Limited integration has stifled the Middle East and North Africa (MENA) region's ability to tap into its significant potential for economic growth and job creation. The MENA region is among the least ...integrated in the world economy. Although home to 5.5 percent of the world's population (on average for 2008-10) and 3.9 percent of the world's gross domestic product (GDP), the region's share of nonoil world trade is only 1.8 percent. By contrast, countries that have opted for a liberal trade and investment regime most notably in East Asia have experienced a significant increase in trade, employment, and per capita income. If petroleum and gas are taken into consideration, the MENA region is far more integrated in the world economy, with total exports accounting for 6.2 percent of total world trade. Exports of oil and gas represent about three-quarters of MENA's total exports. This study shows that, in spite of commendable reform efforts in recent years, the MENA region continues to face constraints to economic competitiveness in general, and trade barriers in particular. Of critical importance is the need to improve trade-related infrastructure and strengthen trade facilitation activities. Moreover, this study demonstrates that preferential trade agreements (PTAs), though helpful in many respects, do not significantly expand exports. Instead, the focus in must be on opening up to the rest of the world, which may require that individual countries aggressively pursue unilateral liberalization policies. While regional cooperation and integration can bring benefits, these efforts can also pose significant costs if not carried out in a manner that is compatible with broader global integration trends. Finally, while there is reasonable potential to enhance trade in goods, trade in services is a major untapped source of trade growth within the region and between the region and the rest of the world. The main objective of this report is to assess the achievements in, opportunities for, and challenges of deeper regional economic cooperation and integration within the MENA region and between the region and the rest of the world.
To measure cerebral blood flow in women with eclampsia and severe preeclampsia using phase-contrast magnetic resonance imaging (MRI).
Women with eclampsia and severe preeclampsia were studied and ...compared with normotensive cohorts. Magnetic resonance imaging studies were performed initially in hypertensive women after seizure treatment or prophylaxis was given. Magnetic resonance imaging flow measurements were made using a phase contrast velocity imaging technique in each middle and posterior cerebral artery. Conventional brain MRI and magnetic resonance angiography of the circle of Willis were performed at the time of flow measurement. Women with preeclampsia and eclampsia served as their own controls and were matched with normotensive cohorts. All of the hypertensive women were studied again 4-5 weeks postpartum. Paired t test analysis and an analysis of variance were performed. Considering a 20% minimum detectable difference in flow, the power was 0.80, 0.92, 0.86, and 0.96 for the left and right middle cerebral arteries and the left and right posterior cerebral arteries, respectively.
All 28 women enrolled were studied initially within 24 hours of delivery or of their most recent seizure. There were no significant differences in blood flow in either the posterior or middle cerebral arteries in women with eclampsia or severe preeclampsia between the initial studies and those 4-5 weeks postpartum, or compared with their normal counterparts. No findings of vasospasm were seen. T2-weighted brain images were markedly abnormal in all eight women with eclampsia, mildly abnormal in two of ten with severe preeclampsia, and normal in all ten controls.
No flow changes were seen in the posterior or middle cerebral arteries of women with eclampsia and severe preeclampsia despite the presence of remarkable brain lesions in all women with eclampsia. These findings question the role of vasospasm and cerebral hypoperfusion, although a vasodilatory effect of magnesium could not be excluded.
An important limitation of transcranial Doppler (TCD) ultrasonography is its inability to directly measure blood flow or vessel diameter. To extend the ability of TCD ultrasonography, indices were ...derived from an intensity-weighted mean of the entire Doppler spectrum. The objective of this article is to test the behavior of these indices under conditions of diameter constancy (hyper- and hypoventilation) and when vessel diameter decreases (vasospasm).
A flow index (FI) was calculated by averaging several heartbeats of spectral data and calculating the first spectral moment. An area index (AI) was defined as the FI divided by the mean velocity, motivated by the knowledge that vessel flow is the product of vessel diameter and mean velocity. To test the FI and the AI under conditions of diameter constancy, middle cerebral artery Doppler signals were obtained from 20 patients during conditions of hypercarbia, hypocarbia, and normocarbia. To test the ability of these indices to evaluate a decrease in vessel diameter, signals from 41 sites on 23 arteries were obtained from patients who underwent both TCD and angiographic studies on two separate occasions after the occurrence of subarachnoid hemorrhage. The changes in the AI were compared with the arterial diameters measured from angiograms.
The FI was proportional to the mean velocity in the cohort of healthy patients (r=0.97). The AI changed by less than 3% in the same cohort. The AI predicted the direction of the diameter change in all vessels showing angiographic changes in area. Changes in the AI and the measured angiographic changes in cross-sectional areas were correlated (overall, r=0.90; with two outlines removed, r=0.86).
