High resolution spectroscopy in the microwave and far infrared

High resolution rotational spectroscopy has long been central to remote sensing techniques in atmospheric sciences and astronomy. As such, laboratory measurements must supply the required data to make direct interpretation of data for instruments which sense atmospheres using rotational spectra. Spectral measurements in the microwave and far infrared regions are also very powerful tools when combined with infrared measurements for characterizing the rotational structure of vibrational spectra. In the past decade new techniques were developed which have pushed high resolution spectroscopy into the wavelength region between 25 micrometers and 2 mm. Techniques to be described include: (1) harmonic generation of microwave sources, (2) infrared laser difference frequency generation, (3) laser sideband generation, and (4) ultrahigh resolution interferometers

Method and means for generation of tunable laser sidebands in the far-infrared region

A method for generating tunable far-infrared radiation is described. The apparatus includes a Schottky-barrier diode which has one side coupled through a conductor to a waveguide that carries a tunable microwave frequency; the diode has an opposite side which is coupled through a radiating whisker to a bias source. Infrared light is directed at the diode, and infrared light with tunable sidebands is radiated by the whisker through an open space to a reflector. The original infrared is separated from a tunable infrared sideband by a polarizing Michelson interferometer

Examining the differences between university students' levels of resilience on mindfulness, psychological distress and coping strategies

University students can face numerous stressors which can contribute to the development of psychological distress shown to be associated with decreasing completion and retention issues throughout Australian universities (Willcoxson, Cotter, & Joy, 2011). A positive predictor and outcome of successful student coping and adjustment to university and retention outcomes is resilience, the ability to cope in difficult situations and bounce back from adversity. Mindfulness has also been shown to be promote resilience. The present study examined differences in psychological distress, mindfulness, and coping strategies (adaptive vs. maladaptive) in university students (N = 122) with high and low levels of resilience. The results of a one-way MANOVA were consistent with hypotheses, revealing higher resilience scores were associated with greater mindfulness, higher adaptive coping scores, lower maladaptive coping, and reduced psychological distress. Students in the low resilience group were also found to have significantly lower levels of mindfulness, higher levels of psychological distress, reduced use of adaptive coping, and greater use of maladaptive coping, when compared to students with high resilience levels. Overall, findings of the current study are consistent with previous research and highlight the potential benefit of mindfulness-based coping interventions to foster resilience in university students

Submillimeter, millimeter, and microwave spectral line catalogue

A computer accessible catalogue of submillimeter, millimeter, and microwave spectral lines in the frequency range between O and 3000 GHz (such as; wavelengths longer than 100 m) is discussed. The catalogue was used as a planning guide and as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue was constructed by using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances

Submillimeter, millimeter, and microwave spectral line catalogue

This report describes a computer accessible catalogue of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10000 GHz (i.e., wavelengths longer than 30 micrometers). The catalogue can be used as a planning guide or as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue has been constructed using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances. Future versions of this catalogue will add more atoms and molecules and update the present listings (151 species) as new data appear. The catalogue is available from the authors as a magnetic tape recorded in card images and as a set of microfiche records

Submillimeter, millimeter, and microwave spectral line catalogue

A computer accessible catalogue of submillimeter, millimeter and microwave spectral lines in the frequency range between 0 and 3000 GHZ (i.e., wavelengths longer than 100 mu m) is presented which can be used a planning guide or as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue was constructed by using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances. Future versions of this catalogue will add more atoms and molecules and update the present listings (133 species) as new data appear. The catalogue is available as a magnetic tape recorded in card images and as a set of microfiche records

Half metallic digital ferromagnetic heterostructure composed of a δ\delta-doped layer of Mn in Si

We propose and investigate the properties of a digital ferromagnetic heterostructure (DFH) consisting of a $\delta$-doped layer of Mn in Si, using \textit{ab initio} electronic-structure methods. We find that (i) ferromagnetic order of the Mn layer is energetically favorable relative to antiferromagnetic, and (ii) the heterostructure is a two-dimensional half metallic system. The metallic behavior is contributed by three majority-spin bands originating from hybridized Mn-$d$ and nearest-neighbor Si-$p$ states, and the corresponding carriers are responsible for the ferromagnetic order in the Mn layer. The minority-spin channel has a calculated semiconducting gap of 0.25 eV. Analysis of the total and partial densities of states, band structure, Fermi surfaces and associated charge density reveals the marked two-dimensional nature of the half metallicity. The band lineup is found to be favorable for retaining the half metal character to near the Curie temperature ($T_{C}$). Being Si based and possibly having a high $T_{C}$ as suggested by an experiment on dilutely doped Mn in Si, the heterostructure may be of special interest for integration into mature Si technologies for spintronic applications.Comment: 4 pages, 4 figures, Revised version, to appear in Phys. Rev. Let

Studies on exploiting semiochemicals for pest management in organic farming systems OF0188

