A new kind of nitrogen-doped graphene/carbon nanotube nanocomposite can be synthesized by a facile hydrothermal process under mild conditions, which exhibits synergistically enhanced electrochemical activity for the oxygen reduction reaction. This research provides a new route to access a metal-free electrocatalyst with high activity under mild conditions.

Near-field communication (NFC) labeling technology has been recently used to endow smartphones with nonline-of-sight sensing functions to improve the environment, human health, and quality of life. For applications in detecting food spoilage, the development of a sensor with high enough sensitivity to act as a switch for an NFC tag remains a challenge. In this Letter, we developed a nanostructured conductive polymer-based gas sensor with high sensitivity of Δ R/ R = 225% toward 5 ppm ammonia NH and unprecedented sensitivities of 46% and 17% toward 5 ppm putrescine and cadaverine, respectively. The gas sensor plays a critical role as a sensitive switch in the circuit of the NFC tag and enables a smartphone to readout meat spoilage when the concentration of biogenic amines is over a preset threshold. We envision the broad potential use of such intelligent sensing for food status monitoring applications in daily life, storage and supply chains.

Background: The aim of this study was to analyze and summarize the clinical characteristics of elderly patients with coronavirus disease 2019 (COVID-19) and compare the differences of young-old patients (60–74 years old) and old-old patients (≥75 years old). Methods: In thisretrospective, multicenter study, the medical records of elderly patients who were diagnosed with COVID-19 in Hunan province, China, from January 21 to February 19, 2020 were reviewed. The characteristics of young-old patients and old-old patients were compared. Results: Of the 105 elderly patientsconfirmed withCOVID-19, 81.0% were young-old patients, and 19.0% were old-old patients; 54.3% of elderly patients were females. Overall, 69.5% of elderly patients had underlying diseases, and the most common comorbidities included hypertension (43.8%), diabetes (25.7%), and cardiac disease (16.2%). Of the elderly patients, 22.9% were severe and 10.5% were critical severe cases. On admission, the most frequent symptoms in elderly patients included fever (66.7%), cough (64.8%), and fatigue (33.3%). Lymphopenia (31.4%), increased D-dimer (38.1%), depressed albumin (36.2%), elevated lactate dehydrogenase (41.0%), and a high level of C-reactive protein (79.0%) were common among elderly patients with COVID-19. The median prothrombin time (PT) and the activated partial thromboplastin time (APTT) were longer in old-old patients than young-old patients (PT median 12.3 vs. 13.1 s, p = 0.007; APTT median 39.0 vs. 33.5 s, p = 0.045). Young-old patients showed fewer complications (14.1%) than old-old patients (40.0%; p = 0.0014) and fewer received invasive ventilator support (3.5 vs. 25.0%, p = 0.006). As of March 11, 2020, 85.7% of elderly patients had been discharged, 3 deaths had occurred, and 11.4% were still hospitalized. Conclusions: Elderly patients usually have chronic medical illness and are likely to have a severe or critically severe condition. They could show atypical symptoms without fever or cough and multiple organ dysfunction. Old-old patients tend to have more complications than young-old patients during hospitalization. Careful nursing, observation, and systemic treatment are very important in elderly patients.

Nanostructures on a plate! Single‐crystalline metal oxide nanostructures (see SEM images) have been synthesized on a large scale and at low cost on a wide range of substrates by directly heating the metal foils or metal‐coated substrates at low temperatures in air. Such a hotplate method could be potentially useful in the fabrication of nanomaterials for further fundamental research and industrial applications.

The fascinating two‐dimensional (2D) materials are being potentially applied in various fields from science to engineering benefitting from the charming physical and chemical properties on optics, electronics, and magnetism, compared with the bulk crystal, while piezotronics is a universal and pervasive phenomenon in the materials with broking center symmetry, promoting the new field and notable achievements of piezotronics in 2D materials with higher accuracy and sensitivity. For example, 20 parts per billion of the detecting limitations in NO2 sensor, 500 μm of spatial strain resolution in flexible devices, and 0.363 eV output voltage in nanogenerators. In this review, three categories of 2D piezotronics materials are first introduced ranging from organic to inorganic data, among which six types of 2D inorganic materials are emphasized based on the geometrical arrangement of different atoms. Then, the microscopic mechanism of carrier transport and separation in 2D piezotronic materials is highlighted, accompanied with the presentation of four measured methods. Subsequently, the developed applications of 2D piezotronics are discussed comprehensively including different kinds of sensors, piezo‐catalysis, nanogenerators and information storage. Ultimately, we suggest the challenges and provide the ideas for qualitative–quantitative research of microscopic mechanism and large‐scale integrated applications of 2D piezotronics.

Lei, MD have contributed equally to this work.Word count: 3166 All rights reserved. No reuse allowed without permission. the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. AbstractBackground: The clinical outcomes of COVID-19 patients in Hubei and other areas are different. We aim to investigate the epidemiological and clinical characteristics of patient with COVID-19 in Hunan which is adjacent to Hubei. Methods:In this double-center, observational study, we recruited all consecutive patients with laboratory confirmed COVID-19 from January 23 to February 14, 2020 in two designated hospitals in Hunan province, China. Epidemiological and clinical data from patients' electronic medical records were collected and compared between mild, moderate and severe/critical group in detail. Clinical outcomes were followed up to February 20, 2020. Findings: 291 patients with COVID-19 were categorized into mild group (10.0%), moderate group (72.8%) and severe/critical group (17.2%). The median age of all patients was 46 years (49.8% were male). 86.6% patients had an indirect exposure history. The proportion of patients that had been to Wuhan in severe/critical group (48.0% vs 17.2%, p=0.006) and moderate group (43.4% vs 17.2%, p=0.007) were higher than mild group. Fever (68.7%), cough (60.5%), and fatigue (31.6%) were common symptoms especially for severe and critical patients. Typical lung imaging finding were bilateral and unilateral ground glass opacity or consolidation. Leukopenia, lymphopenia and eosinopenia occurred in 36.1%, 22.7% and 50.2% patients respectively. Increased fibrinogen was detected in 45 of 58 (77.6%) patients with available results. 29 of 44 (65.9%) or 22 of 40 (55.0%) patients were positive in Mycoplasma pneumonia or Chlamydia pneumonia antibody test respectively.Compared with mild or moderate group, severe/critical group had a relative higher level of neutrophil, All rights reserved. No reuse allowed without permission. the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

No abstract

Segmentation of fetal left ventricle (LV) in echocardiographic sequences is important for further quantitative analysis of fetal cardiac function. However, image gross inhomogeneities and fetal random movements make the segmentation a challenging problem. In this paper, a dynamic convolutional neural networks (CNN) based on multiscale information and fine-tuning is proposed for fetal LV segmentation. The CNN is pretrained by amount of labeled training data. In the segmentation, the first frame of each echocardiographic sequence is delineated manually. The dynamic CNN is fine-tuned by deep tuning with the first frame and shallow tuning with the rest of frames, respectively, to adapt to the individual fetus. Additionally, to separate the connection region between LV and left atrium (LA), a matching approach, which consists of block matching and line matching, is used for mitral valve (MV) base points tracking. Advantages of our proposed method are compared with an active contour model (ACM), a dynamical appearance model (DAM), and a fixed multiscale CNN method. Experimental results in 51 echocardiographic sequences show that the segmentation results agree well with the ground truth, especially in the cases with leakage, blurry boundaries, and subject-to-subject variations. The CNN architecture can be simple, and the dynamic fine-tuning is efficient.