Metal-Free Flat Lens Using Negative Refraction by Nonlinear Four-wave Mixing

A perfect lens with unlimited resolution has always posed a challenge to both theoretical and experimental physicists. Recent developments in optical meta-materials promise an attractive approach towards perfect lenses using negative refraction to overcome the diffraction limit, improving resolution. However, those artificially engineered meta-materials usually company by high losses from metals and are extremely difficult to fabricate. An alternative proposal using negative refraction by four-wave mixing has attracted much interests recently, though most of existing experiments still require metals and none of them has been implemented for an optical lens. Here we experimentally demonstrate a metal-free flat lens for the first time using negative refraction by degenerate four-wave mixing with a thin glass slide. We realize optical lensing effect utilizing a nonlinear refraction law, which may have potential applications in microscopy

Black-box Generalization of Machine Teaching

Hypothesis-pruning maximizes the hypothesis updates for active learning to find those desired unlabeled data. An inherent assumption is that this learning manner can derive those updates into the optimal hypothesis. However, its convergence may not be guaranteed well if those incremental updates are negative and disordered. In this paper, we introduce a black-box teaching hypothesis $h^\mathcal{T}$ employing a tighter slack term $\left(1+\mathcal{F}^{\mathcal{T}}(\widehat{h}_t)\right)\Delta_t$ to replace the typical $2\Delta_t$ for pruning. Theoretically, we prove that, under the guidance of this teaching hypothesis, the learner can converge into a tighter generalization error and label complexity bound than those non-educated learners who do not receive any guidance from a teacher:1) the generalization error upper bound can be reduced from $R(h^*)+4\Delta_{T-1}$ to approximately $R(h^{\mathcal{T}})+2\Delta_{T-1}$, and 2) the label complexity upper bound can be decreased from $4 \theta\left(TR(h^{*})+2O(\sqrt{T})\right)$ to approximately $2\theta\left(2TR(h^{\mathcal{T}})+3 O(\sqrt{T})\right)$. To be strict with our assumption, self-improvement of teaching is firstly proposed when $h^\mathcal{T}$ loosely approximates $h^*$. Against learning, we further consider two teaching scenarios: teaching a white-box and black-box learner. Experiments verify this idea and show better generalization performance than the fundamental active learning strategies, such as IWAL, IWAL-D, etc

Polysaccharides from the Chinese medicinal herb Achyranthes bidentata enhance anti-malarial immunity during Plasmodium yoelii 17XL infection in mice

<p>Abstract</p> <p>Background</p> <p>Clinical immunity to malaria in human populations is developed after repeated exposure to malaria. Regulation and balance of host immune responses may lead to optimal immunity against malaria parasite infection. Polysaccharides (ABPS) derived from the Chinese herb ox knee <it>Achyranthes bidentata </it>possess immuno-modulatory functions. The aim of this study is to use the rodent malaria model <it>Plasmodium yoelii </it>17XL (<it>P. y</it>17XL) to examine whether pretreatment with ABPS will modulate host immunity against malaria infection and improve the outcome of the disease.</p> <p>Methods</p> <p>To determine whether ABPS could modulate immunity against malaria, mice were pretreated with ABPS prior to blood-stage infection by <it>P. y</it>17XL. Host survival and parasitaemia were monitored daily. The effect of pretreatment on host immune responses was studied through the quantitation of cytokines, dendritic cell populations, and natural regulatory T cells (Treg).</p> <p>Results</p> <p>Pretreatment with ABPS prior to infection significantly extended the survival time of mice after <it>P. y</it>17XL infection. At three and five days post-infection, ABPS pretreated mice developed stronger Th1 immune responses against malaria infection with the number of F4/80⁺CD36⁺macrophages and levels of IFN-γ, TNF-α and nitric oxide being significantly higher than in the control group. More importantly, ABPS-treated mice developed more myeloid (CD11c⁺CD11b⁺) and plasmacytoid dendritic cells (CD11c⁺CD45R⁺/B220⁺) than control mice. ABPS pretreatment also resulted in modulated expression of MHC-II, CD86, and especially Toll-like receptor 9 by CD11c⁺dendritic cells. In comparison, pretreatment with ABPS did not alter the number of natural Treg or the production of the anti-inflammatory cytokine IL-10.</p> <p>Conclusion</p> <p>Pretreatment with the immuno-modulatory ABPS selectively enhanced Th1 immune responses to control the proliferation of malaria parasites, and prolonged the survival of mice during subsequent malaria infection.</p

Tryptophan-rich domains of Plasmodium falciparum SURFIN4.2 and Plasmodium vivax PvSTP2 interact with membrane skeleton of red blood cell

Additional file 1: Table S1. Primers for PCR amplification and plasmid construction

