Search results for "Microscope"

Stain-free virtual histology of Bombus terrestris compound eyes by laboratory phase-contrast nano-CT

2021

The visual systems of pollinating insects are studied to understand the effects of a changing environment, and are to date imaged using microscopy or micro-CT. Microscopy only allows two-dimensional imaging and conventional micro-CT requires heavy-metal staining of the samples. Here we present virtual histology of compound eyes of bumblebee (Bombus terrestris) using a laboratory nano-CT system. Propagation-based phase-contrast CT allows three-dimensional imaging of samples without using any staining. Micrometre-resolution images of the microanatomy of the eyes were reconstructed, and the features identified in CT (cornea, crystalline cones, pigment, photoreceptor cells, basement membrane) w…

Flow Cytometry versus Fluorescence Microscopy

1996

Since the pioneer work of the botanist Matthias Jakob Schleiden and the zoologist Theodor Schwann in 1839, and of Rudolph Virchow in 1859, cell research progressed in two opposite directions. Cell biologists focused their increasingly more powerful microscopies into the cell structure to reveal the great morphological complexity of the cytoplasm. A growing number of subcellular organelles thus challenged the early biochemists to discover their specific molecular features and their coordination to maintain an ordered cell life. The biochemists’ answer to such a challenge consisted usually in tearing apart cells into their discrete components and obtaining information on molecules and pathway…

PLA graphene nanoplatelets nanocomposites: Physical properties and release kinetics of an antimicrobial agent

2017

Abstract Graphene nanoplatelets (GnP) as filler and ciprofloxacin (CFX) as biocide were incorporated via melt-compounding into poly(lactic acid) (PLA) to obtain biopolymer-based nanocomposites with antimicrobial properties. GnP were added with the aim of improving the mechanical properties of the antimicrobial system and tuning the drug release. The obtained systems were mechanically characterized in tensile mode by quasi-static and dynamic mechanical tests. Furthermore, rheological measurements were performed. The morphology of the samples was analyzed through scanning electron microscopy (SEM). Moreover, a mathematical model, i.e. power law model, was used to fit the release data in order…

Effect of Graphene Nanoplatelets on the Physical and Antimicrobial Properties of Biopolymer-Based Nanocomposites

2016

In this work, biopolymer-based nanocomposites with antimicrobial properties were prepared via melt-compounding. In particular, graphene nanoplatelets (GnPs) as fillers and an antibiotic, i.e., ciprofloxacin (CFX), as biocide were incorporated in a commercial biodegradable polymer blend of poly(lactic acid) (PLA) and a copolyester (BioFlex®). The prepared materials were characterized by scanning electron microscopy (SEM), and rheological and mechanical measurements. Moreover, the effect of GnPs on the antimicrobial properties and release kinetics of CFX was evaluated. The results indicated that the incorporation of GnPs increased the stiffness of the biopolymeric matrix and allowed for the t…

Imaging and Ion-Beam Milling of Biological Specimens with the Helium-Ion Microscope

2021

Genesis of amorphous calcium carbonate containing alveolar plates in the ciliate Coleps hirtus (Ciliophora, Prostomatea).

2013

7 pages; International audience; In the protist world, the ciliate Coleps hirtus (phylum Ciliophora, class Prostomatea) synthesizes a peculiar biomineralized test made of alveolar plates, structures located within alveolar vesicles at the cell cortex. Alveolar plates are arranged by overlapping like an armor and they are thought to protect and/or stiffen the cell. Although their morphology is species-specific and of complex architecture, so far almost nothing is known about their genesis, their structure and their elemental and mineral composition. We investigated the genesis of new alveolar plates after cell division and examined cells and isolated alveolar plates by electron microscopy, e…

Temperature-induced microstructural changes in shells of laboratory-grown Arctica islandica (Bivalvia).

2021

Bivalve shells are increasingly used as archives for high-resolution paleoclimate analyses. However, there is still an urgent need for quantitative temperature proxies that work without knowledge of the water chemistry–as is required for δ18O-based paleothermometry–and can better withstand diagenetic overprint. Recently, microstructural properties have been identified as a potential candidate fulfilling these requirements. So far, only few different microstructure categories (nacreous, prismatic and crossed-lamellar) of some short-lived species have been studied in detail, and in all such studies, the size and/or shape of individual biomineral units was found to increase with water temperat…

Casimir-Polder force density between an atom and a conducting wall

2007

In this paper we calculate the Casimir-Polder force density (force per unit area acting on the elements of the surface) on a metallic plate placed in front of a neutral atom. To obtain the force density we use the quantum operator associated to the electromagnetic stress tensor. We explicitly show that the integral of this force density over the plate reproduces the total force acting on the plate. This result shows that, although the force is obtained as a sum of surface element-atom contributions, the stress-tensor method includes also nonadditive components of Casimir-Polder forces in the evaluation of the force acting on a macroscopic object.

Crystalline microstructure of boehmites studied by multi-peak analysis of powder X-ray diffraction patterns

2017

Nanocrystalline boehmite (gamma-aluminium-oxyhydroxide) is a material of industrial importance, the functionality of which follows from its crystalline microstructure. A procedure for preparing boehmite nanoparticles, comprising the formation of a precipitate by the alkalization of an aqueous solution of aluminium nitrate and subsequent hydrothermal aging, was previously elaborated. The application of an additive (maltitol or tartaric acid) to control the sizes and shapes of crystallites in the produced polycrystalline powder of boehmite was developed. The aim of this work is a study of the effect of the hydrothermal treatment time on nanocrystalline characteristics of boehmite, both in abs…

Osseous response on linear and cyclic RGD-peptides immobilized on titanium surfaces in vitro and in vivo

2017

Biomimetic surface modifications of titanium implants using the Arg-Gly-Asp-sequence (RGD) are promising to accelerate bone healing in cases of medical implants. Therefore, we compared the impact of linear and cyclic RGD (l- and c-RGD) covalently coupled onto titanium surfaces on the osseous response in vitro and in vivo. In vitro, osteoblasts' behaviour on different surfaces (unmodified, amino-silanized (APTES), l- and c-RGD) was analysed regarding adhesion (fluorescence microscopy), proliferation (resazurin stain) and differentiation (RT-PCR on alkaline phosphatase (AP) & osteocalcin (OC)). In vivo, osteosynthesis screws (unmodified n=8, l-RGD n=8, c-RGD n=8) were inserted into the proxim…