Biosystematic studies on the Muellerianella complex (Delphacidae Homoptera Auchenorrhyncha)

The genus Muellerianella comprises the species: M. farmairei, M. brevipennis, M. relicta and one pseudogamous all-female biotype M. fairmairei (3n). The bisexual species M. fairmairei and M. brevipennis as well as the unisexual M. fairmairei (3n) were investigated from a biosystematic point of view. The males of the two bisexual species are morphologically distinct but their females, the female hybrids of both way-crossings between the two bisexual species and the unisexual biotype are morphologically indistinguishable.The bisexual species M. fairmairei and M. brevipennis are diploid (2n = 28) and their sex determination system is XY. F1 hybrids also have 28 chromosomes. The pseudogamous unisexual biotype is triploid (3n = 41) reproducing apomictically, but it requires sperm derived from the males of the two bisexual species to initiate embryogenesis (pseudogamy).The host plants of the Muellerianella complex are Holcuslanatus or H.mollis for the bisexual and unisexual M. fairmairei, and Deschampsia caespitosa for M. brevipennis.The distributions of the two species and their host plants overlap widely in West and Central Europe. M. fairmairei and its host plant are distributed more to the south, while M. brevipennis and its host extend more to the north. There is evidence that the unisexual M. fairmairei (3n) occurs in the overlapping area of the two bisexual species, but is absent from the peripheral areas where one of the other species is also absent.In the area of Leersum-Langbroek (prov. of Utrecht) in Holland both species are common, and their respective host plants grow in reasonable numbers. In a few localities where the two hosts are closely intermixed both delphacid species occur syntopically.Samples of the two species were taken bij the sweep-net and suction methods. M. fairmairei is more frequent in wet biotopes of noncultivated meadows in West Europe. M. brevipennis is more frequent in the north of Europe and is a stenotopic species typical of fresh biotopes of wooded areas.In Northern Europe both species are univoltine while in West and Central Europe M. fairmairei has two distinct generations in contrast to M. brevipennis which has an incomplete second generation. However, there is no important seasonal isolation between the two species. In Southern Europe M. fairmairei is probably polyvoltine.Populations of M. fairmairei from regions where M. brevipennis does not occur (S. Greece, S. France?, Ireland) have a sex ratio of 1 : 1, while populations occurring sympatrically with M. brevipennis (England, France, Holland) have a high proportion of females, comprising a mixture of diploid and triploid individuals. In Holland M. brevipennis has a sex ratio of1 : 1, while populations of this species in Finland have a high proportion of females.Both diploid species maintained a 1:1 sex ratio in the laboratory rearings. Crossings between triploid females and males of M. fairmairei resulted in absolute all-female triploid progenies. Diploid and triploid females of M. fairmairei coexist in Holland. In one biotope (in Leersum), the proportion of the two female biotypes of M.fairmairei was 1:1, while in others triploid females were more numerous than the diploid ones. It is not clear, whether both female populations of M. fairmairei occupy exactly the same ecological niche.Regarding the wing form of the two bisexual species and the unisexual biotope, long photoperiod (L:D = 18:6) favors the development of the long wings, while short photoperiod (L:D = 10:14) completely suppresses it. Under long photoperiod the macropterous form of M. brevipennis was more common than that of M. fairmairei. Under long photoperiod, when the larval density was increased M. fairmairei (2n) had proportionately more macropterous adults than M. fairmairei (3n).Summer and winter eggs of the two species were parasitized by Anagrus sp. However, eggs of the second generation were more frequently parasitized (up to 40%) that those of the first.The higher population densities of M. fairmairei than of M. brevipennis in the field were interpreted from laboratory observations by the fact that M. fairmairei has higher egg production than M. brevipennis. The triploid females of M. fairmairei are assumed to be more prolific than the diploid ones. Also, the rate of egg production of M. fairmairei was higher than that of M. brevipennis. Females of M. fairmairei mated once produced a few unfertile eggs at the end of their oviposition period, in contrast to M. brevipennis which always produced fertile eggs. Males of M. fairmairei appeared to have greater longevity than the females.During the first generation and in colonies under long photoperiod M. fairmairei oviposits in its food plant H. lanatus, while during the second generation and in colonies under short photoperiod in Juncus effusus. M. brevipennis was found to oviposit in the field only in its food plant, namely D. caespitosa, but in the laboratory it also oviposited in J. effusus. The egg-group size of both species depends upon the oviposition substrate.Embryonic development of both species is continuous during the first generation and in colonies under long photoperiod, but embryonic diapause (arrest of development before blastokinesis) takes place during the second generation and in laboratory rearings under short photoperiod. The intensity of diapause is higher in M. brevipennis as compared to M. fairmairei. Continuous rearings of the unisexual and bisexual M. fairmairei were possible under short photoperiod.The rate of larval development of both species under long photoperiod at 20- 25°C was approximately the same. Under short photoperiod the duration of the last instar larva of females is longer than that under long photoperiod. Temperature, humidity and crowding had an influence upon the rate of larval development.In laboratory experiments, development and reproduction of M. fairmairei occurred on several grass species, in contrast to M. brevipennis which appeared to be monophagous. Mature grasses were more suitable as food plants than seedlings.Some unmated females of M. fairmairei (2n) placed in cages containing H. lanatus and D. caespitosa, and males of M. brevipennis ultimately produced a few male and female hybrids. The reciprocal cross resulted in more female hybrids than males. Egg-fertility of these crosses was variable (0-100%) during the course of the oviposition period. Hybrid larvae can develop on both grass species, but they prefer D. caespitosa to H. lanatus. Males were sterile but females were often fertile and some of them crossed back with M. fairmairei produced a triploid pseudogamous biotype very similar to that collected in the field. The all-female progeny of the triploid M. fairmairei was greater when it was crossed with M. fairmairei males than with M. brevipennis males. Hybrids were obtained even when unmated females (2n + 3n) of both species together were caged with males of one species.In conformity with these results it is proposed that the two bisexual species should be called 'allomorphic-related species' instead of 'sibling species'. Allopatric speciation is considered as the most probable cause of divergence between both species. It is suggested that M. brevipennis originated from an isolated population of M. fairmairei during a period of glaciation and has survived on D. caespitosa.It is proposed to call the unisexual biotype M.2 fairmairei-brevipennis, following the nomenclatorial system of hybrids. In this context, it has been demonstrated that in insects hybridization may lead to unisexuality followed by polyploidy.<br/

