Magnetic properties of the spinel-type Cd1−xCoxCr2O4 (0 ≤ x ≤ 1.0) nanocrystals are systematically studied. Complementary results of the inductively coupled plasma optical emission spectroscopy (ICP-OES) and the dispersive X-ray spectroscopy (EDX) indicate cations redistribution with increased Cr concentration from the nanoparticle core to the surface. Powder X-ray diffraction (XRD) reveals an obtained single spinel phase of average crystallite size of 7–10 nm that is in consistence with TEM particle size. The lattice constant exhibits a general decrease by incorporating the smaller Co atoms, however its behavior violates Vegard’s law. An observed kink anomaly in the lattice constant behavior at x ~ 0.4 is attributed to the cations redistribution and further preferred site occupations. Static magnetization and AC susceptibility measurements reveal competitive magnetic phases in the solid solution nanocrystals. A superparamagnetic state of the noninteracting and single domain CdCr2O4 nanoparticles expands first to higher blocking temperatures at x < 0.4 before it evolves to a core collinear ferrimagnetic (FIM) state with coexisting surface spin-glass freezing. The low-temperature core spiral spin orders survive in the FIM phase. A tentative magnetic phase diagram is presented and discussed in a frame of effects of the type and redistribution of cations as well as emergent uncompensated surface spins on the nearest and next nearest neighbor exchanges in chromite nanospinels.

Magnetic properties of the spinel-type Cd1−xCoxCr2O4 (0 ≤ x ≤ 1.0) nanocrystals are systematically studied. Complementary results of the inductively coupled plasma optical emission spectroscopy (ICP-OES) and the dispersive X-ray spectroscopy (EDX) indicate cations redistribution with increased Cr concentration from the nanoparticle core to the surface. Powder X-ray diffraction (XRD) reveals an obtained single spinel phase of average crystallite size of 7–10 nm that is in consistence with TEM particle size. The lattice constant exhibits a general decrease by incorporating the smaller Co atoms, however its behavior violates Vegard’s law. An observed kink anomaly in the lattice constant behavior at x ~ 0.4 is attributed to the cations redistribution and further preferred site occupations. Static magnetization and AC susceptibility measurements reveal competitive magnetic phases in the solid solution nanocrystals. A superparamagnetic state of the noninteracting and single domain CdCr2O4 nanoparticles expands first to higher blocking temperatures at x < 0.4 before it evolves to a core collinear ferrimagnetic (FIM) state with coexisting surface spin-glass freezing. The low-temperature core spiral spin orders survive in the FIM phase. A tentative magnetic phase diagram is presented and discussed in a frame of effects of the type and redistribution of cations as well as emergent uncompensated surface spins on the nearest and next nearest neighbor exchanges in chromite nanospinels.

Magnetic properties of the spinel-type Cd1−xCoxCr2O4 (0 ≤ x ≤ 1.0) nanocrystals are systematically studied. Complementary results of the inductively coupled plasma optical emission spectroscopy (ICP-OES) and the dispersive X-ray spectroscopy (EDX) indicate cations redistribution with increased Cr concentration from the nanoparticle core to the surface. Powder X-ray diffraction (XRD) reveals an obtained single spinel phase of average crystallite size of 7–10 nm that is in consistence with TEM particle size. The lattice constant exhibits a general decrease by incorporating the smaller Co atoms, however its behavior violates Vegard’s law. An observed kink anomaly in the lattice constant behavior at x ~ 0.4 is attributed to the cations redistribution and further preferred site occupations. Static magnetization and AC susceptibility measurements reveal competitive magnetic phases in the solid solution nanocrystals. A superparamagnetic state of the noninteracting and single domain CdCr2O4 nanoparticles expands first to higher blocking temperatures at x < 0.4 before it evolves to a core collinear ferrimagnetic (FIM) state with coexisting surface spin-glass freezing. The low-temperature core spiral spin orders survive in the FIM phase. A tentative magnetic phase diagram is presented and discussed in a frame of effects of the type and redistribution of cations as well as emergent uncompensated surface spins on the nearest and next nearest neighbor exchanges in chromite nanospinels.

