Size Dependence of Metal-Insulator Transition in Stoichiometric Fe3O4 Nanocrystals

Magnetite (Fe3O4) is one of the most actively studied materials with a famous metal-insulator transition (MIT), so-called the Verwey transition at around 123 K. Despite the recent progress in synthesis and characterization of Fe3O4 nanocrystals (NCs), it is still an open question how the Verwey transition changes on a nanometer scale. We herein report the systematic studies on size dependence of the Verwey transition of stoichiometric Fe3O4 NCs. We have successfully synthesized stoichiometric and uniform-sized Fe3O4 NCs with sizes ranging from 5 to 100 nm. These stoichiometric Fe3O4 NCs show the Verwey transition when they are characterized by conductance, magnetization, cryo-XRD, and heat capacity measurements. The Verwey transition is weakly size-dependent and becomes suppressed in NCs smaller than 20 nm before disappearing completely for less than 6 nm, which is a clear, yet highly interesting indication of a size effect of this well-known phenomena. Our current work will shed new light on this ages-old problem of Verwey transition.Comment: 18 pages, 4 figures, Nano Letters (accepted

What impact might the economic crisis have on HIV epidemics in Southeast Asia?

Objective: To evaluate the potential impact of the current global economic crisis (GEC) on the spread of HIV. Design: To evaluate the impact of the economic downturn we studied two distinct HIV epidemics in Southeast Asia: the generalized epidemic in Cambodia where incidence is declining and the epidemic in Papua New Guinea (PNG) which is in an expansion phase. Methods: Major HIV-related risk factors that may change due to the GEC were identified and a dynamic mathematical transmission model was developed and used to forecast HIV prevalence, diagnoses, and incidence in Cambodia and PNG over the next 3 years. Results: In Cambodia, the total numbers of HIV diagnoses are not expected to be largely affected. However, an estimated increase of up to 10% in incident cases of HIV, due to potential changes in behavior, may not be observed by the surveillance system. In PNG, HIV incidence and diagnoses could be more affected by the GEC, resulting in respective increases of up to 17% and 11% over the next 3 years. Decreases in VCT and education programs are the factors that may be of greatest concern in both settings. A reduction in the rollout of antiretroviral therapy could increase the number of AIDS-related deaths (by up to 7.5% after 3 years). Conclusions: The GEC is likely to have a modest impact on HIV epidemics. However, there are plausible conditions under which the economic downturns can noticeably influence epidemic trends. This study highlights the high importance of maintaining funding for HIV programs

Australia on track to achieve WHO HCV elimination targets following rapid initial DAA treatment uptake : A modelling study

Subsidized direct-acting antiviral (DAA) treatment recently became available to all adults living with chronic hepatitis C virus (HCV) in Australia. Based on rapid uptake (32 600 people initiated DAA in 2016), we estimated the impact on HCV epidemiology and mortality in Australia and determined if Australia can meet the WHO HCV elimination targets by 2030. Using a mathematical model, we simulated pessimistic, intermediate and optimistic DAA treatment scenarios in Australia over 2016-2030. We assumed treatment and testing rates were initially higher for advanced fibrosis and the same across HCV transmission risk level sub-populations. We also assumed constant testing rates after 2016. We compared the results to the 2015 level and a counterfactual (IFN-based) scenario. During 2016-2030, we estimated an intermediate DAA treatment scenario (2016, 32 600 treated; 2017, 21 370 treated; 2018 17 100 treated; 2019 and beyond, 13 680 treated each year) would avert 40 420 new HCV infections, 13 260 liver-related deaths (15 320 in viraemic; −2060 in cured) and 10 730 HCC cases, equating to a 53%, 63% and 75% reduction, respectively, compared to the IFN-based scenario. The model also estimated that Australia will meet the WHO targets of incidence and treatment by 2028. Time to a 65% reduction in liver-related mortality varied considerably between HCV viraemic only cases (2026) and all cases (2047). Based on a feasible DAA treatment scenario incorporating declining uptake, Australia should meet key WHO HCV elimination targets in 10 to15 years. The pre-DAA escalation in those with advanced liver disease makes the achievement of the liver-related mortality target difficult

Therapeutic Cell Protective Role of Histochrome under Oxidative Stress in Human Cardiac Progenitor Cells