Evaluation of the dynamic response of structures using auxetic-type base isolation

Base isolation is a widely-used method used to minimise the harmful effects of earthquakes on buildings. Unlike a fixed base building, a building with a base isolation system essentially decouples the superstructure from the substructure resting on the ground. Then, during earthquakes, the superstructure’s relative displacement is significantly reduced, minimising the structural damage. Auxetics, which are materials with a negative Poisson’s ratio, are known for possessing properties such as high energy absorption. Based on the energy absorbing capabilities of auxetic materials, it is proposed that incorporating them into base isolation structures would positively impact on the performance of the system. Therefore, the article aims to investigate the response of structures under seismic loading incorporating re-entrant hexagon layers into the base isolation system. This is assessed by defining and numerically testing the system using finite element analysis. The models developed for this study represent multi-storey structural steel frames combined with fixed base, conventional lead-rubber bearing and auxetic composite base isolation. Differences in the response obtained from the mentioned systems are highlighted. Results indicate that the auxetic base isolation may improve the dynamic response of structures, although a unique performance is not recorded

The active site residue Valine 867 in human telomerase reverse transcriptase influences nucleotide incorporation and fidelity

Human telomerase reverse transcriptase (hTERT), the catalytic subunit of human telomerase, contains conserved motifs common to retroviral reverse transcriptases and telomerases. Within the C motif of hTERT is the Leu866-Val867-Asp868-Asp869 tetrapeptide that includes a catalytically essential aspartate dyad. Site-directed mutagenesis of Tyr183 and Met184 residues in HIV-1 RT, residues analogous to Leu866 and Val867, revealed that they are key determinants of nucleotide binding, processivity and fidelity. In this study, we show that substitutions at Val867 lead to significant changes in overall enzyme activity and telomere repeat extension rate, but have little effect on polymerase processivity. All Val867 substitutions examined (Ala, Met, Thr) led to reduced repeat extension rates, ranging from ∼20 to 50% of the wild-type rate. Reconstitution of V867M hTERT and telomerase RNAs (TRs) with mutated template sequences revealed the effect on extension rate was associated with a template copying defect specific to template A residues. Furthermore, the Val867 hTERT mutants also displayed increased nucleotide incorporation fidelity, implicating Val867 as a determinant of telomerase fidelity. These findings suggest that by evolving to have a valine at position 867, the wild-type hTERT protein may have partially compromised polymerase fidelity for optimal and rapid repeat synthesis

All hands on deck: An innovative approach to sustained and sustainable conservation funding for endangered plants and ecosystems

The Red List Project (TRLP) was founded in 2018 as an NGO [501(c)(3)], dedicated to preventing the extinction of the world's most endangered plant species and to protecting biodiversity hotspots. This approach is highlighted by an ongoing partner ship between TRLP, independent fragrance house Baruti Perfumes and the University of Palermo, to prevent the extinction of the Viola ucriana Erben and Raimondo, critically endangered. This violet is restricted to the slopes of Mt Pizzuta in the Serre della Pizzuta Nature Reserve in Sicily (Italy), between 950 and 1300 m s.l.m., where it grows in xeric prairies and is threatened by factors partly related to human disturbance (e.g., fires, grazing, etc.)

