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Dry heat is proposed as a non-chemical postharvest disinfestation treatment for export persimmons (Diospyros kaki L.). A fruit surface temperature of 47°C at 55–60% RH for 15 min is recommended to effect 100% mortality of thrips, mealybugs, and leafrollers. On persimmon fruit these are all surface dwelling pests. Fruit tolerance trials showed that this fruit surface temperature/time exposure was not detrimental to persimmon fruit firmness, soluble solids concentration, and appearance; and did not reduce shelf life. A commercial scale confirmatory trial is planned.

The effectiveness of 2 traps for Queensland fruit fly, Bactrocera tryoni was compared for 1 year amongst relatively low populations at Applethorpe-Stanthorpe in southeast Queensland. The Lynfield trap which is an inexpensive, non-sticky, pot-type trap was significantly more effective than the Jackson trap and was at least as reliable in the detection of fruit fly populations. Use of Lynfield traps in quarantine surveillance programs should allow for a greater trap density and a more sensitive detection system to be established without vastly increased operational costs.

At the moment scanning transmission electron microscopy (stem) instruments are not competetive with conventionaltem instruments for high resolution bright field imaging. For studies of the structure and defects of crystalline materials, their special virtues lie in the application of dark field imaging modes combined with observations of microdiffraction patterns from regions of diameter comparable with the microscope resolution limit (currently about 5 A). They also offer capabilities for microanalysis by use of energy dispersive x-ray spectroscopy (eds) or electron energy loss spectroscopy (els). In principle the spatial resolution of these microanalysis methods is comparable to that of the imaging modes but in practice it is limited by poor signal-to-noise ratios or by the nonlocalized nature of the inelastic scattering process. The capabilities for microdiffraction are illustrated by sequences of diffraction patterns obtained as the incident beam is moved within the unit cell of a crystal of large (20 A) periodicity. Applications of more immediate practical significance include diffraction studies of small crystallites of gold 20 to 50 A in diameter and of the near-amorphous, thin oxide layers formed on chromium and iron films at room temperature. Microdiffraction, combined with reflection electron microscopy andels analysis, provides a powerful new approach to the study of the surface structure of crystals, including bulk samples, and the investigation of surface reactions. In particular, if a beam of small diameter (10–20 A) is made to run along the face of a small crystal, the diffraction pattern andels curves are very sensitive to the form of the potential distribution at the surface and the excitations of the surface states of the crystal.

The electron microscope image intensity of a thin crystal is described as a time average of the image of a crystal perturbed by time-dependent fluctuations corresponding to thermal motion of the atoms or low-energy electronic excitations. For very thin crystals the phase-object approximation indicates that images having atomic resolution may be obtained from the inelastically scattered electrons. It is shown that the use of suitable approximations allows estimates to be made of the contribution of the inelastically scattered electrons to the high-resolution images of thicker crystals. The resolution of images formed by inelastically scattered electrons is not affected by the non-localization of the inelastic scattering process.

Claims that single heavy atoms have been seen in high resolution electron microscope images have become commonplace in recent years. The accumulated experimental experience and theoretical contrast calculations suggest that in many cases these claims are fully justified. The performance of modern electron microscopes, when used at the limits of their capabilities, is such that one can begin to contemplate the use of "atomic resolution electron microscopy" as a fun damentally new and enor­ mously powerful method for the study of the structure of matter in terms of the detailed arrangements of the constituent atoms. In this review we report the initial applications of this new level of electron micros­ copy to a range of topics of particular relevance for physical chemistry; namely, the atom configurations on the surfaces of solids and in the defects within thin crystals. In some cases inf ormation at the level of atomic resolution has already been achieved. In many cases enough has been accomplished to suggest that a flood of information on atomic arrangements will follow from the use of the next generation of high resolution microscopes now under construction or being planned. In other cases we must rely on extrapolation beyond our present technical capabilities for initial results that appear feasible on the basis of theoretical analyses. It is our purpose to call attention to the range of exciting possibilities for new developments in this area in order to stimulate interest and support for the efforts being made.

Dynamical diffraction effects of diffuse scattering due to point defects in crystals and the associated imaging are studied in relation to imaging of the short-range order in disordered alloys through theoretical formulations and computer image simulations. Simulations of gold crystals including one point defect without strain show that the image contrast is localized in atomic size and relatively insensitive to the defect depth when the total thickness is fixed. The contrast from a small number of defects in an atomic column can be simply related to the number of defects by a nonlinear expression. An approximate imaging theory for short-range order in disordered binary alloys is discussed. The present study shows that the important parameters for observations of defective crystals are total thickness and microscope defocus, but not the defect depth. With controlled values of these parameters and sample conditions, the images of disordered binary alloys can be interpreted semi-quantitatively.