In this work, the synthesis of Ni1−x Mg x Fe2O4 (0 ≤ x ≤ 1.0) nanoparticles by a facile microwave-assisted combustion method is reported with detailed study of the structural and optical properties. By employing techniques of x-ray diffraction (XRD) with Rietveld refinement, transmission electron microscope (TEM, HRTEM, TEM-EDX), Fourier transform infrared spectroscopy (FTIR) and UV-Visible spectroscopy, the synthesized nanoparticles are characterized and introduced for further study of size-confined properties. Nanocrystals of a pure cubic spinel structured phase with average particle size of 20–40 nm were successfully synthesized in the whole range of x. In consistence with Vegard's law for a solid solution lattice, the lattice constant increases linearly with the substitution for Ni2+ with the relatively larger Mg2+ cations. The Rietveld analysis of the observed XRD patterns reveals an inversed spinel structure in NiFe2O4 nanoparticles with a decreased inversion factor by Mg-substitution. The results of UV-Visible absorbance indicate a wide energy gap of about 3.6 eV for NiFe2O4 nanoparticles thatmonotonically tuned towards a narrow band gap by Mg-doping.

Programmed cell death (PCD) is widespread during neurodevelopment, eliminating the surpluses of neuronal production. Using the Drosophila olfactory system, we examined the potential of cells fated to die to contribute to circuit evolution. Inhibition of PCD is sufficient to generate new cells that express neural markers and exhibit odor-evoked activity. These “undead” neurons express a subset of olfactory receptors that is enriched for relatively recent receptor duplicates and includes some normally found in different chemosensory organs and life stages. Moreover, undead neuron axons integrate into the olfactory circuitry in the brain, forming novel receptor/glomerular couplings. Comparison of homologous olfactory lineages across drosophilids reveals natural examples of fate change from death to a functional neuron. Last, we provide evidence that PCD contributes to evolutionary differences in carbon dioxide–sensing circuit formation in Drosophila and mosquitoes. These results reveal the remarkable potential of alterations in PCD patterning to evolve new neural pathways.

Insects use sex pheromones as a reproductive isolating mechanism to attract conspecifics and repel heterospecifics. Despite the profound knowledge of sex pheromones, little is known about the coevolutionary mechanisms and constraints on their production and detection. Using whole-genome sequences to infer the kinship among 99 drosophilids, we investigate how phylogenetic and chemical traits have interacted at a wide evolutionary timescale. Through a series of chemical syntheses and electrophysiological recordings, we identify 51 sex-specific compounds, many of which are detected via olfaction. Behavioral analyses reveal that many of the 42 male-specific compounds are transferred to the female during copulation and mediate female receptivity and/or male courtship inhibition. Measurement of phylogenetic signals demonstrates that sex pheromones and their cognate olfactory channels evolve rapidly and independently over evolutionary time to guarantee efficient intra-and inter-specific communication systems. Our results show how sexual isolation barriers between species can be reinforced by species-specific olfactory signals.

Phenotypic plasticity is the ability of individual genotypes to modify traits, such as physiological, morphological and behavioural characteristics, quickly in response to biotic and abiotic environmental variation (West-Eberhard, 1989; Agrawal, 2001a; Whitman and Agrawal, 2009). It can increase the fitness of individuals in their experienced environments (Lande, 2009), and may include changes in both behaviour and development within the lifetime of an organism. Such within-generation plasticity (WGP) has been observed in diverse taxa, and theoretical models of the phenomenon have been widely supported with empirical data (West-Eberhard, 1989; Lande, 2009).