This variant of the intensity-weighted mean predicts changes in vessel cross-sectional area under conditions of changes in CO2 and cerebral vasospasm. This preliminary study suggests that careful use of this tool may provide accurate evaluation of cerebral blood flow through the large vessels and quantitative changes in diameter, which occur frequently after subarachnoid hemorrhage.
Concern about the environment in colonial northern Nigeria developed out of a series of controversies and practices, particularly those relating to agriculture. Increasingly, local practices that ...have sustained the population and the environment for centuries are subjected to "scientific" scrutiny. Though many of these practices were either misunderstood or not understood at all, this did not stop the subjugation of local practices to "science". However, this "scientific" enterprise was often conflict-ridden, with important questions being resolved only after the intervention of political authorities. The resulting colonial practices in the fields of irrigation, forest management and the application of chemical fertilizer continue to dominate the thinking of state officials in post-colonial Nigeria, leading to unsustainable policies. An earlier colonial tradition of investigating the practices of local farmers and the constraints therein would have been a more appropriate basis for post-colonial policy.
Although transcranial Doppler ultrasound (TCD) has been used to detect oscillations in CBF, interpretation is severely limited, since only blood velocity and not flow is measured. Oscillations in ...vessel diameter could, therefore, mask or alter the detection of those in flow by TCD velocities. In this report, the authors use a TCD-derived index of flow to detect and quantify oscillations of CBF in humans at rest. A flow index (FI) was calculated from TCD spectra by averaging the intensity weighted mean in a beat-by-beat manner over 10 seconds. Both FI and TCD velocity were measured in 16 studies of eight normal subjects at rest every 10 seconds for 20 minutes. End tidal CO2 and blood pressure were obtained simultaneously in six of these studies. The TCD probe position was meticulously held constant. An index of vessel area was calculated by dividing FI by velocity. Spectral estimations were obtained using the Welch method. Spectral peaks were defined as peaks greater than 2 dB above background. The frequencies and magnitudes of spectral peaks of FI, velocity, blood pressure, and CO2 were compared with t tests. The Kolmogorov-Smirnov test was used to further confirm that the data were not white noise. In most cases, three spectral peaks (a, b, c) could be identified, corresponding to periods of 208 ± 93, 59 ± 31, and 28 ± 4 (SD) seconds for FI, and 196 ± 83, 57 ± 20, and 28 ± 6, (SD) seconds for velocity. The magnitudes of the spectral peaks for FI were significantly greater (P < 0.02) than those for velocity. These magnitudes corresponded to variations of at least 15.6%, 9.8%, and 6.8% for FI, and 4.8%, 4.2%, and 2.8% for velocity. The frequencies of the spectral peaks of CO2 were similar to those of FI with periods of 213 ± 100, 60 ± 46, and 28 ± 3.6 (SD) seconds. However, the CO2 spectral peak magnitudes were small, with an estimated maximal effect on CBF of (±) 2.5 ± 0.98, 1.5 ± 0.54, and 1.1 ± 0.31 (SD) percent. The frequencies of the blood pressure spectral peaks also were similar, with periods of 173 ± 81, 44 ± 8, and 26 ± 2.5 (SD) seconds. Their magnitudes were small, corresponding to variations in blood pressure of (±) 2.1 ± 0.55, 0.97 ± 0.25, and 0.72 ± 0.19 (SD) percent. Furthermore, coherence analysis showed no correlation between CO2 and FI, and only weak correlations at isolated frequencies between CO2 and velocity, blood pressure and velocity, or blood pressure and FI. The Kolmogorov-Smirnov test distinguished our data from white noise in most cases. Oscillations in vessel flow occur with significant magnitude at three distinct frequencies in normal subjects at rest and can be detected with a TCD-derived index. The presence of oscillations in blood velocity at similar frequencies but at lower magnitudes suggests that the vessel diameters oscillate in synchrony with flow. Observed variations in CO2 and blood pressure do not explain the flow oscillations. Ordinary TCD velocities severely underestimate these oscillations and so are not appropriate when small changes in flow are to be measured.
Blood flow information available from transcranial Doppler ultrasound is usually derived from velocity alone because no knowledge of vessel caliber is available. In cases such as vasospasm, where ...vessel size changes, the inference of flow from velocity becomes questionable. A computational technique was used to calculate a flow index and 2 vessel area indices based on the first and zero moments of the Doppler power spectrum. These indices were tested in a steady and pulsatile flow phantom using 6 different diameter elastic tubes. Changes in the flow index showed good agreement with changes in timed volume flow for different flow rates. The vessel caliber indices correctly predicted changes in area when different diameter tubes were examined. These indices may prove useful in clinical settings where the constancy of flow or vessel diameter between studies are in question.
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