A study of the ferromagnetic transition of SrRuO3SrRuO_3 in nanometer thick bilayers with YBa2Cu3OyYBa_2Cu_3O_y, La1.88Sr0.12CuO4−yLa_{1.88}Sr_{0.12}CuO_{4-y}, Au and Cr: Signature of injected carriers in the pseudogap regime

The hypothesis regarding the existence of uncorrelated pre-formed pairs in the pseudogap regime of superconducting $YBa_2Cu_3O_y$ is tested experimentally using bilayers of $YBa_2Cu_3O_y$ and the itinerant ferromagnet $SrRuO_3$. In our study, we monitor the influence of $YBa_2Cu_3O_y$ on $T_p$, the ferromagnetic ordering temperature of $SrRuO_3$. Here, $T_p$ is the temperature of maximum dM/dT or dR/dT where M and R are the magnetization and resistance of $SrRuO_3$, respectively. We compare the results with similar measurements carried out on bilayers of $La_{1.88}Sr_{0.12}CuO_{4-y}$, $Au$ and $Cr$ with $SrRuO_3$. We find that in bilayers made of underdoped 10 nm $YBa_2Cu_3O_y$/5 nm $SrRuO_3$, the $T_p$ values are shifted to lower temperatures by up to 6-8 K as compared to $T_p\approx 140$ K of the 5 nm thick reference $SrRuO_3$ film. In contrast, in the other type of bilayers, which are not in the pseudogap regime near $T_p$, only a smaller shift of up to $\pm$2 K is observed. These differences are discussed in terms of a proximity effect, where carriers from the $YBa_2Cu_3O_y$ layer are injected into the $SrRuO_3$ layer and vice versa. We suggest that correlated electrons in the pseudogap regime of $YBa_2Cu_3O_y$ are responsible for the observed large $T_p$ shifts.Comment: 9 figure

Support during birth interacts with prior trauma and birth intervention to predict postnatal post-traumatic stress symptoms

Background: Many women experience childbirth as traumatic and 2% develop post-traumatic stress disorder (PTSD). This study examined the role of health practitioner support and personal control during birth as predictors of PTS symptoms, adjusting for vulnerability factors of prior trauma, depression, control beliefs and birth intervention. It also investigated interactions between support, prior trauma and birth intervention and their association with PTS symptoms. Methods: A prospective longitudinal survey of 138 women recruited from UK NHS maternity clinics. Measures were taken in pregnancy, three-weeks and three-months after the birth. Results: Support and control during birth were not predictive of postnatal PTS symptoms. However, support was predictive of PTS symptoms in a subset of women with prior trauma (beta = -.41, R2 = 16%) at both three-weeks and three-months postpartum. The interaction of birth intervention and support was associated with PTS symptoms three-months after birth, the relationship between support and PTS symptoms was stronger in women experiencing more intervention. Conclusions: Low support from health practitioners is predictive of postnatal PTS symptoms in women who have a history of trauma. Longer-term effects of low support on postnatal PTS symptoms are also found in women who had more intervention during birth

Computer numerical control vertical machining centre feed drive modelling using the transmission line technique

This study presents a novel application of the Transmission Line Matrix Method (TLM) for the modelling of the dynamic behaviour of non-linear hybrid systems for CNC machine tool drives. The application of the TLM technique implies the dividing of the ball-screw shaft into a number of identical elements in order to achieve the synchronisation of events in the simulation, and to provide an acceptable resolution according to the maximum frequency of interest. This entails the use of a high performance computing system with due consideration to the small time steps being applied in the simulation. Generally, the analysis of torsion and axial dynamic effects on a shaft implies the development of independent simulated models. This study presents a new procedure for the modelling of a ball-screw shaft by the synchronisation of the axial and torsion dynamics into the same model. The model parameters were obtained with equipments such as laser interferometer, ball bar, electronic levels, signal acquisition systems etc. The MTLM models for single and two-axis configurations have been simulated and matches well with the measured responses of machines. The new modelling approach designated the Modified Transmission Line Method (MTLM) extends the TLM approach retaining all its inherent qualities but gives improved convergence and processing speeds. Further work since, not the subject of this paper, have identified its potential for real time application

On the link between Amazonian forest properties and shallow cumulus cloud fields

During the dry season the Amazon forest is frequently covered by shallow cumulus clouds fields, referred to here as forest cumulus (FCu). These clouds are shown to be sensitive to land cover and exhibit a high level of spatial organization. In this study we use satellite data to perform a morphological classification and examine the link between FCu cloud field occurrence and the enhanced vegetation index (EVI), which is commonly used as a measure for forest density and productivity. Although weaker than first-order effects of meteorology, a clear positive linear relation between EVI (i.e., surface properties) and FCu field occurrence is seen over forest land cover, implying a strong coupling between forest surface fluxes and the cloud organization above. Over non-forest land cover the relationship between EVI and FCu occurrence is nonlinear, showing a reduction of FCu for high EVI values. We find that forest to non-forest transition zones display a superposition of the two different land cover dependencies

The role of intermolecular coupling in the photophysics of disordered organic semiconductors: Aggregate emission in regioregular polythiophene

We address the role of excitonic coulping on the nature of photoexcitations in the conjugated polymer regioregular poly(3-hexylthiophene). By means of temperature-dependent absorption and photoluminescence spectroscopy, we show that optical emission is overwhelmingly dominated by weakly coupled H-aggregates. The relative absorbance of the 0-0 and 0-1 vibronic peaks provides a powerfully simple means to extract the magnitude of the intermolecular coupling energy, approximately 5 and 30 meV for films spun from isodurene and chloroform solutions respectively.Comment: 10 pages, 4 figures, published in Phys. Rev. Let