Fermion Condensation and Gapped Domain Walls in Topological Orders

We propose the concept of fermion condensation in bosonic topological orders in two spatial dimensions. Fermion condensation can be realized as gapped domain walls between bosonic and fermionic topological orders, which are thought of as a real-space phase transitions from bosonic to fermionic topological orders. This generalizes the previous idea of understanding boson condensation as gapped domain walls between bosonic topological orders. We show that generic fermion condensation obeys a Hierarchy Principle by which it can be decomposed into a boson condensation followed by a minimal fermion condensation, which involves a single self-fermion that is its own anti-particle and has unit quantum dimension. We then develop the rules of minimal fermion condensation, which together with the known rules of boson condensation, provides a full set of rules of fermion condensation. Our studies point to an exact mapping between the Hilbert spaces of a bosonic topological order and a fermionic topological order that share a gapped domain wall.Comment: 20 pages, 2-colum

Frequency tuning behaviour of terahertz quantum cascade lasers revealed by a laser beating scheme

In the terahertz frequency range, the commercialized spectrometers, such as the Fourier transform infrared and time domain spectroscopies, show spectral resolutions between a hundred megahertz and a few gigahertz. Therefore, the high precision frequency tuning ability of terahertz lasers cannot be revealed by these traditional spectroscopic techniques. In this work, we demonstrate a laser beating experiment to investigate the frequency tuning characteristics of terahertz quantum cascade lasers (QCLs) induced by temperature or drive current. Two terahertz QCLs emitting around 4.2 THz with identical active regions and laser dimensions (150 μm wide and 6 mm long) are employed in the beating experiment. One laser is operated as a frequency comb and the other one is driven at a lower current to emit a single frequency. To measure the beating signal, the single mode laser is used as a fast detector (laser self-detection). The laser beating scheme allows the high precision measurement of the frequency tuning of the single mode terahertz QCL. The experimental results show that in the investigated temperature and current ranges, the frequency tuning coefficients of the terahertz QCL are 6.1 MHz/0.1 K (temperature tuning) and 2.7 MHz/mA (current tuning) that cannot be revealed by a traditional terahertz spectrometer. The laser beating technique shows potential abilities in high precision linewidth measurements of narrow absorption lines and multi-channel terahertz communications

Pesticide Research on Environmental and Human Exposure and Risks in Sub-Saharan Africa: A Systematic Literature Review

On the African continent, ongoing agriculture intensification is accompanied by the increasing use of pesticides, associated with environmental and public health concerns. Using a systematic literature review, we aimed to map current geographical research hotspots and gaps around environmental and public health risks research of agriculture pesticides in Sub-Saharan Africa (SSA). Studies were included that collected primary data on past and current-used agricultural pesticides and assessed their environmental occurrence, related knowledge, attitude and practice, human exposure, and environmental or public health risks between 2006 and 2021. We identified 391 articles covering 469 study sites in 37 countries in SSA. Five geographical research hotspots were identified: two in South Africa, two in East Africa, and one in West Africa. Despite its ban for agricultural use, organochlorine was the most studied pesticide group (60%; 86% of studies included DDT). Current-used pesticides in agriculture were studied in 54% of the study sites (including insecticides (92%), herbicides (44%), and fungicides (35%)). Environmental samples were collected in 67% of the studies (e.g., water, aquatic species, sediment, agricultural produce, and air). In 38% of the studies, human subjects were investigated. Only few studies had a longitudinal design or assessed pesticide’s environmental risks; human biomarkers; dose-response in human subjects, including children and women; and interventions to reduce pesticide exposure. We established a research database that can help stakeholders to address research gaps, foster research collaboration between environmental and health dimensions, and work towards sustainable and safe agriculture systems in SSA

Laurent inversion

There are well-understood methods, going back to Givental and Hori--Vafa, that to a Fano toric complete intersection X associate a Laurent polynomial f that corresponds to X under mirror symmetry. We describe a technique for inverting this process, constructing the toric complete intersection X directly from its Laurent polynomial mirror f. We use this technique to construct a new four-dimensional Fano manifold

Transdermal delivery of Chinese herbal medicine extract using dissolvable microneedles for hypertrophic scar treatment

