Charge density waves tuned by biaxial tensile stress.

The precise arrangement and nature of atoms drive electronic phase transitions in condensed matter. To explore this tenuous link, we developed a true biaxial mechanical deformation device working at cryogenic temperatures, compatible with x-ray diffraction and transport measurements, well adapted to layered samples. Here we show that a slight deformation of TbTe3 can have a dramatic influence on its Charge Density Wave (CDW), with an orientational transition from c to a driven by the a/c parameter, a tiny coexistence region near a = c, and without space group change. The CDW transition temperature Tc displays a linear dependence with a / c - 1 while the gap saturates out of the coexistence region. This behaviour is well accounted for within a tight-binding model. Our results question the relationship between gap and Tc in RTe3 systems. This method opens a new route towards the study of coexisting or competing electronic orders in condensed matter.

Texture analysis of periventricular echogenicity on neonatal cranial ultrasound predicts periventricular leukomalacia.

BACKGROUND: White matter periventricular echogenicity detected in neonatal cranial ultrasound (US) scans may be followed by cystic periventricular leukomalacia (PVL) or might resolve. Serial US are therefore needed to clarify the outcome. Texture analysis is a computerized method to analyze images and distinguish findings that are undetectable by the human eye. OBJECTIVE: To test whether texture analysis can differentiate echogenicities that resolve from those that develop cystic PVL. MATERIAL AND METHODS: Neonates with echogenicities on their initial US scan were studied; texture analysis was performed on the coronal and sagittal sections. Texture parameters were entered into a linear discriminant analysis (LDA) to classify the scans along two axes called most discriminant features (MDF) 1 and 2. RESULTS: We studied twenty infants with periventricular echogenicities on initial scans; ten of them later resolved (group A), while the other ten infants developed cystic PVL (group B). The classification accuracy was 66% and 82% for group A and B on sagittal sections, and 75%, and 80% on coronal. In the coronal and sagittal plane respectively, a MDF1 value of 0.98 and 0.24 and an MDF2 value of 0.86 and 0.001 provided the best sensitivity, specificity, positive and negative likelihood ratio. CONCLUSION: Texture analysis is a promising objective tool to early identify which cranial echogenicity that will develop into cystic PVL.