Mannas, unique products of a dynamic insect-plant interaction: Biodiversity, conservation and ethnopharmacological considerations.

Biodiversity keeping increases the flexibility, interaction and adaptation of different ecosystems with the environment which benefits all organisms, including humans. This diversity can be maintained through different paths including co-evolution between insects and plants. One of these unique interactions leads to the production of "Mannas" in Iran, which have biological and ethno-medicinal importance. Considering the crises of biodiversity and the rapid extinction of species, in this research, we aimed to review the latest scientific findings about mannas and their biological, medicinal and bio perspective considerations. Until August 2023, all English publications in Web of Science, Science Direct, PubMed, Google Scholar and Scopus, as well as Persian databases such as Magiran, Iranmedex, Medlib, SID were surveyed using various search terms such as manna, angabin, sweet secretions and plant-insect interference. Articles that studied manna production from plants or provided a comprehensive description of host plants and manna producing insects were included in the study. In total, out of more than 180 reviewed articles, 113 articles met the inclusion criteria and 7 known mannas (Bidkhesht, Gaz-e-Alafi, Gaz-e-Khansar, Gaz-e-Shahdad, Shirkhesht, Shekartigal, and Taranjebin) have been explained here. This review deals with different aspects of special interactions between insects and plants that lead to the production of manna and presents different uses of manna from medicinal, ethnobotanical, health, conservation and bio perspective points of view. In addition, the changes in the population of manna-breeding insects and host plants are taken into consideration and influencing factors including loss of their growth conditions and climatic conditions, animal breeding in the region, inappropriate exploitation methods and host preference phenomenon which increase the risk of destruction of these natural products have been given. These mannas cannot be produced in any way, and maintaining their production conditions requires environmental care and providing necessary training.

X-ray diffraction reveals the amount of strain and homogeneity of extremely bent single nanowires.

Core-shell nanowires (NWs) with asymmetric shells allow for strain engineering of NW properties because of the bending resulting from the lattice mismatch between core and shell material. The bending of NWs can be readily observed by electron microscopy. Using X-ray diffraction analysis with a micro- and nano-focused beam, the bending radii found by the microscopic investigations are confirmed and the strain in the NW core is analyzed. For that purpose, a kinematical diffraction theory for highly bent crystals is developed. The homogeneity of the bending and strain is studied along the growth axis of the NWs, and it is found that the lower parts, i.e. close to the substrate/wire interface, are bent less than the parts further up. Extreme bending radii down to ∼3 µm resulting in strain variation of ∼2.5% in the NW core are found.

Beam damage of single semiconductor nanowires during X-ray nanobeam diffraction experiments.

Nanoprobe X-ray diffraction (nXRD) using focused synchrotron radiation is a powerful technique to study the structural properties of individual semiconductor nanowires. However, when performing the experiment under ambient conditions, the required high X-ray dose and prolonged exposure times can lead to radiation damage. To unveil the origin of radiation damage, a comparison is made of nXRD experiments carried out on individual semiconductor nanowires in their as-grown geometry both under ambient conditions and under He atmosphere at the microfocus station of the P08 beamline at the third-generation source PETRA III. Using an incident X-ray beam energy of 9 keV and photon flux of 1010 s-1, the axial lattice parameter and tilt of individual GaAs/In0.2Ga0.8As/GaAs core-shell nanowires were monitored by continuously recording reciprocal-space maps of the 111 Bragg reflection at a fixed spatial position over several hours. In addition, the emission properties of the (In,Ga)As quantum well, the atomic composition of the exposed nanowires and the nanowire morphology were studied by cathodoluminescence spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy, respectively, both prior to and after nXRD exposure. Nanowires exposed under ambient conditions show severe optical and morphological damage, which was reduced for nanowires exposed under He atmosphere. The observed damage can be largely attributed to an oxidation process from X-ray-induced ozone reactions in air. Due to the lower heat-transfer coefficient compared with GaAs, this oxide shell limits the heat transfer through the nanowire side facets, which is considered as the main channel of heat dissipation for nanowires in the as-grown geometry.

Characterization of individual stacking faults in a wurtzite GaAs nanowire by nanobeam X-ray diffraction.

Coherent X-ray diffraction was used to measure the type, quantity and the relative distances between stacking faults along the growth direction of two individual wurtzite GaAs nanowires grown by metalorganic vapour epitaxy. The presented approach is based on the general property of the Patterson function, which is the autocorrelation of the electron density as well as the Fourier transformation of the diffracted intensity distribution of an object. Partial Patterson functions were extracted from the diffracted intensity measured along the [000\bar{1}] direction in the vicinity of the wurtzite 00\bar{1}\bar{5} Bragg peak. The maxima of the Patterson function encode both the distances between the fault planes and the type of the fault planes with the sensitivity of a single atomic bilayer. The positions of the fault planes are deduced from the positions and shapes of the maxima of the Patterson function and they are in excellent agreement with the positions found with transmission electron microscopy of the same nanowire.

Threefold rotational symmetry in hexagonally shaped core-shell (In,Ga)As/GaAs nanowires revealed by coherent X-ray diffraction imaging.

Coherent X-ray diffraction imaging at symmetric hhh Bragg reflections was used to resolve the structure of GaAs/In0.15Ga0.85As/GaAs core-shell-shell nanowires grown on a silicon (111) substrate. Diffraction amplitudes in the vicinity of GaAs 111 and GaAs 333 reflections were used to reconstruct the lost phase information. It is demonstrated that the structure of the core-shell-shell nanowire can be identified by means of phase contrast. Interestingly, it is found that both scattered intensity in the (111) plane and the reconstructed scattering phase show an additional threefold symmetry superimposed with the shape function of the investigated hexagonal nanowires. In order to find the origin of this threefold symmetry, elasticity calculations were performed using the finite element method and subsequent kinematic diffraction simulations. These suggest that a non-hexagonal (In,Ga)As shell covering the hexagonal GaAs core might be responsible for the observation.