Going beyond histology. Synchrotron micro-computed tomography as a methodology for biological tissue characterization: from tissue morphology to individual cells

Current light microscopic methods such as serial sectioning, confocal microscopy or multiphoton microscopy are severely limited in their ability to analyse rather opaque biological structures in three dimensions, while electron optical methods offer either a good three-dimensional topographic visualization (scanning electron microscopy) or high-resolution imaging of very thin samples (transmission electron microscopy). However, sample preparation commonly results in a significant alteration and the destruction of the three-dimensional integrity of the specimen. Depending on the selected photon energy, the interaction between X-rays and biological matter provides semi-transparency of the specimen, allowing penetration of even large specimens. Based on the projection-slice theorem, angular projections can be used for tomographic imaging. This method is well developed in medical and materials science for structure sizes down to several micrometres and is considered as being non-destructive. Achieving a spatial and structural resolution that is sufficient for the imaging of cells inside biological tissues is difficult due to several experimental conditions. A major problem that cannot be resolved with conventional X-ray sources are the low differences in density and absorption contrast of cells and the surrounding tissue. Therefore, X-ray monochromatization coupled with a sufficiently high photon flux and coherent beam properties are key requirements and currently only possible with synchrotron-produced X-rays. In this study, we report on the three-dimensional morphological characterization of articular cartilage using synchrotron-generated X-rays demonstrating the spatial distribution of single cells inside the tissue and their quantification, while comparing our findings to conventional histological techniques

One-Dimensional Nanostructures and Devices of II–V Group Semiconductors

The II–V group semiconductors, with narrow band gaps, are important materials with many applications in infrared detectors, lasers, solar cells, ultrasonic multipliers, and Hall generators. Since the first report on trumpet-like Zn3P2nanowires, one-dimensional (1-D) nanostructures of II–V group semiconductors have attracted great research attention recently because these special 1-D nanostructures may find applications in fabricating new electronic and optoelectronic nanoscale devices. This article covers the 1-D II–V semiconducting nanostructures that have been synthesized till now, focusing on nanotubes, nanowires, nanobelts, and special nanostructures like heterostructured nanowires. Novel electronic and optoelectronic devices built on 1-D II–V semiconducting nanostructures will also be discussed, which include metal–insulator-semiconductor field-effect transistors, metal-semiconductor field-effect transistors, andp–nheterojunction photodiode. We intent to provide the readers a brief account of these exciting research activities

Unresponsive wakefulness syndrome: a new name for the vegetative state or apallic syndrome

BACKGROUND: Some patients awaken from coma (that is, open the eyes) but remain unresponsive (that is, only showing reflex movements without response to command). This syndrome has been coined vegetative state. We here present a new name for this challenging neurological condition: unresponsive wakefulness syndrome (abbreviated UWS). DISCUSSION: Many clinicians feel uncomfortable when referring to patients as vegetative. Indeed, to most of the lay public and media vegetative state has a pejorative connotation and seems inappropriately to refer to these patients as being vegetable-like. Some political and religious groups have hence felt the need to emphasize these vulnerable patients' rights as human beings. Moreover, since its first description over 35 years ago, an increasing number of functional neuroimaging and cognitive evoked potential studies have shown that physicians should be cautious to make strong claims about awareness in some patients without behavioral responses to command. Given these concerns regarding the negative associations intrinsic to the term vegetative state as well as the diagnostic errors and their potential effect on the treatment and care for these patients (who sometimes never recover behavioral signs of consciousness but often recover to what was recently coined a minimally conscious state) we here propose to replace the name. CONCLUSION: Since after 35 years the medical community has been unsuccessful in changing the pejorative image associated with the words vegetative state, we think it would be better to change the term itself. We here offer physicians the possibility to refer to this condition as unresponsive wakefulness syndrome or UWS. As this neutral descriptive term indicates, it refers to patients showing a number of clinical signs (hence syndrome) of unresponsiveness (that is, without response to commands) in the presence of wakefulness (that is, eye opening)

Direct correlation between the 31P MAS NMR response and the electronic structure of some Transition-Metal Phosphides

A series of binary transition metal phosphides (Ni3P, Ni12P5, Ni2P, Ni5P4, NiP, NiP2, FeP, FeP2, FeP4, VP2, CoP) were investigated by solid state 31P MAS NMR, leading to rather different lineshapes, shifts, relaxation times, and temperature-dependences. The electronic structures of these compounds were computed using various DFT codes, based either on plane waves PAW potentials (VASP), or on all-electron basis sets in the FPLAPW formalism (Wien2K). Depending on the electronic features of the phosphide, self-interaction corrected formalisms (DFT+U or PBE0 hybrid functional) were also used to reach a better description of the electronic ground state and to establish a correlation with the shape and the nature of the NMR signals. As a result of the analysis, the main categories are diamagnetic compounds (FeP4, NiP2) and metallic ones, either real (VP2) or with some electronic localisation in band tails (Ni12P5, Ni2P, Ni5P4, NiP), or with spin-polarized conduction bands (CoP, FeP). FeP2 appears somewhat ambiguous, both based on the various computational results and on the NMR characteristics. Besides, FeP4 is the only compound for which very clear J couplings resulting from P-P bonds were observed