Since the previous Annual Review article written on High Resolution Electron Microscopy (HREM), nine years ago (l), considerable changes have occurred. The resolution achieved has improved considerably. New techniques have been added. For some of the techniques, previously omit­ ted as not giving sufficiently "high" resolution, improvements have clearly placed them in the high resolution category. Some of the areas of appli­ cation remain the same. Even more effort is concentrated in the surfaces of crystals and the defects in thin crystal films as the methods that can be applied to these studies have become much more powerful . Other areas of application have come into prominence as the improved resolution and techniques have greatly expanded the range of information that can be derivcd, as is the case for the small metal particles or clusters, of importance for catalysis, and the interfaces between phases, which are highly significant in present-day semiconductor research. To some extent, these extensions of the power of the electron microscopy techniques have fol lowed from the improvements in the standard com­ mercial instruments. Other extensions, which may be even more significant for the future of solid state science, derive from the few experimental instruments with which further possibilities have been demonstrated. Increasingly, television (TV) systems with image intensifiers are being applied with image recording on video-tape or in digital form in image frame stores. With such systems the time dependence of dynamic processes may be studied with near-atomic resolution . Microscopes having ultra­ high vacuum environments for the specimen during observation and dur­ ing preparation are being produced to allow the study of clean surfaces with high spatial resolution . With such instruments i t becomes feasible to

The scattering of electrons by three-dimensional potential fields, and, in particular, the potential fields associated with a crystal lattice, is considered in terms of the new approach to physical optics proposed by Cowley & Moodie.

Around Auckland, New Zealand, the gorse seed weevil (Apion ulicis Forster) has retained 1 generation per year, as in the United Kingdom, its country of origin. Gorse (Ulex europaeus) bushes produce 2 crops of seeds annually, but only seeds of the second crop (July—December) are attacked by the weevil. During this time more seeds are found per pod than during the first crop (February—May). In this study weevil attack effectively reduced the viable seeds from around 3 per pod to 1 per 4 pods. However, only a relatively small proportion of seed pods were attacked by A. ulicis.

Application of the novel techniques developed in this laboratory and especially those resulting from our modifications of the scanning transmission electron microscope, have allowed considerable progress with studies on the oxidation of chromium and chromium-iron alloys and on the surface structure of magnesium oxide and related materials. Microdiffraction from regions 10 to 20A in diameter has allowed clarification of the nature and epitaxial relationships of the very thin oxide layers formed when chromium films are heated. The new observations include the existence of a uniform thin layer of a previously undetected spinel-structure phase. Deductions have been made on the factors influencing growth of the oxide layers. Also it has been shown by use of STEM imaging, microdiffraction and ELS that the oxide film formed on thin chromium films in air at room temperature is amorphous and about 5A thick. The development of techniques for the study of surfaces by reflection diffraction imaging have allowed the visualization of growth steps only 2 to 5A high on the surfaces of MgO smoke particles and a combination of ELS, imaging and diffraction methods has permitted the detection of excited surface states of the first few atomic layers on crystal surfaces. The observation of a new type of interference fringe in defocussed images of small crystals promises to provide extremely sensitive methods for study of the variations of potential at crystal surface. Remodelling of the medium-energy electron diffraction and microscopy system should allow greatly improved performance for surface studies.

The possibility of obtaining electron diffraction patterns from very small specimen regions combined with high resolution imaging by use of scanning transmission electron microscopy (STEM) allows the detailed study of small nuclei of reaction products or of crystal defects. The capabilities of this method have been extended by the design and construction of a TV system for the viewing and recording of microdiffraction patterns from our STEM instrument so that clear patterns can be obtained from regions as small as 10A in diameter. This system has been applied to the study of initial stages of oxidation of chromium films, revealing the presence of very small oxide nuclei and identifying these crystals as having a previously unsuspected spinel structure. The further stages of growth of oxides on chromium are being investigated. Initial results have also been obtained on the surface structure of oxides such as MgO. The extension of previous work on the diffraction from, and imaging of crystal surfaces by the use of medium-to-low energy electrons (15 to 1 keV) has allowed a much more complete understanding of the contrast-producing mechanisms. Application to the study of pyrolytic graphite surfaces has given a clear picture of the mosaic structure and defectmore » distribution and provided a basis for the more reliable and quantitative general use of these techniques in surface structure analysis.« less