Environmental variation experienced by a single genotype can induce phenotypic plasticity in various traits, such as behavioural, physiological and developmental characteristics. It can occur within the lifetime of an individual through within-generation phenotypic plasticity (WGP) or vertically across generations through transgenerational phenotypic plasticity (TGP). However, knowledge about TGP and the co-occurrence of WGP and TGP is still limited. In insect host-plant selection, the ability to alter phenotypic traits through WGP is well documented while the importance of TGP and the possible co-occurrence between the two is largely unknown. Host-plant selection of both larvae and adults of the polyphagous moth Spodoptera littoralis can be modified by previous experience through WGP. Thus, the aim of this study was to investigate if parental host-plant experience can influence host-plant choice behaviour and performance of S. littoralis offspring through TGP. For this, we tested effects of rearing parents on different host plants on the offspring’s first instar larval migration and host plant choice, larval development and adult oviposition. A transgenerational effect on larval development was found, with increased pupal weight on a matching host-plant diet to that of the parent, when larvae were reared on cotton (good larval host plant) while no such effect was found on maize (poor larval host plant). These findings indicate that TGP of S. littoralis progeny development traits may only occur under favourable conditions. Parental diet did not affect larval host plant choice or migration. Furthermore, no effect of parental diet was found on offspring oviposition behaviour, indicating that adult female host-plant selection is governed by innate preference hierarchy and WGP, rather than TGP. Thus, parental diet may influence offspring performance but not behaviour, indicating that WGP is most important for host-plant selection behaviours in S. littoralis, but TGP can affect progeny development. If so, the importance of different types of plasticity may vary among traits of S. littoralis associated with host plant utilisation.

Many species use early life sensory experiences to guide phenotypic plasticity and facilitate decision making during later adult settlement in new habitats or location of suitable resources. However, only some of the available sensory information in the environment is relevant for future decision making and, in addition, it may only be informative during certain times during development. This means that sampling of environmental information that should be retained to adulthood could be limited to certain sensitive periods. In the polyphagous moth Spodoptera littoralis, recent studies have demonstrated that adult females exhibit an innate preference hierarchy for certain plants that can be modulated by olfactory experience during the larval stage. This olfactory-driven phenotypic plasticity requires that information about plant quality is transferred over the full metamorphosis. However, the timing of information acquisition that affects adult behaviour and whether there is a sensitive period for the sensory experience inducing host plant preferences are not known. In this study, we tested whether experience used by adult females during host plant choice was acquired during early or later larval stages and whether adult females can retain larval experience from only one or from sequential feeding events on different plants. We found that only plant feeding experience during the later larval stages induced a host plant preference shift in adult females. Furthermore, our experiments demonstrated that when given an artificial diet in the later larval stage, adult females relied on their innate plant preference hierarchy even if they had feeding experience from a host plant in the early stages. The existence of a sensitive period during late larval stages may be constrained not only by neural development or limitations, but also by ecological factors affecting when the larval experience is most reliable for adult decisions.

The effect of intraperitoneal injection of growth hormone on hind limb regeneration was studied in two metamorphic stages of tadpoles of the Egyptian toad, Bufo regularis Reuss, after amputation at the mid shank level. Growth hormone enhanced limb regeneration in stage 56, where 77.8% of the cases regenerated toes ranging from five to one compared with 72.33% in the control group. Also, the differential effect of growth hormone on the number of toes was obvious in the treated animals, where 4.4% and 57.8% of the cases regenerated five and four toes respectively compared with 2.13% and 40.4% in the control group. In the metamorphic stage (stage 58), the effect of growth hormone was also obvious, where 75% of the treated cases restored part of the foot compared with 55.7% of the cases in the control group. Histological observations of the treated limbs revealed thick epithelial covering and complete skin faster than that of the control animals. Considerable amounts of cartilage were a histological characteristic of the treated limbs. It may be suggested that the limited enhancing effect of growth hormone on limb regeneration may be due to its acceleration of wound healing and shortening the period during which regeneration-stimulating factors pass from the epidermis to the underlying stump tissues.