Cardiac progenitor cells (CPCs) are resident stem cells present in a small portion of ischemic hearts and function in repairing the damaged heart tissue. Intense oxidative stress impairs cell metabolism thereby decreasing cell viability. Protecting CPCs from undergoing cellular apoptosis during oxidative stress is crucial in optimizing CPC-based therapy. Histochrome (sodium salt of echinochrome A—a common sea urchin pigment) is an antioxidant drug that has been clinically used as a pharmacologic agent for ischemia/reperfusion injury in Russia. However, the mechanistic effect of histochrome on CPCs has never been reported. We investigated the protective effect of histochrome pretreatment on human CPCs (hCPCs) against hydrogen peroxide (H2O2)-induced oxidative stress. Annexin V/7-aminoactinomycin D (7-AAD) assay revealed that histochrome-treated CPCs showed significant protective effects against H2O2-induced cell death. The anti-apoptotic proteins B-cell lymphoma 2 (Bcl-2) and Bcl-xL were significantly upregulated, whereas the pro-apoptotic proteins BCL2-associated X (Bax), H2O2-induced cleaved caspase-3, and the DNA damage marker, phosphorylated histone (γH2A.X) foci, were significantly downregulated upon histochrome treatment of hCPCs in vitro. Further, prolonged incubation with histochrome alleviated the replicative cellular senescence of hCPCs. In conclusion, we report the protective effect of histochrome against oxidative stress and present the use of a potent and bio-safe cell priming agent as a potential therapeutic strategy in patient-derived hCPCs to treat heart disease

Sensitivity of predatory bacteria to different surfactants and their application to check bacterial predation

We evaluated the toxicity of surfactants against different predatory bacteria. Tests with Bdellovibrio bacteriovorus HD100 and SDS, an anionic surfactant, showed the predator was very sensitive; 0.02% SDS completely killed the predatory population (7-log loss; < 10 PFU/ml remaining) both when free-swimming or within the bdelloplast, i.e., intraperiplasmic. Similar results were also observed with B. bacteriovorus 109J and Peredibacter starrii. In contrast, none of the prey (E. coli, Klebsiella pneumoniae, Acinetobacter baumannii, or Pseudomonas sp. DSM 50906) viabilities were negatively affected by SDS. Triton X-100, a nonionic surfactant, was slightly less toxic towards B. bacteriovorus HD100 (viability loss of only 4-log), while two cationic surfactants, i.e., benzalkonium chloride (BZC) and cetyltrimethylammonium bromide (CTAB), were toxic towards both the predator and prey. Based on the above findings, we tested the potential use of SDS as a means to control predation. Addition of 0.02% SDS immediately halted predation based upon the prey bioluminescence, which leveled off and remained steady. This was confirmed using the predator viabilities; no predators were found in any of the samples where SDS was added. Consequently, low concentrations of SDS can be used as a simple means to control B. bacteriovorus HD100 activities

Global change in hepatitis C virus prevalence and cascade of care between 2015 and 2020: a modelling study

Background Since the release of the first global hepatitis elimination targets in 2016, and until the COVID-19 pandemic started in early 2020, many countries and territories were making progress toward hepatitis C virus (HCV) elimination. This study aims to evaluate HCV burden in 2020, and forecast HCV burden by 2030 given current trends. Methods This analysis includes a literature review, Delphi process, and mathematical modelling to estimate HCV prevalence (viraemic infection, defined as HCV RNA-positive cases) and the cascade of care among people of all ages (age ≥0 years from birth) for the period between Jan 1, 2015, and Dec 31, 2030. Epidemiological data were collected from published sources and grey literature (including government reports and personal communications) and were validated among country and territory experts. A Markov model was used to forecast disease burden and cascade of care from 1950 to 2050 for countries and territories with data. Model outcomes were extracted from 2015 to 2030 to calculate population-weighted regional averages, which were used for countries or territories without data. Regional and global estimates of HCV prevalence, cascade of care, and disease burden were calculated based on 235 countries and territories. Findings Models were built for 110 countries or territories: 83 were approved by local experts and 27 were based on published data alone. Using data from these models, plus population-weighted regional averages for countries and territories without models (n=125), we estimated a global prevalence of viraemic HCV infection of 0·7% (95% UI 0·7–0·9), corresponding to 56·8 million (95% UI 55·2–67·8) infections, on Jan 1, 2020. This number represents a decrease of 6·8 million viraemic infections from a 2015 (beginning of year) prevalence estimate of 63·6 million (61·8–75·8) infections (0·9% [0·8–1·0] prevalence). By the end of 2020, an estimated 12·9 million (12·5–15·4) people were living with a diagnosed viraemic infection. In 2020, an estimated 641000 (623000–765000) patients initiated treatment. Interpretation At the beginning of 2020, there were an estimated 56·8 million viraemic HCV infections globally. Although this number represents a decrease from 2015, our forecasts suggest we are not currently on track to achieve global elimination targets by 2030. As countries recover from COVID-19, these findings can help refocus efforts aimed at HCV elimination