NASA-CR-204564 Structures in ionospheric number density and velocity associated with polar cap ionization patches C )
Spectral characteristics of polar cap F region irregularities on large density gradients associated with polar ionization patches are studied using in situ measurements made by the Dynamics Explorer 2 (DE 2) spacecraft. The • 18 patches studied in this paper were identified by the algorithm introduced by Coley and Heelis [1995], and they were encountered during midnight-noon passes of the spacecraft. Density and velocity spectra associated with these a_tisunward convecting patches are analyzed in detail. Observations indicate the presence of structure on most patches regardless of the distance between the patch and the cusp where they are believed to develop. Existence of structure on both leading and trailing edges is established when such edges exist. Results, which show no large dependence of AN/N power on the sign of the edge gradient VN, do not allow the identification of leading and trailing edges of the patch. The AN/N is an increasing function of VN regardless of the sign of the gradient. The correlation between AN/N and AV is generally poor, but for a given intensity in AV, AN/N maximizes in regions of large gradients in N. There is evidence for the presence of unstructured patches that seem to coexist with unstructured horizontal velocities. Slightly smaller spectral indices for trailing edges support the presence of the E×B drift instability. Although this instability is found to be operating in some cases, results suggest that stirring may be a significant contributor to kilometer-size structures in the polar cap. C/) "D .//' "" "--"
Origin of density enhancements in the winter polar cap ionosphere
Coherent and incoherent ground-based radar measurements of the winter polar cap ionosphere at Thule and Sondrestrom, Greenland have established the existence of “patches” of enhanced ionization which drift across the polar cap in an antisunward, noon-midnight direction. Associated with these patches is strong radio scintillation activity which severely disrupts ground-to-satellite communication systems and interferes with the operation of space surveillance radar at high latitudes. Several recent studies have shown that the source of enhanced ionization is the sunlit subcusp ionosphere rather than production by precipitating energetic particles. However, the question of what causes the patchiness has not been addressed. We study this problem by solving the time-dependent plasma continuity equation including production by solar ultraviolet radiation, loss through charge exchange, and transport by diffusion and convection E×B drifts. Time and spatially varying, horizontal E×B drift patterns are imposed, and subsequent ionospheric responses are calculated to determine how enhanced plasma densities in the dark polar cap could result from extended transit of relevant flux tubes through regions of significant solar production. This would occur south of the cusp prior to convection as patches across the polar cap. It is found that a density enhancement in Nmax from 7×104 to 5×105 el/cm3 occurs at Thule when a time-varying convection pattern is included in the simulation. The patch of ionization is generated when an initial convection pattern characterized by an 80-kV cross-tail potential and a 12° polar cap radius is abruptly changed to a 100-kV cross-tail potential and a 15° polar cap radius. The horizontal extent of the patch is related to the length of time the new convection pattern remains “turned on.”
Study on essential drug use status and its influencing factors among cerebral infarction inpatients in county level hospitals of Anhui Province, China
Background and purpose Drug costs is one of the main components of hospitalization expenditure for cerebral infarction inpatients. In China, the National Essential Medicine System (NEMS) was created to relieve the heavy drug-cost burden for patients. The objective of this study was to investigate essential drug-use status and its influencing factors among cerebral infarction inpatients in county-level hospitals of Anhui province, China. Methods Three county-level hospitals were selected through a multi-stage cluster random sampling method. The hospitalization cost data of cerebral infarction inpatients in the three hospitals were extracted from the Anhui provincial information platform of the New Rural Cooperative Insurance System (NCMS), and whether the proportion of essential drug cost in the total drug cost reached the median value of 33.05% which was set as the evaluation index for essential drug-use status. Questionnaires for hospitals and physicians were designed and given to them to assess influencing factors. Results We retrieved the cost data of 2,189 inpatients from the NCMS platform and investigated 51 corresponding physicians in total. The drug costs accounted for 52.6% of the total hospitalization cost, and essential drug costs alone accounted for 37.0% of the total drug costs. The essential drug-cost proportion was high among physicians with a higher recognition degree on NEMS, older age, lower final academic degree, longer work experience and lower professional title. Married physicians and those with tight organizational affiliation also prescribed more essential drugs. Conclusions Increasing the proportion of essential drugs was an effective way to reduce the disease burden for cerebral infarction patients. Perfecting the NEMS, increasing government investment, reinforcing education and propaganda, and formulating relevant incentive and restrictive mechanisms were all effective ways to promote and increase the number of essential drug prescriptions written by physicians.