Microbes are unique creatures that adapt to varying lifestyles and environment resistance in extreme or adverse conditions. The genetic architecture of microbe may bear a significant signature not only in the sequences position, but also in the lifestyle to which it is adapted. It becomes a challenge for the society to find new chemical entities which can treat microbial infections. The present review aims to focus on account of important chemical moiety, that is, pyrimidine and its various derivatives as antimicrobial agents. In the current studies we represent more than 200 pyrimidines as antimicrobial agents with different mono-, di-, tri-, and tetrasubstituted classes along with in vitro antimicrobial activities of pyrimidines derivatives which can facilitate the development of more potent and effective antimicrobial agents.

IntroductionContemporary metropolitan areas are characterized by decentralized population and employment, extensive suburbanization, decline of the central business district (CBD), and the emergence of employment concentrations outside the CBD (eg Baerwald, 1982;

Patients evaluated for chest pain with angiographically normal coronary arteries are usually labelled syndrome X. A portion of these patients may not have a cardiac cause for their symptoms. The authors aimed to study a subset within this group who showed the phenomenon of slow coronary flow (SCF) as evidenced by a slow antegrade progression of the dye on the coronary arteriogram to see if this could be used as a marker of myocardial ischemia. This observational study included 207 patients being evaluated for suspected coronary artery disease and found to have normal coronary angiograms. SCF was seen in 49 of these patients (23.7%) while the remaining 158 (76.3%) had normal coronary flow (NCF), as detected by the corrected thrombosis in myocardial infarction (TIMI) frame count method (TIMI frame count more than 2 SD of normal). Forty of the 49 patients (82%) in the SCF group had classical angina as compared with only 51 of the 158 patients (32%) in the NCF group (p<0.01). Also, a definitively positive exercise test was observed more commonly in the SCF group than in the NCF group (71% vs 42%, p < 0.01). The authors conclude that SCF patients constitute a definite subset within the wide spectrum of syndrome X and that the phenomenon of SCF could be used as a marker for myocardial ischemia.

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This research examines the impact of accessibility on the growth of employment centres in the Los Angeles region between 1990 and 2000. There is extensive empirical documentation of polycentricity—the presence of multiple concentrations of employment—in large metropolitan areas. However, there is limited understanding of the determinants of growth of employment centres. It has long been held that transport investments influence urban structure, particularly freeways and airports. Using data on 48 employment centres, the effects are tested of various measures of accessibility on centre employment growth: highway accessibility, network accessibility and two measures of labour force accessibility. Access to airports is also tested. It is found that, after controlling for centre size, density, industry mix, location within the region and spatial amenities, labour force accessibility and network accessibility are significantly related to centre growth. It is concluded that accessibility continues to play an important role in urban spatial structure.

The existence and persistence of cities provide prima facie evidence of agglomeration economies, but do little to inform our understanding of the specific nature of forces that induce the concentration of economic activity, nor the spatial scale at which they occur. Though the theoretical literature on conceptualizes these forces without specific geographic scale, the empirical literature largely treats them as working mainly at the metropolitan level. We argue that agglomeration may work at different spatial scales. There is now extensive evidence that metropolitan areas are polycentric, with a significant portion of employment clustered in employment centers outside the CBD. This provides basic evidence of net agglomeration benefits at the sub-metropolitan level. We explore theories of agglomeration and consider how they may explain the presence, location, characteristics, and growth of employment centers. We illustrate the usefulness of exploring polycentricity with a case study of the Los Angeles region. Our understanding of agglomeration economies can be enriched by investigating the nature of employment centers and the forces that produce and sustain them. JEL Classification