Progress is reported in the evaluation and comparison of various electron optical techniques for the study of surface reactions on single-crystal materials. The principal reaction studied has been the oxidation of copper at temperatures of 400 to 800/sup 0/C in oxygen partial pressures of 10/sup -5/ torr and less using thin single crystal films of copper on solid substrates. This reaction has been followed from the initial formation of oxide nuclei (100A diameter) to the growth of oxide crystals several micrometers in diameter. New information has been provided on the mechanism of the growth of the oxide and on the diffusional processes in the surrounding copper. The techniques used have included scanning electron microscopy (including electron channelling observations), scanning reflection microscopy using diffracted beams at medium energies (a technique unique to our laboratory), medium energy (1 to 15 keV) electron diffraction, transmission electron microscopy, transmission electron diffraction, high energy reflection electron diffraction and high energy reflection electron microscopy. New methods have been developed for the preparation of thin single crystal films and bulk crystals suitable for use as specimens. Exploratory studies have been made on graphite single crystals and thin chromium films. Theoretical studies have revealed possible errors in themore » interpretation of diffraction patterns from small crystals on mono-crystalline supports and have shown the importance of multi-beam dynamical diffraction effects in reflection-diffraction imaging of mosaic single crystals.« less

IN a recent communication, Hashimoto and Watanabe1 report the observation of extra lines outside the geometric bounds of the electron microscope image of a crystal of copper phthalocyanine when the microscope is de-focused to obtain the Fourier image of order N = ½ (see Cowley and Moodie2). They state that “such lines are not explicable by the theory of Cowley and Moodie”.

GRAPHITIC oxide is the pale, non-conducting product formed in treating graphite in suspension with strong oxidizing reagents. The composition is not well defined but is usually given as approximately C4O(OH) for the most highly oxidized form. The structural information which can be obtained by X-ray methods is limited because the structure is heavily disordered. One strong ring in X-ray patterns indicates an inter-layer c-spacing of about 6.2 A for the dehydrated compound. Two or three weak lik bands may be interpreted to indicate a hexagonal structure of the layers with a spacing of 2.45 A. This and some chemical evidence have suggested that the layers are made up of puckered graphite-like sheets. The various proposals which have been made concerning the bonding of oxygen and OH groups are summarized in recent reviews by Hennig1 and Croft2.

IN recent years the techniques of X-ray diffraction structure analysis have been refined to such an extent that, with careful work, the positions of hydrogen atoms in a structure may be determined when each hydrogen atom is bound to a single atom. The detection of a hydrogen ion in a hydrogen bond, however, is a much more difficult task, since only a fraction of an electron can be considered as localized near the proton. This amount of ionization reduces the atomic scattering factor for X-rays. However, the atomic scattering factor for electrons is correspondingly increased since this is given by ɛ = (Z − ƒ)λ2/sin2θ, where Z is the atomic number, ƒ is the X-ray scattering factor, λ is the effective wave-length of the electron beam and θ is the Bragg angle. Hence, hydrogen ions in hydrogen bonds should be detected more readily in structure analyses based on electron diffraction data. Techniques for structure analysis using single-crystal electron diffraction patterns have been evolved and will be described elsewhere. They have been applied to the study of the structure of boric acid layers.

The diffraction of electrons is, in principle, a very sensitive probe of the relative atomic positions in ordered or disordered crystals. The full potential of electron diffraction and electron microscopy methods for the study of local atomic arrangements has not been realised because of the difficulties of conducting experiments under sufficiently well defined conditions and because of the complications introduced by the dynamical diffraction processes involved.

WHEN beryllia flakes, supported on thin carbon films to form electron microscope specimens, are strongly irradiated with an electron beam, they disintegrate and small crystals condense on the surrounding carbon film. Willis, Austerman and Dearborn1 reported that the condensed material gives electron diffraction ring patterns which they identify as being those of the high-temperature β-BeO phase examined by Smith, Cline and Frechette2. These latter authors suggest that the β-phase is cubic, a0 = 4.76 A, with a non-trivial structure. According to Austerman3, more recent work has suggested that the structure may be hexagonal or tetragonal.

THE distribution of plastic deformation in a cold-stretched mild steel bar has been studied by X-ray diffraction methods. Using the back-reflexion technique with cobalt radiation, two spotty rings were obtained by reflexion of the K α doublet from the (310) plane of iron. Plastic deformation in the specimen was indicated by a blurring of the spots of the diffraction patternas the individual crystals, which gave the reflexions, became distorted. An X-ray beam of about 1 mm. diameter was used to explore the distribution of the deformation.

THE decrease of manganous ion concentration which occurs when a manganous salt is shaken with manganese dioxide has been known for a long time. Being most marked with freshly precipitated oxides, it is not surprising it should first have been considered an adsorption. For some time this observation has found practical application in the removal of soluble manganese in water supplies1, while recently it has been shown of significance in the chemistry of the dry cell depolarizer2, and also in the oxidation-reduction cycle of manganese in the soil3,4.