Beyond Scalar Treatment: A Causal Analysis of Hippocampal Atrophy on Behavioral Deficits in Alzheimer's Studies

Alzheimer's disease is a progressive form of dementia that results in problems with memory, thinking and behavior. It often starts with abnormal aggregation and deposition of beta-amyloid and tau, followed by neuronal damage such as atrophy of the hippocampi, and finally leads to behavioral deficits. Despite significant progress in finding biomarkers associated with behavioral deficits, the underlying causal mechanism remains largely unknown. Here we investigate whether and how hippocampal atrophy contributes to behavioral deficits based on a large-scale observational study conducted by the Alzheimer's Disease Neuroimaging Initiative (ADNI). As a key novelty, we use 2D representations of the hippocampi, which allows us to better understand atrophy associated with different subregions. It, however, introduces methodological challenges as existing causal inference methods are not well suited for exploiting structural information embedded in the 2D exposures. Moreover, our data contain more than 6 million clinical and genetic covariates, necessitating appropriate confounder selection methods. We hence develop a novel two-step causal inference approach tailored for our ADNI data application. Analysis results suggest that atrophy of CA1 and subiculum subregions may cause more severe behavioral deficits compared to CA2 and CA3 subregions. We further evaluate our method using simulations and provide theoretical guarantees

Integrated microwave acousto-optic frequency shifter on thin-film lithium niobate

Electrically driven acousto-optic devices that provide beam deflection and optical frequency shifting have broad applications from pulse synthesis to heterodyne detection. Commercially available acousto-optic modulators are based on bulk materials and consume Watts of radio frequency power. Here, we demonstrate an integrated 3-GHz acousto-optic frequency shifter on thin-film lithium niobate, featuring a carrier suppression over 30 dB. Further, we demonstrate a gigahertz-spaced optical frequency comb featuring more than 200 lines over a 0.6-THz optical bandwidth by recirculating the light in an active frequency shifting loop. Our integrated acousto-optic platform leads to the development of on-chip optical routing, isolation, and microwave signal processing

Positive and unlabeled learning for user behavior analysis based on mobile internet traffic data

With the rapid development of wireless communication and mobile Internet, mobile phone becomes ubiquitous and functions as a versatile and smart system, on which people frequently interact with various mobile applications (Apps). Understanding human behaviors using mobile phone is significant for mobile system developers, for human-centered system optimization and better service provisioning. In this paper, we focus on mobile user behavior analysis and prediction based on mobile Internet traffic data. Real traffic flow data is collected from the public network of Internet Service Providers (ISPs), by high-performance network traffic monitors.We construct User-App bipartite network to represent the traffic interaction pattern between users and App servers. After mining the explicit and implicit features from User-App bipartite network, we propose two positive and unlabeled learning (PU learning) methods, including Spy-based PU learning and K-means-based PU learning, for App usage prediction and mobile video traffic identification. We firstly use the traffic flow data of QQ, a very famous messaging and social media application possessing high market share in China, as the experimental dataset for App usage prediction task. Then we use the traffic flow data from six popular Apps, including video intensive Apps (Youku, Baofeng, LeTV, Tudou) and other Apps (Meituan, Apple), as the experimental dataset for mobile video traffic identification task. Experimental results show that our proposed PU learning methods perform well in both tasks

Microwave-to-optical conversion using lithium niobate thin-film acoustic resonators

Acoustic or mechanical resonators have emerged as a promising means to mediate efficient microwave-to-optical conversion. Here, we demonstrate conversion of microwaves up to 4.5 GHz in frequency to 1500 nm wavelength light using optomechanical interactions on suspended thin-film lithium niobate. Our method uses an interdigital transducer that drives a freestanding 100 μm-long thin-film acoustic resonator to modulate light traveling in a Mach–Zehnder interferometer or racetrack cavity. The strong microwave-to-acoustic coupling offered by the transducer in conjunction with the strong photoelastic, piezoelectric, and electro-optic effects of lithium niobate allows us to achieve a half-wave voltage of Vπ = 4.6 V and Vπ = 0.77 V for the Mach–Zehnder interferometer and racetrack resonator, respectively. The acousto-optic racetrack cavity exhibits an optomechanical single-photon coupling strength of 1.1 kHz. To highlight the versatility of our system, we also demonstrate a microwave photonic link with unitary gain, which refers to a 0 dB microwave power transmission over an optical channel. Our integrated nanophotonic platform, which leverages the compelling properties of lithium niobate, could help enable efficient conversion between microwave and optical fields

