Piezoelectric resonance in Rochelle salt: the contribution of diagonal strains

Within the framework of two-sublattice Mitsui model with taking into account the shear strain $\varepsilon_4$ and the diagonal strains $\varepsilon_2$ and $\varepsilon_3$, a dynamic dielectric response of Rochelle salt X-cuts is considered. Experimentally observed phenomena of crystal clamping by high frequency electric field, piezoelectric resonance and microwave dispersion are described. It is shown that the lowest resonant frequency is always associated with the $\varepsilon_4$ shear modeComment: 17 pages, 6 figure

Review of the species of Trichomalus (Chalcidoidea: Pteromalidae) associated with Ceutorhynchus (Coleoptera: Curculionidae) host species of European origin

Six species of Trichomalus Thomson were reared as parasitoids of Ceutorhynchinae hosts in Europe during surveys in 2000-2004. Trichomalus rusticus (Walker) is treated as a valid species, resurrected from synonymy under T. lucidus (Walker), and T. lyttus (Walker) is transferred from synonymy under T. lucidus and newly placed in synonymy with T. rusticus. Illustrated keys to females and males are given to differentiate the six species (T. bracteatus (Walker), T. campestris (Walker), T. gynetelus (Walker), T. lucidus, T. perfectus (Walker), and T. rusticus) except for males of T. bracteatus and T. gynetelus. A lectotype female is designated for T. rusticus. Trichomalus campestris is newly recorded as a parasitoid of Ceutorhynchus cardariae Korotyaev. Implications of the host-parasitoid associations recovered by the surveys are discussed relative to introduction of species to North America for classical biological contro

The Ising-Kondo lattice with transverse field: an f-moment Hamiltonian for URu2Si2?

We study the phase diagram of the Ising-Kondo lattice with transverse magnetic field as a possible model for the weak-moment heavy-fermion compound URu2Si2, in terms of two low-lying f singlets in which the uranium moment is coupled by on-site exchange to the conduction electron spins. In the mean-field approximation for an extended range of parameters, we show that the conduction electron magnetization responds logarithmically to f-moment formation, that the ordered moment in the antiferromagnetic state is anomalously small, and that the Neel temperature is of the order observed. The model gives a qualitatively correct temperature-dependence, but not magnitude, of the specific heat. The majority of the specific heat jump at the Neel temperature arises from the formation of a spin gap in the conduction electron spectrum. We also discuss the single-impurity version of the model and speculate on ways to increase the specific heat coefficient. In the limits of small bandwidth and of small Ising-Kondo coupling, we find that the model corresponds to anisotropic Heisenberg and Hubbard models respectively.Comment: 20 pages RevTeX including 5 figures (1 in LaTeX, 4 in uuencoded EPS), Received by Phys. Rev. B 19 April 199

Exploring future agricultural development and biodiversity in Uganda, Rwanda and Burundi: a spatially explicit scenario-based assessment

Competition for land is increasing as a consequence of the growing demands for food and other commodities and the need to conserve biodiversity and ecosystem services. Land conversion and the intensification of current agricultural systems continues to lead to a loss of biodiversity and trade-offs among ecosystem functions. Decision-makers need to understand these trade-offs in order to better balance different demands on land and resources. There is an urgent need for spatially explicit information and analyses on the effects of different trajectories of human-induced landscape change in biodiversity and ecosystem services. We assess the potential implications of a set of plausible socio-economic and climate scenarios for agricultural production and demand and model-associated land use and land cover changes between 2005 and 2050 to assess potential impacts on biodiversity in Uganda, Rwanda and Burundi. We show that different future socio-economic scenarios are consistent in their projections of areas of high agricultural development leading to similar spatial patterns of habitat and biodiversity loss. Yet, we also show that without protected areas, biodiversity losses are higher and that expanding protected areas to include other important biodiversity areas can help reduce biodiversity losses in all three countries. These results highlight the need for effective protection and the potential benefits of expanding the protected area network while meeting agricultural production needs

Capability, opportunity, and motivation to enact hygienic practices in the early stages of the COVID‐19 outbreak in the United Kingdom

Objectives The COVID‐19 pandemic is one of the greatest global health threats facing humanity in recent memory. This study aimed to explore influences on hygienic practices, a set of key transmission behaviours, in relation to the Capability, Opportunity, Motivation‐Behaviour (COM‐B) model of behaviour change (Michie et al., 2011). Design Data from the first wave of a longitudinal survey study were used, launched in the early stages of the UK COVID‐19 pandemic. Methods Participants were 2025 adults aged 18 and older, representative of the UK population, recruited by a survey company from a panel of research participants. Participants self‐reported motivation, capability, and opportunity to enact hygienic practices during the COVID‐19 outbreak. Results Using regression models, we found that all three COM‐B components significantly predicted good hygienic practices, with motivation having the greatest influence on behaviour. Breaking this down further, the subscales psychological capability, social opportunity, and reflective motivation positively influenced behaviour. Reflective motivation was largely driving behaviour, with those highest in reflective motivation scoring 51% more on the measure of hygienic practices compared with those with the lowest scores. Conclusions Our findings have clear implications for the design of behaviour change interventions to promote hygienic practices. Interventions should focus on increasing and maintaining motivation to act and include elements that promote and maintain social support and knowledge of COVID‐19 transmission. Groups in particular need of targeting for interventions to increase hygienic practices are males and those living in cities and suburbs

Eco-evolutionary dynamics set the tempo and trajectory of metabolic evolution in multispecies communities

