Strategies for Controlled Placement of Nanoscale Building Blocks

The capability of placing individual nanoscale building blocks on exact substrate locations in a controlled manner is one of the key requirements to realize future electronic, optical, and magnetic devices and sensors that are composed of such blocks. This article reviews some important advances in the strategies for controlled placement of nanoscale building blocks. In particular, we will overview template assisted placement that utilizes physical, molecular, or electrostatic templates, DNA-programmed assembly, placement using dielectrophoresis, approaches for non-close-packed assembly of spherical particles, and recent development of focused placement schemes including electrostatic funneling, focused placement via molecular gradient patterns, electrodynamic focusing of charged aerosols, and others

Evidence for a Müllerian mimetic radiation in Asian pitvipers

Müllerian mimicry, in which toxic species gain mutual protection from shared warning signals, is poorly understood in vertebrates, reflecting a paucity of examples. Indirect evidence for mimicry is found if monophyletic species or clades show parallel geographic variation in warning patterns. Here, we evaluate a hypothesis of Müllerian mimicry for the pitvipers in Southeast Asia using a phylogeny derived from DNA sequences from four combined mitochondrial regions. Mantel matrix correlation tests show that conspicuous red colour pattern elements are significantly associated with sympatric and parapatric populations in four genera. To our knowledge, this represents the first evidence of a Müllerian mimetic radiation in vipers. The putative mimetic patterns are rarely found in females. This appears paradoxical in light of the Müllerian prediction of monomorphism, but may be explained by divergent selection pressures on the sexes, which have different behaviours. We suggest that biased predation on active males causes selection for protective warning coloration, whereas crypsis is favoured in relatively sedentary females

Effect of dislocations in relaxed MBE SiGe layers on the electrical behavior of Si/SiGe heterostructures

Defects in Si/SiGe heterostructures and electrical behavior thereof have been studied. Misfit dislocations were observed in the epitaxial layers using cross-sectional transmission electron microscopy. These defects cause anomalies in the electrical behavior. It has been shown that, in spite of anomalies, the electrical measurements provide useful and reliable information on the structures.Исследованы дефекты в гетероструктурах Si/SiGe и их электрические характеристики. В эпитаксиальных слоях методом просвечивающей электронной микроскопии поперечных сечений обнаружены дислокации несоответствия. Эти дефекты вызывают аномалии в электрических характеристиках. Показано, что, несмотря на эти аномалии, электрические измерения обеспечивают полезную и надежную информацию о структурах.Досліджєно дефекти у гетероструктурах Si/SiGe та їх єлєктричні характеристики. В епітаксиальних шарах методом просвічувальної електронної мікроскопії поперечних перерізів виявлено дислокації невідповідності. Ці дефекти спричиняють аномалії в електричних характеристиках. Показано, що, незважаючи на ці аномалії, електричні вимірювання забезпечують корисну та надійну інформацію про структури

Molecular phylogeny and biogeography of caecilians from Southeast Asia (Amphibia, Gymnophiona, Ichthyophiidae), with special reference to high cryptic species diversity in Sundaland

We investigated the phylogenetic relationships and estimated the history of species diversification and character evolution in two ichthyophiid genera: Caudacaecilia and Ichthyophis. We estimated the phylogenetic relationships of 67 samples from 33 localities in Southeast Asia from 3840-bp sequences of the mitochondrial 12S rRNA, 16S rRNA, and cyt b genes using Bayesian inference, maximum likelihood, and maximum parsimony methods. The Southeast Asian samples formed a well-supported clade differentiated from a South Asian sample. The Southeast Asian clade was divided into two subclades, one containing samples from South China, Indochina, Malay Peninsula, and Java. The other consisted of samples from Borneo and the Philippines. Neither Caudacaecilia nor Ichthyophis was monophyletic, nor did samples with or without light stripes lateral to the body form clades. We found several distinct sympatric lineages and undescribed species, especially from Sundaland

Multiplicação in vitro do porta-enxerto de Prunus spp. 'Carelli' In vitro multiplication of Prunus spp. rootstocks 'Carelli'

No Brasil, a falta de porta-enxertos para as Prunáceas, principalmente de origem clonal, tem incentivado a seleção de novas variedades e o uso de técnicas de cultura in vitro para a propagação. Neste sentido, o objetivo deste trabalho foi avaliar o potencial de multiplicação in vitro do porta-enxerto 'Carelli' sob efeito de diferentes concentrações da citocinina 6-benzilaminopurina (BAP). Segmentos nodais com 0,5 cm de comprimento foram inoculados em meio de cultura de Lepoivre, suplementado com 0,0; 0,5; 1,0; 2,0 e 4,0 mg.L-1 BAP. Estes segmentos nodais são oriundos de plântulas preestabelecidas in vitro, após duas subculturas em meio de cultura de Lepoivre, suplementado com 0,5 mg.L-1 de BAP. As avaliações para número de brotos por explante e altura média das brotações foram realizadas após 21 dias de cultura in vitro. Os resultados mostraram que os tratamentos com BAP não apresentaram diferenças significativas entre si. A taxa média de multiplicação foi de 3,3 a 3,4 brotos por explante. O tratamento sem adição de BAP não apresentou a formação de brotações axilares, mas resultou em brotos com maior altura média (16,2 mm). O uso de BAP afetou significativamente a altura das brotações, e o acréscimo nas suas concentrações reduziu o comprimento das mesmas. Concentrações de BAP superiores a 1,0 mg.L-1de BAP reduziram o comprimento das brotações e promoveram hiperidricidade. O uso de 0,5 mg.L-1 de BAP promoveu a formação de 3,3 brotos por explante com 11,0 mm de altura média, em condições adequadas para o enraizamento.<br>In Brazil the lack of well adapted rootstocks in the Peach industry, mainly of clonal origin, forces the selection of new varieties and the use of tissue culture techniques for the mass clonal propagation. In the present work it was evaluated the in vitro multiplication potential of "Carelli" rootstock in response to different levels of BA. Nodal segments (0.5 cm length) were inoculated in test tubes containing 20 ml of Lepoivre culture medium supplemented with 0.0; 0.5; 1.0; 2.0 and 4.0 mg.L-1 BA. This nodal segments were originated from in vitro pre-established plants after two subcultures in Lepoivre culture medium supplemented with 0.5 mg.L-1 BA. Evaluations done after 21 days in culture showed that the different levels of BA resulted in values statistically similar for the multiplication rate and length of regenerated shoots. The values for multiplication rate ranged from 3.3 to 3.4 shoots/explant. The treatment control did not result in multiple shoots but showed shoots with the highest lengh (16.2 mm). BA significativelly affected the length of shoots and the increase in its levels reduced the shoot lengh. BA levels higher than 1.0 mg.L-1 reduced the shoot length and promoted vitrification. BA in the level of 0.5 mg.L-1 resulted in the induction of 3.3 shoots/explant with means values of 11.0 mm in length in adequate conditions for rooting