Ultrasound-guided Placement of Permanent Hemodialysis Catheters Compared to the Traditional Blind Method

Background: Central venous hemodialysis catheters are one of the most common vascular accesses for patients suffering from end-stage kidney disease. The application of ultrasound-guided placement of permanent hemodialysis catheters is highly recommended by the new guidelines because of its advantages over the traditional blind methods.Methods: In this prospective study, the samples comprised patients (N=80) referred to a vascular surgery clinic by their nephrologist or elective vascular surgery consultations and asking for the placement of permanent hemodialysis catheters in Imam Hossain Hospital (A referral hospital complex center in, Tehran, Iran) during 2014 to 2015. The patients were randomly divided into two groups (n=40); one of the groups underwent the placement of catheters with the guidance of Doppler ultrasound and the other with the traditional blind method. Then, the data were analyzed by SPSS V. 21 software.Results: There was statistically significant fewer attempts for successful placement (Z= -2.725, P=0.006), less insertion failure (Chi-Square=9.600, P=0.002), fewer failures with the first attempt (Chi-square=9.600, P=0.002), and less total placement time (t=1.379, df=69.549, P=0.172) in the sonography-guided group compared to the blind method. Furthermore, there was no significant difference in venous cannulation time and complications such as pneumothorax, neck hematoma, and carotid puncture between the two groups. Moreover, the patients had significantly greater satisfaction with the sonography-guided method (Z=-4.306, P=0.0001).Conclusion: According to this study, it might be beneficial to use ultrasound as the first method of permanent hemodialysis catheters insertion and patients would be more satisfied with this approach as well. In addition, learning the blind method is recommended to the practitioners because of the possibility of lacking ultrasound in an emergency.

Traces of old and new center-periphery dynamics in language-in-education policy and practice

This article reveals how center-periphery relations have unfolded, over time, in language policy processes in one nation – Timor-Leste – on the global periphery. We take a longue durée perspective on the language policy processes at work in this historical context, showing how different regimes of language were imposed, in the past, by colonisers from distant centers – in Portugal and then in Java, Indonesia. Then, turning to the post-independence period, we show how a new order of indexicality, forged within the Resistance to the Indonesian occupation, formed the basis for current language policy in Timor-Leste, with Portuguese and Tetum as co-official languages. We also demonstrate that this agentive policy move, from the global periphery, oriented Timor-Leste to new and more complex center-periphery relations, to a ‘lusophone’ world, with Portugal and Brazil as key players. Our account of contemporary policy discourses in Timor-Leste, and of the consequences for language policy implementation, on different scales (national and local), draws on recent research of an ethnographic and multi-scalar nature conducted in Timor-Leste (Da Costa Cabral, 2015).

Structure and Phase Changes in Natural and Synthetic Magnesium Aluminum Spinel

Natural spinel crystals from Ural and Pamir deposits and synthetic magnesium aluminium spinel single crystals with different stoichiometry (MgO.nAl2O3 ) grown by Verneuil method were used. The photoluminescence (PL), its excitation (PLE) and optical absorption of stoichiometric and nonstoichiometric magnesium aluminium spinel crystals containing the chromium and manganese ions and defects produced by fast neutron irradiation( fluence up to 1020cm-2, E>0.1 MeV) are investigated. The broadening of R- and N-lines takes place in synthetic stoichiometric spinel. Structure of synthetic nonstoichiometric spinels (n>1) has to be more disordered, since in addition to the site exchange the so called stoichiometric vacancies are present in the structure. The R- and N-lines broadening takes place after spinel crystals irradiation by fast neutron too. The neutron irradiation causes increasing of the spinel inversion. Furthermore the great deviation from stoichiometry leads to the local structure of α-Al2O3 formation around Cr3+ ions. The orange emission band at 570 nm is belonging to complex center “Mn2+-F+ (or F centre)”.

Contrast sensitivity of MT receptive field centers and surrounds

Neurons throughout the visual system have receptive fields with both excitatory and suppressive components. The latter are responsible for a phenomenon known as surround suppression, in which responses decrease as a stimulus is extended beyond a certain size. Previous work has shown that surround suppression in the primary visual cortex depends strongly on stimulus contrast. Such complex center-surround interactions are thought to relate to a variety of functions, although little is known about how they affect responses in the extrastriate visual cortex. We have therefore examined the interaction of center and surround in the middle temporal (MT) area of the macaque ( Macaca mulatta) extrastriate cortex by recording neuronal responses to stimuli of different sizes and contrasts. Our findings indicate that surround suppression in MT is highly contrast dependent, with the strongest suppression emerging unexpectedly at intermediate stimulus contrasts. These results can be explained by a simple model that takes into account the nonlinear contrast sensitivity of the neurons that provide input to MT. The model also provides a qualitative link to previous reports of a topographic organization of area MT based on clusters of neurons with differing surround suppression strength. We show that this organization can be detected in the gamma-band local field potentials (LFPs) and that the model parameters can predict the contrast sensitivity of these LFP responses. Overall our results show that surround suppression in area MT is far more common than previously suspected, highlighting the potential functional importance of the accumulation of nonlinearities along the dorsal visual pathway.