Time Transmission Electron Microscopy Research Articles

Anatomy of the Tantulocarida: first results obtained using TEM and CLSM. Part I: tantulus larva

The morphology of Tantulocarida, a group of minutely sized ectoparasitic Crustacea, is described here using for the first time transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). This enabled a detailed analysis of their internal anatomy to a level of detail not possible with previous light microscopic investigations. We studied the infective stage, the tantulus larva, attached on the crustacean host in two species, Arcticotantulus pertzovi and Microdajus tchesunovi, and put special emphasis on cuticular structures, muscles, adhesive glands used in attachment, sensory and nervous systems, and on the organs used in obtaining nutrients from the host. This allowed description of structures that have remained enigmatic or unknown until now. A doubly folded cuticular attachment disc is located at the anterior-ventral part of the cephalon and used for gluing the larva to the host surface with a cement substance released under the disc. Four cuticular canals run from a cement gland, located ventrally in the cephalon, and enter an unpaired, cuticular proboscis. The proboscis can be protruded outside through a separate opening above the mouth and is used for releasing cement. An unpaired and anteriorly completely solid cuticular stylet is located centrally in the cephalon and is used only for making a 1-μm-diameter hole in the host cuticle, through which passes a rootlet system used for obtaining nutrients. The rootlet system is a direct extension of the anterior gut of the tantulus, but inside the host, it consists of cuticle only. Several muscular systems seem to degenerate very quickly after the tantulus has settled on the host. The central nervous system is reduced to an absolute minimum in terms of both cell size and number. We discuss the morphology of the tantulus in light of the Tantulocarida being a sister group to the Thecostraca or even nested within that taxon.

Real time nanoscale structural evaluation of gold structures on Si (100) surface using in-situ transmission electron microscopy

Transport behavior of gold nanostructures on Si(100) substrate during annealing under high vacuum has been investigated using in-situ real time transmission electron microscopy (TEM). A comparative study has been done on the morphological changes due to annealing under different vacuum environments. Au thin films of thickness ∼2.0 nm were deposited on native oxide covered silicon substrate by using thermal evaporation system. In-situ real time TEM measurements at 850 °C showed the isotropic growth of rectangular/square shaped gold-silicon alloy structures. During the growth, it is observed that the alloying occurs in liquid phase followed by transformation into the rectangular shapes. For similar system, ex-situ annealing in low vacuum (10−2 millibars) at 850 °C showed the spherical gold nanostructures with no Au-Si alloy formation. Under low vacuum annealing conditions, the rate of formation of the oxide layer dominates the oxide desorption rate, resulting in the creation of a barrier layer between Au and Si, which restricts the inter diffusion of Au in to Si. This work demonstrates the important role of interfacial oxide layer on the growth of nanoscale Au-Si alloy structures during the initial growth. The time dependent TEM images are presented to offer a direct insight into the fundamental dynamics of the sintering process at the nanoscale.

Abrikosov fluxoid pinning in Al-13.5 at % Ag alloy by magnetic and torque measurements

The pinning force in a supersaturated solid solution of Al-13.5 at % Ag with defect structures of various types (Guinier-Preston zones, γ′- and γ-phase lamellae) formed by isothermal aging treatment has been investigated. To determine the fluxoid pinning force, both mechanical and magnetic techniques were used. At the same time transmission electron microscopy and optical microscopy observations were carried out. An increase of the pinning force with the decay of the alloy was observed.