Integrated microwave acousto-optic frequency shifter on thin-film lithium niobate

Electrically driven acousto-optic devices that provide beam deflection and optical frequency shifting have broad applications from pulse synthesis to heterodyne detection. Commercially available acousto-optic modulators are based on bulk materials and consume Watts of radio frequency power. Here, we demonstrate an integrated 3-GHz acousto-optic frequency shifter on thin-film lithium niobate, featuring a carrier suppression over 30 dB. Further, we demonstrate a gigahertz-spaced optical frequency comb featuring more than 200 lines over a 0.6-THz optical bandwidth by recirculating the light in an active frequency shifting loop. Our integrated acousto-optic platform leads to the development of on-chip optical routing, isolation, and microwave signal processing

Abiotic factors controlling bioavailability and bioaccessibility of polycyclic aromatic hydrocarbons in soil:Putting together a bigger picture

The bioavailability and bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in soil underpin the risk assessment of contaminated land with these contaminants. Despite a significant volume of research conducted in the past few decades, comprehensive understanding of the factors controlling the behaviour of soil PAHs and a set of descriptive soil parameters to explain variations in PAH bioavailability and bioaccessibility are still lacking. This review focuses on the role of source materials on bioavailability and bioaccessibility of soil PAHs, which is often overlooked, along with other abiotic factors including contaminant concentration and mixture, soil composition and properties, as well as environmental factors. It also takes into consideration the implications of different types of risk assessment (ecological and human health) on bioavailability and bioaccessibility of PAHs in soil. We recommend that future research should (1) account for the effects of source materials on bioavailability and bioaccessibility of soil PAHs; (2) adopt non-disruptive methods to analyse soil components controlling PAH sequestration; (3) integrate both natural organic matter (NOM) and xenobiotic organic matter (XOM) while evaluating the influences of soil organic matter (SOM) on the behaviour of PAHs; and (4) consider the dissimilar desorption scenarios in ecological risk assessment and human health risk assessment while assessing PAH bioavailability and bioaccessibility

Buffered cyclodextrin extraction of -phenanthrene from black carbon amended soil

The presence of black carbon (BC) in soil drastically reduced the mineralisation of 14 C -phenanthrene and its extractability by hydroxypropyl- β -cyclodextrin (HPCD) extractions. This study also tested the effects of pH on the HPCD extraction of 14 C -phenanthrene in soils with BC. Extractions using 60 mM HPCD solutions prepared in deionised water (pH 5.89) and phosphate buffers (pH 7 and 8) were conducted on 14 C -phenanthrene-spiked soils amended with three different types of BC (1% dry weight) after 1, 25, and 50 d of ageing. Biodegradation assays using a Pseudomonas sp. strain were also carried out. Results showed that after 1 and 25 d, HPCD at pH 7 extracted significantly more 14 C -phenanthrene ( p 0.05 ) amounts of phenanthrene compared to the un-buffered solution. At 50 d, HPCD at pH 8 generally extracted more 14 C -phenanthrene from all treatments. It was proposed that higher pH promoted the dissolution of soil organic matter (SOM), leading to a greater solubility of phenanthrene in the solvent phase and enhancing the extractive capability of HPCD solutions. Although correlations between extractability and biodegradability of 14 C -phenanthrene in BC-amended soils were poor, increasing pH was demonstrated a viable approach to enhancing HPCD extractive capability for the 14 C -PAH from soil with BC