Finite element analysis of fire resistant reinforcement on end-plate steel connections

In this paper the effect of fire resistant coatings on the mechanical behaviour of steel joints is studied using the finite element method. The proposed finite element model is an extension of a previous one developed for the study of the same connection in elevated temperatures, without fire reinforcement. In particular, the construction used consists of an end – plate steel connection which is covered with panels of lightweight concrete and gypsum board. The behaviour of those two fire resistant materials has been simulated in elevating mechanical and thermal conditions separately and simultaneously. Through this process it is examined the strength of the materials and of the overall construction. Specifically, the action of fire on the strength of the structure may result in an early collapse. In addition, the behaviour of the structure in the connection area and the opening of the interface is investigated

Mediterranean species of the spittlebug genus "Philaenus" : modes of chromosome evolution

The evolution of karyotypes and sex determination system of Philaenus Stål (Auchenorrhyncha: Aphrophoridae) species is studied here in detail. The most plausible scenario of chromosomal rearrangements accompanying phylogenetic differentiation in Philaenus is advanced. It is postulated that the ancestral karyotype of Philaenus was 2n = 24 + X0. Karyotype changes occurred several times independently in the genus. The karyotype of 2n = 22 + X0 (P. spumarius and P. tesselatus) originated from 2n = 24 + X0 by fusion between two autosomal pairs. The neo—XY system (P. arslani, P. loukasi, P. signatus, P. maghresignus, and P. tarifa) also originated from the 24 + X0 karyotype by means of independent fusions between autosomes and the original X chromosome. The neo—X(1)X(2)Y system (P. italosignus) evolved from the 2n = 22 + neo—XY karyotype by an additional fusion between the Y chromosome and one more autosomal pair. The neo—X(n)Y system of P. italosignus is the first reported case of an evolutionarily fixed multiple sex chromosome system in Auchenorrhyncha

Failure behaviour of a fire protected steel element

In the present article the failure behaviour of a steel, beam type element supported against fire by protection boards, is studied. Three dimensional, coupled temperature - displacement, non-linear finite element analysis models have been developed to simulate the unprotected and protected structure. A simple modelling approach is proposed for the investigation of the influence of the gradual failure of fire protection at elevated temperatures, on the structural performance of the system, under thermal and mechanical loads. Yielding of steel is depicted and force displacement diagrams are used to evaluate the ultimate behaviour of the unprotected and protected models. It is shown that for the protected structure, yielding is less severe and the time period up to maximum strength is significantly longer. Eventually, is depicted how failure of the fire protection leads to a gradual reduction of the response, in fire condition

Failure behaviour of a fire protected steel element

In the present article the failure behaviour of a steel, beam type element supported against fire by protection boards, is studied. Three – dimensional, coupled temperature - displacement, non-linear finite element analysis models have been developed to simulate the unprotected and protected structure. A simple modelling approach is proposed for the investigation of the influence of the gradual failure of fire protection at elevated temperatures, on the structural performance of the system, under thermal and mechanical loads. Yielding of steel is depicted and force – displacement diagrams are used to evaluate the ultimate behaviour of the unprotected and protected models. It is shown that for the protected structure, yielding is less severe and the time period up to maximum strength is significantly longer. Eventually, is depicted how failure of the fire protection leads to a gradual reduction of the response, in fire conditions

Multi-objective optimization for maximum fundamental frequency and minimum cost of hybrid graphene/fibre-reinforced nanocomposite laminates

The present article proposes a multi-objective optimization study aiming at the optimal cost-effective design of nano-reinforced laminates. To maximize the fundamental frequency and minimize the cost, a hybrid laminate is studied, introducing both conventional fibres and graphene nanoplatelets reinforcement. A multi-objective genetic algorithm optimization is adopted to provide the optimal natural frequency and cost for the laminate. Optimization is implemented using the Non-dominated Sorting Genetic Algorithm II (NSGA-II), which converges to near-optimal solutions for all scenarios tested. The vibration problem is solved using the finite element method and the first-order shear deformation theory. Effective material properties are derived using micromechanical equations. Different optimization problems are solved using one to four types of design variables, including graphene and fibre distribution along the thickness, layer thickness, and fibre angles. Results indicate that increasing the graphene nanoplatelets content and keeping the minimum fibre content leads to cost-effective design. A drastic increase in the fundamental frequency and decrease in the cost is obtained for the hybrid graphene/fibre-reinforced laminate compared to conventional fibre-reinforced composites

Impact of partially damaged passive protection on the fire response of bolted steel connections using finite element analysis

This article aims to quantify the impact of a potential failure of passive fire protection on the ultimate response of a top and seat steel connection with double web angles. A numerical, finite element analysis scheme is proposed considering the real, semi-rigid behaviour of the connection, using unilateral contact-friction laws between the interfaces of the beam, the column, and the steel angles. The model has been validated by previous experimental research at ambient temperatures. Scenarios of unprotected connections, undamaged and partially damaged fire protections are numerically tested. A change in the failure mode and a reduction of the strength equal to 28% for standard fire and 35% for hydrocarbon fire arise for the model with the damaged protection. In this case, maximum temperatures locally at the beam reach the ones of the unprotected connection (900 °C), which is more than 800 °C higher than the connection with undamaged protection. Significant temperature increases of more than 288 °C and 406 °C for standard and hydrocarbon fires also arise on the top angle, compared to the model with undamaged fire protection