1,721,216 research outputs found
The influence of mannitol on the volume of fluid given to adult patients during cardiopulmonary bypass
No full textDuring cardiopulmonary bypass, non-blood fluids are
added to the circulation via the priming of the circuit.
There is no standardisation of priming fluids between different cardiac centres, but most use a mixture of crystalloid and colloid. Mannitol, an osmotic diuretic, is often used in the prime with the aim of minimising renal damage. Although mannitol has no effect on renal function we have noticed that it reduces the amount of additional fluid given to maintain reservoir volume. This study aims at examining the effects of mannitol on fluid balance during cardiopulmonary bypass
Auditory evoked potentials for monitoring during anaesthesia: a study of data quality
No full textThe auditory evoked potential termed the middle latency response (MLR) has been suggested as an indicator of adequacy of anaesthesia during surgery. However, the response is small and must be extracted from high levels of background noise. A key consideration in using the MLR for clinical monitoring is whether data quality is sufficient to detect small changes. The aim of this study was to investigate the quality of the MLR recorded during anaesthesia, as a rigorous analysis of data quality is lacking in many studies. MLR recordings from patients sedated in intensive care after cardiac surgery were compared to recordings from a reference group of young volunteers with normal hearing. Data quality was measured with the Fsp parameter. A bootstrap analysis was used to measure statistical response presence and to detect within-subject changes during clinical anaesthesia. Noise levels were high in the normative group probably due to myogenic and EEG activity. With 5 Hz click stimulation, MLR presence in the normative group was below 30%. Response presence improved using stimulation paradigms with chirps or maximum length sequences and reached 100% with a combination of maximum length sequences and chirps. Fsp values generally improved during anaesthesia as noise levels reduced and MLR presence was 100% for MLS click stimulation. Changes in the MLR amplitude with propofol infusion rate were small. Some within-subject changes in MLR amplitude were detected using the bootstrap analysis, but 100% detection was not possible. Conclusion: Obtaining good quality MLR data in awake subjects is challenging. Data quality improves during clinical anaesthesia and with advanced stimulation methods, but reliable detection of changes in the MLR for clinical monitoring remains a challenge
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The effect of mannitol on renal function after cardiopulmonary bypass in patients with established renal dysfunction
No full textThe usefulness of mannitol in the priming fluid for cardiopulmonary bypass is uncertain in patients with normal renal function, and has not been studied in patients with established renal dysfunction. We studied 50 patients with serum creatinine between 130 and 250 mu mol.l(-1) having cardiac surgery. Patients were randomised to receive mannitol 0.5 g.kg(-1), or an equivalent volume of Hartmann's solution, in the bypass prime. There were no differences between the groups in plasma creatinine or change in creatinine from baseline, urine output, or fluid balance over the first three postoperative days. We conclude that mannitol has no effect on routine measures of renal function during cardiac surgery in patients with established renal dysfunctio
A comparison of sequential total and activated white cell count in patients undergoing coronary artery bypass grafting, using cardiopulmonary bypass, with and without a white cell filter
No full textIntroduction
Cardiopulmonary bypass (CPB) has been shown to induce a systemic inflammatory response similar to the local reaction seen after tissue damage [1]. This leads to the release of toxic substances, such as elastase, which cause endothelial damage and may adversely affect outcome [2]. Use of a leucocyte depleting arterial line filter is one of many anti-inflammatory strategies that are undergoing evaluation. Leucocyte depleting filters may be capable of selectively removing activated white cells [3], but this has not been proved in vivo. The aim of the present study was to compare sequential total and activated white cells during CPB, using either a leucocyte depleting or standard arterial line filter.
Materials and methods
After local ethical committee approval, 20 patients undergoing coronary artery bypass grafting using CPB were prospectively randomly allocated to have either a Leukogard LG–6 (Pall Biomedical, Portsmouth, UK) or a nonleucocyte depleting filter inserted into the arterial line of the CPB circuit. Arterial limb blood samples were taken immediately after institution of CPB (0min) and at 10–min intervals throughout the bypass period. Activated white cells were identified using nitroblue tetrazolium, then both total and activated white cell numbers counted after staining with Leucoplate.Results
Table 1 shows the number of white cells counted/1.25 ? l (volume of a single channel of Nageotte counting chamber) using light microscopy (× 25).Conclusion
The LG6 leucocyte filter reduces the total white cell count and is capable of selectively removing activated white cells during CPB. The exact relationship between leucocyte depletion and improved patient outcome still remains unclear
Development of a nanowire-based test bed device for molecular electronics applications
No full textIn this paper, we present a novel test bed system which we believe addresses several key challenges in molecular electronics, i.e., the need to fabricate metal-molecule-metal junctions that have the potential to facilitate single-molecule measurements, are easily characterized, and are reproducible. The system is based upon template-electrodeposited metal nanowires incorporating a self-assembled monolayer spacer that are fabricated into electrical devices using direct-write photolithography. Removal of the spacer leaves a nanometer-sized, characterizable gap to which nanoparticles or a test molecule of interest can be attached postfabrication. Here we report the fabrication procedure together with results showing the application of these devices to the study of the i/V characteristics of Au nanoparticles at cryogenic temperatures. These data demonstrate that the performance of these easily produced, inexpensive, novel devices compares favorably to that of devices made using preexisting methods
Letter to Nature. Growth of nanowire superlattice structures for nanoscale photonics and electronics
No full textThe assembly of semiconductor nanowires and carbon nanotubes into nanoscale devices and circuits could enable diverse applications in nanoelectronics and photonics1. Individual semiconducting nanowires have already been configured as field-effect transistors2, photodetectors3 and bio/chemical sensors4. More sophisticated light-emitting diodes5 (LEDs) and complementary and diode logic6-8 devices have been realized using both n- and p-type semiconducting nanowires or nanotubes. The n- and p-type materials have been incorporated in these latter devices either by crossing p- and n-type nanowires2, 5, 6, 9 or by lithographically defining distinct p- and n-type regions in nanotubes8, 10, although both strategies limit device complexity. In the planar semiconductor industry, intricate n- and p-type and more generally compositionally modulated (that is, superlattice) structures are used to enable versatile electronic and photonic functions. Here we demonstrate the synthesis of semiconductor nanowire superlattices from group III–V and group IV materials. (The superlattices are created within the nanowires by repeated modulation of the vapour-phase semiconductor reactants during growth of the wires.) Compositionally modulated superlattices consisting of 2 to 21 layers of GaAs and GaP have been prepared. Furthermore, n-Si/p-Si and n-InP/p-InP modulation doped nanowires have been synthesized. Single-nanowire photoluminescence, electrical transport and electroluminescence measurements show the unique photonic and electronic properties of these nanowire superlattices, and suggest potential applications ranging from nano-barcodes to polarized nanoscale LEDs
Optimization of plasmon–plasmon coupling in photorefractive layered media
Full text linkIn this paper we study grating-induced plasmon–plasmon coupling in photorefractive layered media using a weakcoupling approximation. The method used is applicable to general layered structures that support both plasmonic and optical modes, such as photorefractive liquid crystal cells. The approximate equations are accurate when compared to S matrix approaches and capture the plasmon propagation at the surface of the device along with the optical modes guided by the layered geometry underneath. Analysis of the resulting model provides insight into the effect of the control parameters in this device and the means to optimize the diffraction efficiency. For example, by considering the case in which the plasmon is spectrally separated from the guided modes it is possible to determine the optimum gold thickness and grating strength required to obtain the strongest possible diffraction
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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