability that an epidemic occurs and, if one occurs, its attack rate (the fraction infected). For fixed average transmissibility, we find upper and lower bounds on these. An epidemic is most likely if infectivity is homogeneous and least likely if the variance of infectivity is maximized. Similarly, the attack rate is largest if susceptibility is homogeneous and smallest if the variance is maximized. We further show that heterogeneity in infectious period is important, contrary to assumptions of previous studies. We confirm our theoretical predictions by simulation. Our results have implications for control strategy design and identification of populations at higher risk from an epidemic.Comment: 5 pages, 3 figures. Submitted to Physical Review Letter

COVID-19 vaccine skeptics are persuaded by pro-vaccine expert consensus messaging

To further understand how to combat COVID-19 vaccination hesitancy, we examined the effects of pro-vaccine expert consensus messaging on lay attitudes about vaccine safety and intention to get a COVID-19 vaccine. We surveyed 729 unvaccinated individuals from four countries in the early stages of the pandemic and 472 unvaccinated individuals from two countries after 2 years of the pandemic. We found belief of vaccine safety strongly correlated with intention to vaccinate in the first sample and less strongly in the second. We also found that consensus messaging improved attitudes toward vaccination even for participants who did not believe the vaccine is safe nor intended to get it. The persuasiveness of expert consensus was unaffected by exposing participants’ lack of knowledge about vaccines. We conclude that highlighting expert consensus may be a way to increase support toward COVID-19 vaccination in those hesitant or skeptical.info:eu-repo/semantics/acceptedVersio

Some homogenization and corrector results for nonlinear monotone operators

This paper deals with the limit behaviour of the solutions of quasi-linear equations of the form \ \ds -\limfunc{div}\left(a\left(x, x/{\varepsilon _h},Du_h\right)\right)=f_h on $\Omega$ with Dirichlet boundary conditions. The sequence $(\varepsilon _h)$ tends to $0$ and the map $a(x,y,\xi )$ is periodic in $y$, monotone in $\xi$ and satisfies suitable continuity conditions. It is proved that $u_h\rightarrow u$ weakly in $H_0^{1,2}(\Omega )$, where $u$ is the solution of a homogenized problem \ -\limfunc{div}(b(x,Du))=f on $\Omega$. We also prove some corrector results, i.e. we find $(P_h)$ such that $Du_h-P_h(Du)\rightarrow 0$ in $L^2(\Omega ,R^n)$