Understanding Musical Sound with Forward Models and Physical Models

This research report describes an approach to parameter estimation for physical models of sound-generating systems using distal teachers and forward models (Jordan & Rumelhart, 1992; Jordan, 1990). The general problem is to find an inverse model of a sound-generating system that transforms sounds to action parameters; these parameters constitute a model-based description of the sound. We first show that a two-layer feedforward model is capable of performing inverse mappings for a simple physical model of a violin string. We refer to this learning strategy as direct inverse modeling; it requires an explicit teacher and it is only suitable for convex regions of the parameter space. A model of two strings was implemented that had non-convex regions in its parameter space. We show how the direct modeling strategy failed at the task of learning the inverse model in this case and that forward models can be used, in conjunction with distal teachers, to bias the learning of an inverse model so that non-convex regions are mapped to single-point solutions in the parameter space. Our results show that forward models are appropriate for learning to map sounds to parametric representations

Up-regulation interleukin-6 and interleukin-8 by activated protein C in lipopolysaccharide-treated human umbilical vein endothelial cells

Objective: To investigate the effect of activated protein C (APC) on inflammatory responses in human umbilical vein endothelial cells (HUVEC) stimulated with lipopolysaccharide (LPS). Methods: The second passage of collagenase digested HUVEC was divided into the following groups: serum free medium control group (SFM control), phosphate buffer solution control group (PBS control), LPS group with final concentration of 1 μg/ml (LPS group), APC group with final concentration of 7 μg/ml, Pre-APC group (APC pretreatment for 30 min prior to LPS challenge), and Post-APC group (APC administration 30 min after LPS challenge). Supernatant was harvested at 0, 4, 8, 12 and 24 h after LPS challenge. Interleukin-6 (IL-6) and Interleukin-8 (IL-8) levels were analyzed with ELISA. Cells were harvested at 24 h after LPS challenge, and total RNA was extracted. Messenger RNA levels for IL-6 and IL-8 were semi-quantitatively determined by RT-PCR. Results: Compared with control group, IL-6 and IL-8 levels steadily increased 4 to 24 h after LPS stimulation. APC treatment could increase LPS-induced IL-6 and IL-8 production. The mRNA levels of IL-6 and IL-8 exhibited a similar change. Conclusion: APC can further increase the level of IL-6 and IL-8 induced by LPS. The effect of these elevated cytokines is still under investigation

The prevalence of anaemia, hypochromia and microcytosis in preoperative cardiac surgical patients

This retrospective study aimed to determine the prevalence of preoperative anaemia, hypochromia and microcytosis in cardiac surgery patients. Data was analysed for 943 patients (over a two-year period) undergoing coronary artery bypass graft, valve or combined coronary artery bypass graft and valve surgery at a tertiary hospital in South Australia. Overall prevalence of preoperative anaemia was 25.2%, greater in males than females (27.6 vs 19.9%, P 65 years of age (P=0.003). Anaemic patients with low red cell indices had lower preoperative haemoglobin than anaemic patients without low red cell indices (median haemoglobin 112 vs 120 g/l, P=0.008). Compared to non-anaemic patients, anaemic patients had higher transfusion rates (79.8 vs 46.4%, P <0.0001), which were greater in those with reduced red cell indices compared to those with normal red cell indices (93.5 vs 76.6%, P=0.01). This study demonstrated a high prevalence of preoperative anaemia, microcytosis and hypochromia in cardiac surgical patients.O David, R Sinha, K Robinson, D Cardon