We report a net inward, up-gradient turbulent particle flux in a cylindrical plasma when collisional drift waves generate a sufficiently strong sheared azimuthal flow that drives positive (negative) density fluctuations up (down) the background density gradient, resulting in a steepening of the mean density gradient. The results show the existence of a saturation mechanism for drift-turbulence driven sheared flows that can cause up-gradient particle transport and density profile steepening.

We report the observation of a transport bifurcation that occurs by spontaneous self-organization of a drift-wave and shear flow system in a linear plasma device. As we increase the magnetic field above a threshold (BCr = 1200 G), a global transition occurs, with steepening of mean density and ion pressure profiles, onset of strong E × B shearing, a reduction of turbulence, and improved turbulent radial particle transport. An abrupt transition appears in the graph of turbulent particle flux versus density gradient. Hysteresis in the density gradient further confirms this transport bifurcation. The total Reynolds work on the flow sharply increases above threshold. This correlates with the increase of density steepness, which suggests the Reynolds stress-driven flow that plays an essential role in density steepening and transport bifurcation. A change in turbulence feature from drift waves (DWs) to a mix of DWs and ion temperature gradients also coincides with the transport bifurcation. Interesting phenomena related to the transport bifurcation are also reported; a local inward particle flux, the co-existence of ion and electron features, and a self-sustained axial flow absent momentum input.

Background: Drug and multidrug-resistant Plasmodium falciparum malaria has existed in Thailand for several decades. Furthermore, Thailand serves as a sentinel for drug-resistant malaria within the Greater Mekong sub-region. However, the drug resistance situation is highly dynamic, changing quickly over time. Here parasite in vitro drug sensitivity is reported for artemisinin derivatives, mefloquine, chloroquine and quinine, across Thailand. Methods. Blood was drawn from patients infected with P. falciparum in seven sentinel provinces along Thai international borders with Cambodia, Myanmar, Laos, and Malaysia. In vitro parasite sensitivity was tested using the World Health Organizations microtest (mark III) (between 1994 and 2002) and the histidine-rich protein-2 (HRP2)-based enzyme-linked immunosorbent assay (in 2010). Following World Health Organization protocol, at least 30 isolates were collected for each province and year represented in this study. Where possible, t-tests were used to test for significant differences. Results: There appears to be little variation across study sites with regard to parasite sensitivity to chloroquine. Quinine resistance appears to have been rising prior to 1997, but has subsequently decreased. Mefloquine sensitivity appears high across the provinces, especially along the north-western border with Myanmar and the eastern border with Cambodia. Finally, the data suggest that parasite sensitivity to artemisinin and its derivatives is significantly higher in provinces along the north-western border with Myanmar. Conclusions: Parasite sensitivity to anti-malarials in Thailand is highly variable over time and largely mirrors official drug use policy. The findings with regard to reduced sensitivity to artemisinin derivatives are supported by recent reports of reduced parasite clearance associated with artemisinin. This trend is alarming since artemisinin is considered the last defence against malaria. Continued surveillance in Thailand, along with increased collaboration and surveillance across the entire Greater Mekong sub-region, is clearly warranted. © 2012 Parker et al.; licensee BioMed Central Ltd.

In Myanmar, civil unrest and establishment of internally displaced persons (IDP) settlement along the Myanmar-China border have impacted malaria transmission. The growing IDP populations raise deep concerns about health impact on local communities. Microsatellite markers were used to examine the source and spreading patterns of Plasmodium falciparum between IDP settlement and surrounding villages in Myanmar along the China border. Genotypic structure of P. falciparum was compared over the past three years from the same area and the demographic history was inferred to determine the source of recent infections. In addition, we examined if border migration is a factor of P. falciparum infections in China by determining gene flow patterns across borders. Compared to local community, the IDP samples showed a reduced and consistently lower genetic diversity over the past three years. A strong signature of genetic bottleneck was detected in the IDP samples. P. falciparum infections from the border regions in China were genetically similar to Myanmar and parasite gene flow was not constrained by geographical distance. Reduced genetic diversity of P. falciparum suggested intense malaria control within the IDP settlement. Human movement was a key factor to the spread of malaria both locally in Myanmar and across the international border.

