Cerebral autoregulation, brain injury, and the transitioning premature infant

Improvements in clinical management of the preterm infant have reduced the rates of the two most common forms of brain injury, such as severe intraventricular hemorrhage and white matter injury, both of which are contributory factors in the development of cerebral palsy. Nonetheless, they remain a persistent challenge and are associated with a significant increase in the risk of adverse neurodevelopment outcomes. Repeated episodes of ischemia–reperfusion represent a common pathway for both forms of injury, arising from discordance between systemic blood flow and the innate regulation of cerebral blood flow in the germinal matrix and periventricular white matter. Nevertheless, establishing firm hemodynamic boundaries, as a part of neuroprotective strategy, has challenged researchers. Existing measures either demonstrate inconsistent relationships with injury, as in the case of mean arterial blood pressure, or are not feasible for long-term monitoring, such as cardiac output estimated by echocardiography. These challenges have led some researchers to focus on the mechanisms that control blood flow to the brain, known as cerebrovascular autoregulation. Historically, the function of the cerebrovascular autoregulatory system has been difficult to quantify; however, the evolution of bedside monitoring devices, particularly near-infrared spectroscopy, has enabled new insights into these mechanisms and how impairment of blood flow regulation may contribute to catastrophic injury. In this review, we first seek to examine how technological advancement has changed the assessment of cerebrovascular autoregulation in premature infants. Next, we explore how clinical factors, including hypotension, vasoactive medications, acute and chronic hypoxia, and ventilation, alter the hemodynamic state of the preterm infant. Additionally, we examine how developmentally linked or acquired dysfunction in cerebral autoregulation contributes to preterm brain injury. In conclusion, we address exciting new approaches to the measurement of autoregulation and discuss the feasibility of translation to the bedside

Belgian corporate finance in a European perspective

When analysing corporate finance, it is necessary to take account of various factors which may cause significant disparities between firms, such as their size and their sector of activity. Taking account of the size aspect, by neutralising sectoral disparities, there are few differences between the debt levels of small, medium-sized and large firms. Conversely, the debt structure appears to depend on the firm’s size : small firms are more dependent on bank loans. That is confirmed by the high degree to which they make use of credit facilities. Nonetheless, surveys indicate that access to finance is not a major constraint for SMEs, be they Belgian or European : they perceive access to finance, and more specifically access to bank finance, as relatively easy. In contrast, the financial structure of firms differs widely between sectors, and depends to a great extent on the associated intrinsic activity and the scale of the investments. Sectors with high investment ratios, such as the transport and communication sector or the energy sector, mainly use long-term finance. Ample equity capital enables them to maintain a balanced financial situation. Conversely, highly labour-intensive sectors, such as construction or trade, display much higher debt-to-equity ratios ; their debts are mainly short term and they make extensive use of trade credit. A more detailed analysis of the manufacturing sector also reveals differences of financial structure between firms which are classed as innovative and those which are not. In particular, if the chemical industry is excluded, the firms in the innovative sectors make less use of bank loans and record more short-term debt than firms in non-innovative sectors. That may reflect the lenders’ desire to limit the risk incurred, particularly by using the threat of non-renewal of the loan to encourage the manager to behave efficiently. The qualitative surveys appear to indicate that the financial constraint is felt more by innovative firms than by SMEs in general. That expresses a financing need specific to innovative SMEs. At the early stages in their development, they depend almost exclusively on the entrepreneur’s personal resources and those of his friends and family, and venture capital only takes over in the later stages. Finally, as regards the financing structure, a comparison between Belgian firms and their European counterparts, after neutralising the specific effects of size and sector, indicates that the former issue larger amounts of capital. Abundant intra-group financial flows and a favourable institutional context are conducive to that situation.bank lending, venture capital, corporate finance.

The financial situation of non-financial corporations

As entities where the production process takes place, non financial corporations deserve full attention in the analysis of the real and financial accounts. However, the examination of the financial behaviour of non financial corporations is traditionally confined to their financing : thus, the Bank’s annual report generally only considers their liabilities. Yet the formation of financial assets by non financial corporations is a significant item of information, in both statistical and economic terms. The total financial assets held by non financial corporations in Belgium are considerable, as they far exceed the total financial assets of households. A study recently revealed the historically high level of financial asset formation by non financial corporations in the main industrialised countries, a factor which could help to explain the relatively low level of long-term interest rates. In recent years, Belgian non financial corporations have formed substantially more financial assets than their counterparts in the euro area. In 2005, the financial assets held by Belgian companies were – partly for that reason – almost double the financial assets, expressed in percentages of GDP, of non financial corporations in the euro area. However, this situation certainly does not indicate any risk aversion on the part of Belgian non financial corporations. In fact the liabilities side of their balance sheets also records growth of new financial liabilities in excess of the figure for non financial corporations in the euro area, so that – in terms of liabilities, too – the outstanding total in Belgium is comparatively much higher than the outstanding total in the euro area. This paradoxical situation of Belgian non financial corporations – the fact that they hold much more substantial assets while at the same time contracting significantly greater liabilities – is due to the fact that the Belgian non financial corporations sector includes coordination centres and non financial holding companies, i.e. undertakings acting, as it were, as financial intermediaries. If the coordination centres and non financial holding companies are excluded, the overall outstanding total gross assets and liabilities of Belgian non financial corporations reverts to a level very close to the figure for the euro area. Finally, in 2005 Belgian non financial institutions recorded an outstanding total of net liabilities amounting to around 100 p.c. of GDP, i.e. slightly more than the outstanding total for non financial corporations in the euro area. It is also apparent that the exclusion of the coordination centres and non financial holding companies has hardly any effect on Belgium’s net debtor position, confirming that these two types of institutions perform an intermediary function. Although it is not possible to isolate the coordination centres and non financial holding companies in the case of new transactions (flows), there is no reason to think that the effect would be any different : there would be a significant decline in the gross flows of new assets and liabilities, but that would have a negligible influence on the financial balance. That balance is very similar to the one for the euro area.flow of funds, corporate finance

Performance of polar codes for quantum and private classical communication

We analyze the practical performance of quantum polar codes, by computing rigorous bounds on block error probability and by numerically simulating them. We evaluate our bounds for quantum erasure channels with coding block lengths between 2^10 and 2^20, and we report the results of simulations for quantum erasure channels, quantum depolarizing channels, and "BB84" channels with coding block lengths up to N = 1024. For quantum erasure channels, we observe that high quantum data rates can be achieved for block error rates less than 10^(-4) and that somewhat lower quantum data rates can be achieved for quantum depolarizing and BB84 channels. Our results here also serve as bounds for and simulations of private classical data transmission over these channels, essentially due to Renes' duality bounds for privacy amplification and classical data transmission of complementary observables. Future work might be able to improve upon our numerical results for quantum depolarizing and BB84 channels by employing a polar coding rule other than the heuristic used here.Comment: 8 pages, 6 figures, submission to the 50th Annual Allerton Conference on Communication, Control, and Computing 201

Improving visuo-motor coordination in non-dominant hands through tracing tasks

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaf 21).Visuo-motor skills are essential in the performance of various everyday tasks. These skills can be impaired in several neurological conditions. Effective rehabilitation schemes are needed in order to improve visuo-motor coordination in such subjects. This study will propose and test a training regimen as a potential approach for improving fine eye-hand coordination. It will also seek to understand the significance of feedback in visuo-motor improvement. We tested three groups of subjects: those who received training with feedback, those who received training without feedback, and a control group that received no training. The results indicate the effectiveness of our training routine and also highlight the importance of feedback in improving eye-hand coordination.by Zachary M. Eisenstat.S.B