Malaria Elimination in the Greater Mekong Subregion: Challenges and Prospects

Malaria is a significant public health problem and impediment to socioeconomic development in countries of the Greater Mekong Subregion (GMS), which comprises Cambodia, China’s Yunnan Province, Lao People’s Democratic Republic, Myanmar, Thailand, and Vietnam. Over the past decade, intensified malaria control has greatly reduced the regional malaria burden. Driven by increasing political commitment, motivated by recent achievements in malaria control, and urged by the imminent threat of emerging artemisinin resistance, the GMS countries have endorsed a regional malaria elimination plan with a goal of eliminating malaria by 2030. However, this ambitious, but laudable, goal faces a daunting array of challenges and requires integrated strategies tailored to the region, which should be based on a mechanistic understanding of the human, parasite, and vector factors sustaining continued malaria transmission along international borders. Malaria epidemiology in the GMS is complex and rapidly evolving. Spatial heterogeneity requires targeted use of the limited resources. Border malaria accounts for continued malaria transmission and represents sources of parasite introduction through porous borders by highly mobile human populations. Asymptomatic infections constitute huge parasite reservoir requiring interventions in time and place to pave the way for malaria elimination. Of the two most predominant malaria parasites, Plasmodium falciparum and P. vivax, the prevalence of the latter is increasing in most member GMS countries. This parasite requires the use of 8-aminoquinoline drugs to prevent relapses from liver hypnozoites, but high prevalence of glucose-6-phosphate dehydrogenase deficiency in the endemic human populations makes it difficult to adopt this treatment regimen. The recent emergence of resistance to artemisinins and partner drugs in P. falciparum has raised both regional and global concerns, and elimination efforts are invariably prioritized against this parasite to avert spread. Moreover, the effectiveness of the two core vector control interventions—insecticide-treated nets and indoor residual spraying—has been declining due to insecticide resistance and increased outdoor biting activity of mosquito vectors. These technical challenges, though varying from country to country, require integrated approaches and better understanding of the malaria epidemiology enabling targeted control of the parasites and vectors. Understanding the mechanism and distribution of drug-resistant parasites will allow effective drug treatment and prevent, or slow down, the spread of drug resistance. Coordination among the GMS countries is essential to prevent parasite reintroduction across the international borders to achieve regional malaria elimination

Materials and fabrication of electrode scaffolds for deposition of MnO2 and their true performance in supercapacitors

MnO2 is a promising electrode material for high energy supercapacitors because of its large pseudo-capacitance. However, MnO2 suffers from low electronic conductivity and poor cation diffusivity, which results in poor utilization and limited rate performance of traditional MnO2 powder electrodes, obtained by pressing a mixed paste of MnO2 powder, conductive additive and polymer binder onto metallic current collectors. Developing binder-free MnO2 electrodes by loading nanoscale MnO2 deposits on pre-fabricated device-ready electrode scaffolds is an effective way to achieve both high power and energy performance. These electrode scaffolds, with interconnected skeletons and pore structures, will not only provide mechanical support and electron collection as traditional current collectors but also fast ion transfer tunnels, leading to high MnO2 utilization and rate performance. This review covers design strategies, materials and fabrication methods for the electrode scaffolds. Rational evaluation of the true performance of these electrodes is carried out, which clarifies that some of the electrodes with as-claimed exceptional performances lack potential in practical applications due to poor mass loading of MnO2 and large dead volume of inert scaffold materials/void spaces in the electrode structure. Possible ways to meet this challenge and bring MnO2 electrodes from laboratory studies to real-world applications are considered.National NSFCChina Scholarship CouncilNational Scholarship for Postgraduate Student

Occurrence and genetic characterization of Enterocytozoon bieneusi in pet dogs in Yunnan Province, China

Enterocytozoon bieneusi is the most common microsporidian species in humans and can affect over 200 animal species. Considering possible increasing risk of human E. bieneusi infection due to close contact with pet dogs and identification of zoonotic E. bieneusi genotypes, 589 fresh fecal specimens of pet dogs were collected from Yunnan Province, China to determine the occurrence of E. bieneusi, characterize dog-derived E. bieneusi isolates, and assess their zoonotic potential at the genotype level. Enterocytozoon bieneusi was identified and genotyped by PCR and sequencing of the internal transcribed spacer (ITS) region of the ribosomal RNA (rRNA) gene. Twenty-nine specimens (4.9%) were positive. A statistical difference was observed in occurrence rates of E. bieneusi in pet dogs among 11 sampling sites by Fisher’s exact test. Fifteen genotypes were identified and all of them phylogenetically belonged to zoonotic group 1, including four known genotypes (EbpC, D, Peru 8, and Henan-III) and 11 novel genotypes. Genotype Henan-III was reported in dogs for the first time. The finding of known genotypes found previously in humans and novel genotypes falling into zoonotic group 1 indicates that dogs may play a role in the transmission of E. bieneusi to humans in the investigated areas