This study addresses the extent to which pest management systems can exploit semiochemicals (defined below) in ways acceptable to organic farming, and determines where the science base needs to be expanded to accommodate specific problems arising in an increasing organic farming sector. It considers whether current knowledge of semiochemical release from particular crop plants, herbs and wild plant species could be investigated further in relation to organic farming practice and identifies how strategies of multiple cropping, that exploit known semiochemical interactions, could be applied to key pest problems in organic production. Where such exploitation is not feasible, other strategies using semiochemicals including traps, extracts of natural products and nature-identical synthetic products are considered. Finally, general and specific directions in which research and development could facilitate greater penetration of the use of semiochemicals in crop protection for organic farming are identified. Semiochemicals are natural products that, by acting as signals, regulate interactions between organisms e.g. plants and insects. Once the semiochemical interactions between a pest and its host plant have been elucidated they can be exploited to regulate the pest population, providing an alternative control strategy to conventional toxicants. The choice of approach by which the semiochemicals are deployed relates to three options, i.e. from a natural plant source, from an extract or as a nature identical synthetic product. However, even where the most natural situations of mixed cropping are used, the scientific basis of the interaction must be established for robustness and sustainability of the approach. A complete understanding of the process allows a risk assessment to be made of any problems that might ensue when exploiting natural systems in different configurations from those encountered naturally. A major approach to using semiochemical based pest control is to exploit ways of repelling pests from crop plants and attracting them towards trap plantations. Deploying semiochemicals generated naturally by plants is consistent with organic farming practice, where a range of mixed cropping techniques are employed already, which ‘unconsciously’ utilise semiochemical effects. Thus, the acceptance and use of systems exploiting aspects of semiochemical deployment demonstrate an emerging role in organic farming practices. However, as emphasised before, a comprehensive knowledge of the semiochemical interactions that underpin these techniques is vital if they are to be exploited fully. Other pest control approaches compatible with organic farming, such as encouragement of beneficial species and the use of reflective surfaces in mulches, may not involve semiochemical effects, but could be exploited more beneficially by integration with semiochemical practices. Semiochemicals generated naturally by plants can be used to influence beneficial organisms as well as invertebrate pests. For example, plant defence chemicals, induced by pest or pathogen infestation, can affect the behaviour of pests and their natural enemies. Semiochemicals can be employed to maximise the impact of parasitic organisms that attack pest populations, for example in the management of refugia for maintaining and increasing populations of these beneficial organisms. In addition, the approach can be applied against other organisms antagonistic to agriculture besides invertebrate pests, for example in weed control, where signals interfering with weed germination can be exploited. Extracts of natural products provide semiochemicals in a form that is familiar and acceptable to organic farming practice, where plant extracts are already used as toxicants or as semiochemical antifeedants and repellents. However, often the scientific basis for use of these materials is limited, and therefore, exploitation is also limited and can be unreliable. By understanding the composition and the mechanism of activity of semiochemicals, natural product extracts can be improved by selection of the best sources of natural materials and appropriate processes of extraction and formulation. Many natural products, particularly pheromones (semiochemicals acting between members of the same species), can be synthesised as nature-identical and the synthetic forms are often indistinguishable from the natural form. Synthesis can be expensive, but where possible, starting materials should be obtained from natural renewable resources. Nature-identical synthetic pheromones are used widely in parts of the world, either deployed in traps for monitoring, mass trapping and lure and kill strategies or for direct pest control approaches such as mating disruption. In addition, manipulation of beneficial species with pheromones is being investigated and synthetic food-related attractants and oviposition attractants have also been developed for pests where pheromones are not available. Already some nature-identical synthetic semiochemicals have been accepted as compatible with organic farming practice. The registration of many sex and aggregation pheromones has been possible because they are nature-identical and are deployed away from the crop or on crop areas that are not consumed. In most cases, semiochemicals, deployed alone, are not sufficiently robust to control pest populations directly. They are most effective when incorporated into strategies, such as the ‘push-pull’ strategy, that are integrated with other forms of pest control, e.g. pathogens, parasitoids and predators, mechanical barriers and resistant plant varieties. The integration of semiochemical approaches with other methods of pest population reduction will help prevent the development of pest resistance to the overall strategy. Since the integrated strategy comprises a number of components that affect different aspects of pest behaviour and development each component can be relatively ineffective when compared to conventional pesticides. However, this has the advantage of not selecting efficiently for resistance to any component of the strategy and thus contributes to the sustainability of the approach. Recommendations 1) Develop a priority list of specific and general problems in organic production to be targeted by semiochemical methodologies in addition to known problems such as in carrot and lettuce production, aphids on a range of vegetable crops and for fruit pests. 2) Develop semiochemical based control methods suitable for 1) and for the targets already known. 3) Provide scientific input, where lacking, for 1 and 2. 4) Encourage greater diversification in organic cropping systems, including agroforestry, so as to exploit current knowledge of semiochemical based control and to pave the way for new interventions as the science develops. 5) Consider semiochemical attributes of non-crop plant inputs including mulches, weeds and multifunctional beneficial plants and the roles that they might play in organic systems. 6) Initiate organic plant breeding programmes, specifically to exploit natural semiochemical release where understood, for crop and companion plants