© 2015 Elsevier B.V. Deletion of the Plasmodium falciparum histidine-rich protein 2 (pfhrp2) gene may affect the performance of PfHRP2-based rapid diagnostic tests (RDTs). Here we investigated the genetic diversity of the pfhrp2 gene in clinical parasite isolates collected in recent years from the China-Myanmar border area. Deletion of pfhrp2 has been identified in 4 out of 97 parasite isolates. Sequencing of the pfhrp2 exon2 from 67 isolates revealed a high level of genetic diversity in pfhrp2, which is reflected in the presence of many repeat types and their variants, as well as variable copy numbers and different arrangements of these repeats in parasite isolates. In addition, we observed pfhrp3 deletion in three of the four parasites harboring pfhrp2 deletion, suggesting of double deletions of both genes in these three isolates. Analysis of two cases, which were P. falciparum-positive by microscopy and PCR but failed by two PfHRP2-based RDTs, did not find pfhrp2 deletion. Further correlational studies of pfhrp2 polymorphisms with detection sensitivity are needed to identify factors influencing the performance of RDTs in malaria-endemic areas.

Background: Malaria within the Greater Mekong sub-region is extremely heterogeneous. While China and Thailand have been relatively successful in controlling malaria, Myanmar continues to see high prevalence. Coupled with the recent emergence of artemisinin-resistant malaria along the Thai-Myanmar border, this makes Myanmar an important focus of malaria within the overall region. However, accurate epidemiological data from Myanmar have been lacking, in part because of ongoing and emerging conflicts between the government and various ethnic groups. Here the results are reported from a risk analysis of malaria slide positivity in a conflict zone along the China-Myanmar border. Methods. Surveys were conducted in 13 clinics and hospitals around Laiza City, Myanmar between April 2011 and October 2012. Demographic, occupational and educational information, as well as malaria infection history, were collected. Logistic models were used to assess risk factors for slide positivity. Results: Age patterns in Plasmodium vivax infections were younger than those with Plasmodium falciparum. Furthermore, males were more likely than females to have falciparum infections. Patients who reported having been infected with malaria during the previous year were much more likely to have a current vivax infection. During the second year of the study, falciparum infections among soldiers increased signficiantly. Conclusions: These results fill some knowledge gaps with regard to risk factors associated with malaria slide positivity in this conflict region of north-eastern Myanmar. Since epidemiological studies in this region have been rare or non-existent, studies such as the current are crucial for understanding the dynamic nature of malaria in this extremely heterogeneous epidemiological landscape. © 2013 Li et al.; licensee BioMed Central Ltd.

Copyright © 2015 by The American Society of Tropical Medicine and Hygiene. Artemisinin-based combination therapies (ACTs) are currently used as the first-line therapy for uncomplicated Plasmodium falciparum malaria. However, the recent emergence and/or spread of artemisinin resistance in parts of Greater Mekong Subregion (GMS) of southeast Asia requires close monitoring of the therapeutic efficacy of ACTs. This study was conducted from March 2012 to December 2013 in four clinics and seven villages along the China-Myanmar border. A total of 109 patients with uncomplicated falciparum malaria were treated with dihydroartemisinin-piperaquine (DP) and followed up on days 1, 2, 3, 7, 14, 21, 28, and 42 after treatment. A total of 71 patients (22 children and 49 adults) completed the 42-day follow-up. DP remained highly efficacious for treatment of uncomplicated falciparum malaria with an overall 42-day cure rate of 100%. The day 3 parasite-positive rate was 7.04% (5/71).Within 14 days of treatment, a total of 13 (18.31%) patients had detectable gametocytes and a large proportion of these were persistent from the first three days of treatment. The presence of gametocytes in patients through 14 days after DP treatment suggests that the incorporation of a single dose of primaquine for clearing gametocytemia should be considered for blocking parasite transmission.

We show that the degradation of fast-ion confinement in steady-state DIII-D discharges is quantitatively consistent with predictions based on the effects of multiple unstable Alfvén eigenmodes on beam-ion transport. Simulation and experiment show that increasing the radius where the magnetic safety factor has its minimum is effective in minimizing beam-ion transport. This is favorable for achieving high performance steady-state operation in DIII-D and future reactors. A comparison between the experiments and a critical gradient model, in which only equilibrium profiles were used to predict the most unstable modes, show that in a number of cases this model reproduces the measured neutron rate well.