The eco-evolutionary dynamics of microbial communities are predicted to affect both the tempo and trajectory of evolution in constituent species [1]. While community composition determines available niche space, species sorting dynamically alters composition, changing over time the distribution of vacant niches to which species adapt [2], altering evolutionary trajectories [3, 4]. Competition for the same niche can limit evolutionary potential if population size and mutation supply are reduced [5, 6] but, alternatively, could stimulate evolutionary divergence to exploit vacant niches if character displacement results from the coevolution of competitors [7, 8]. Under more complex ecological scenarios, species can create new niches through their exploitation of complex resources, enabling others to adapt to occupy these newly formed niches [9, 10]. Disentangling the drivers of natural selection within such communities is extremely challenging, and it is thus unclear how eco-evolutionary dynamics drive the evolution of constituent taxa. We tracked the metabolic evolution of a focal species during adaptation to wheat straw as a resource both in monoculture and in polycultures wherein on-going eco-evolutionary community dynamics were either permitted or prevented. Species interactions accelerated metabolic evolution. Eco-evolutionary dynamics drove increased use of recalcitrant substrates by the focal species, whereas greater exploitation of readily digested substrate niches created by other species evolved if on-going eco-evolutionary dynamics were prevented. Increased use of recalcitrant substrates was associated with parallel evolution of tctE, encoding a carbon metabolism regulator. Species interactions and species sorting set, respectively, the tempo and trajectory of evolutionary divergence among communities, selecting distinct ecological functions in otherwise equivalent ecosystems

Doping dependence of the resonance peak and incommensuration in high-TcT_{c} superconductors

The doping and frequency evolutions of the incommensurate spin response and the resonance mode are studied based on the scenario of the Fermi surface topology. We use the slave-boson mean-field approach to the $t-t^{\prime}-J$ model and including the antiferromagnetic fluctuation correction in the random-phase approximation. We find that the equality between the incommensurability and the hole concentration is reproduced at low frequencies in the underdoped regime. This equality observed in experiments was explained {\it only} based on the stripe model before. We also obtain the downward dispersion for the spin response and predict its doping dependence for further experimental testing, as well as a proportionality between the low-energy incommensurability and the resonance energy. Our results suggest a common origin for the incommensuration and the resonance peak based on the Fermi surface topology and the d-wave symmetry.Comment: 5 pages, 4 PS figure

Superspace formulations of the (super)twistor string

The superspace formulation of the worldvolume action of twistor string models is considered. It is shown that for the Berkovits-Siegel closed twistor string such a formulation is provided by a N=4 twistor-like action of the tensionless superstring. A similar inverse twistor transform of the open twistor string model (Berkovits model) results in a dynamical system containing two copies of the D=4, N=4 superspace coordinate functions, one left-moving and one right-moving, that are glued by the boundary conditions. We also discuss possible candidates for a tensionful superstring action leading to the twistor string in the tensionless limit as well as multidimensional counterparts of twistor strings in the framework of both `standard' superspace and superspace enlarged by tensorial coordinates (tensorial superspaces), which constitute a natural framework for massless higher spin theories.Comment: Rev Tex, 13 pages, no figure

Anxiety, depression, traumatic stress, and COVID-19 related anxiety in the UK general population during the COVID-19 pandemic

Background The COVID-19 pandemic has created an unprecedented global crisis necessitating drastic changes to living conditions, social life, personal freedom and economic activity. No study has yet examined the presence of psychiatric symptoms in the UK population in similar conditions. Aims We investigated the prevalence of COVID-19 related anxiety, generalised anxiety, depression and trauma symptoms in a representative sample of the UK population during an early phase of the pandemic, and estimated associations with variables likely to influence these symptoms. Method Between March 23rd and March 28th 2020, a quota sample of 2025 UK adults 18 years and older, stratified by age, sex and household income, was recruited by online survey company Qualtrics. Participants completed measures of depression (PHQ9), generalised anxiety (GAD7), and trauma symptoms relating to the pandemic (ITQ). Bivariate and multivariate associations were calculated for age, gender, rural vs urban environment, presence of children in the household, income, loss of income, pre-existing health conditions in self and someone close, infection in self and someone close, and perceived risk of infection over the next month. Results Higher levels of anxiety, depression and trauma symptoms were reported compared to previous population studies, but not dramatically so. Meeting the criteria for either anxiety or depression, and trauma symptoms was predicted by young age, presence of children in the home, and high estimates of personal risk. Anxiety and depression symptoms were also predicted by low income, loss of income, and pre-existing health conditions in self and other. Specific anxiety about COVID-19 was greater in older participants. Conclusions The UK population, especially older citizens, were largely resilient in the early stages of the pandemic. However, several specific COVID-related variables are associated with psychological distress: particularly having children at home, loss of income because of the pandemic, as well as having a pre-existing health condition, exposure to the virus and high estimates of personal risk. Further similar surveys, particularly of those with children at home, are required as the pandemic progresses

Upper critical field for underdoped high-T_c superconductors. Pseudogap and stripe--phase

We investigate the upper critical field in a stripe--phase and in the presence of a phenomenological pseudogap. Our results indicate that the formation of stripes affects the Landau orbits and results in an enhancement of $H_{c2}$. On the other hand, phenomenologically introduced pseudogap leads to a reduction of the upper critical field. This effect is of particular importance when the magnitude of the gap is of the order of the superconducting transition temperature. We have found that a suppression of the upper critical field takes place also for the gap that originates from the charge--density waves.Comment: 7 pages, 5 figure