Hypertrophic scars are unfavorable skin diseases characterized by excessive collagen deposition. Although systemic treatments exist in clinic to manage hypertrophic scars, they pose significant side effects and tend to lose efficacy over prolonged applications. Traditional Chinese medicine (TCM) offers as a promising candidate to treat pathological scars. A large number of TCMs have been studied to show anti-scarring effect, however, the natural barrier of the skin impedes their penetration, lowering its therapeutic efficacy. Herein, we reported the use of dissolvable hyaluronic acid (HA) microneedles (MNs) as a vehicle to aid the transdermal delivery of therapeutic agent, a model TCM called shikonin for the treatment of hypertrophic scars. Here, shikonin was mixed with HA to make MNs with adequate mechanical strength for skin penetration, making its dosage controllable during the fabrication process. The therapeutic effect of the shikonin HA MNs was studied in vitro using HSFs and then further verified with quantitative reverse transcriptase polymerase chain reaction. Our data suggest that the shikonin HA MNs significantly reduce the viability and proliferation of the HSFs and downregulate the fibrotic-related genes (i.e., TGFβ1, FAP-α and COL1A1). Furthermore, we observed a localized therapeutic effect of the shikonin HA MNs that is beneficial for site-specific treatment.Agency for Science, Technology and Research (A*STAR)Published versionChenjie Xu acknowledges the funding support from SingaporeAgency for Science, Technology and Research (A)STAR) Sci-ence and Engineering Research Council Additive Manufacturingfor Biological Materials (AMBM) program (A18A8b0059,Singapore), City University of Hong Kong (#9610472, China),General Research Fund (GRF) from University Grant Committeeof Hong Kong (UGC) Research Grant Council (RGC) (#9042951,China), and NSFC/RGC Joint Research Scheme (N_CityU118/20,China)

Switchable unidirectional emissions from hydrogel gratings with integrated carbon quantum dots

Abstract Directional emission of photoluminescence despite its incoherence is an attractive technique for light-emitting fields and nanophotonics. Optical metasurfaces provide a promising route for wavefront engineering at the subwavelength scale, enabling the feasibility of unidirectional emission. However, current directional emission strategies are mostly based on static metasurfaces, and it remains a challenge to achieve unidirectional emissions tuning with high performance. Here, we demonstrate quantum dots-hydrogel integrated gratings for actively switchable unidirectional emission with simultaneously a narrow divergence angle less than 1.5° and a large diffraction angle greater than 45°. We further demonstrate that the grating efficiency alteration leads to a more than 7-fold tuning of emission intensity at diffraction order due to the variation of hydrogel morphology subject to change in ambient humidity. Our proposed switchable emission strategy can promote technologies of active light-emitting devices for radiation control and optical imaging

Heritability of the HIV-1 reservoir size and decay under long-term suppressive ART

The HIV-1 reservoir is the major hurdle to curing HIV-1. However, the impact of the viral genome on the HIV-1 reservoir, i.e. its heritability, remains unknown. We investigate the heritability of the HIV-1 reservoir size and its long-term decay by analyzing the distribution of those traits on viral phylogenies from both partial-pol and viral near full-length genome sequences. We use a unique nationwide cohort of 610 well-characterized HIV-1 subtype-B infected individuals on suppressive ART for a median of 5.4 years. We find that a moderate but significant fraction of the HIV-1 reservoir size 1.5 years after the initiation of ART is explained by genetic factors. At the same time, we find more tentative evidence for the heritability of the long-term HIV-1 reservoir decay. Our findings indicate that viral genetic factors contribute to the HIV-1 reservoir size and hence the infecting HIV-1 strain may affect individual patients’ hurdle towards a cure.ISSN:2041-172

In situ generation of zinc oxide nanobushes on microneedles as antibacterial coating

This paper introduces a facile and scalable method to generate a layer of antibacterial coating on microneedles. The antibacterial coating (i.e., zinc oxide nanobushes) is generated on the surface of gold-coated polystyrene microneedles using the hydrothermal growth method. The antimicrobial property is examined using the agar diffusion test with both gram-positive and gram-negative bacteria.Agency for Science, Technology and Research (A*STAR)Accepted versionThe authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by Singapore A*STAR Biomedical Research Council (IAF-PP grant), NTU SUG (M4082114), and the Primary Research & Development Plan of Jiangsu Province of China (BE2016770). The thermal evaporator was supported by the Center for Disruptive Photonic Technologies of NTU