Aortic flow after valve sparing root replacement with or without neosinuses reconstruction

Objectives

This study applied advanced 4-dimensional flow magnetic resonance imaging processing to assess differences in aortic flow dynamics after valve sparing root replacement, with and without reconstruction of the Valsalva sinuses.

The effectiveness of a classroom-based phonological awareness program for 4–5-year-olds

Purpose: Numerous studies have reported a robust relationship between early phonological awareness (PA) and subsequent reading achievement, in addition to the critical role of the alphabetic principle in predicting and supporting later reading and spelling development. Given this association, there has been an increasing push to teach these skills to young children prior to word level reading and spelling instruction. This study evaluated the effectiveness of the Cracking the Code (CtC) program with students aged 3;8–5;4. CtC is a teacher-implemented program, designed to explicitly target PA skills and alphabet knowledge.

Method: A pre-test post-test group design was used to evaluate the effectiveness of the program. Four schools in metropolitan Western Australia were randomly assigned to either the control or experimental condition within a parallel groups design. The control group participated in an alternative program matched for duration and frequency, targeting semantics and grammar.

Result: The children in the experimental condition improved significantly more in PA, alphabet knowledge and non-word reading, and spelling after intervention than the control group.

Conclusion: These findings demonstrate that classroom-based, teacher-delivered PA and alphabet knowledge instruction can be effective for 3;8–5;4 year-olds.     

Early signal from the hippocampus for memory encoding

The mediotemporal lobe (MTL), including the hippocampus, is involved in all stages of episodic memory including memory encoding, consolidation, and retrieval. However, the exact timing of the hippocampus' involvement immediately after stimulus encounter remains unclear. In this study, we used high‐density 156‐channel electroencephalography to study the processing of entirely new stimuli, which had to be encoded, in comparison to highly overlearned stimuli. Sixteen healthy subjects performed a continuous recognition task with meaningful pictures repeated up to four consecutive times. Waveform and topographic cluster analyses of event‐related potentials revealed that new items, in comparison to repetitions, were processed significantly differently at 220–300 ms. Source estimation localized activation for processing new stimuli in the right MTL. Our study demonstrates the occurrence of a transient signal from the MTL in response to new information already at 200–300 ms poststimulus onset, which presumably reflects encoding as an initial step toward memory consolidation.     

北京与银川两家医院耐碳青霉烯类肠杆菌科细菌的流行特征研究#br#

目的 调查研究北京与银川两家医院耐碳青霉烯类肠杆菌(carbapenem-resistance Enterobacteriaceae, CRE)的流行病学特征，为CRE的临床诊治及其传播控制提供依据。方法 收集2008年1月至2017年12月间北京地区解放军302医院及银川地区宁夏医科大学总医院的临床标本中分离的CRE，分析其流行趋势、标本来源、病原特点及基因型组成，探讨CRE的流行病学特征。结果 两地区10年间分离鉴定出266株CRE，呈上升趋势，北京地区CRE检出率由2008年为0.45%上升到2017年的5.84%；银川地区CRE检出率由2008年的0.26%上升到2017年的3.1%。CRE感染患者以男性为主(159例，59.77%)，主要来自重症监护病房(intensive care unit，ICU)70例(26.31%)。北京与银川两家医院分离出CRE的主要标本为痰液(29.4%与26.3%)，血液(18.4%与6.5%)和尿液(10.5%与19.7%)，血液和尿液标本占比差异显著(P=0.015和0.045)。北京与银川两家医院CRE菌株以克雷伯菌属(66.32%和44.74%)、埃希菌属(20.00%和9.21%)及肠杆菌属(7.89%和36.84%)为主，差异均具有统计学意义(比较P值分别为0.0012、0.0340和0)。266株CRE总体对碳青霉烯类和头孢类抗生素的耐药率较高，对其他类抗生素包括磷霉素和左氧氟沙星的耐药率达到80%以上，对阿米卡星的耐药率近60%；对头孢他啶/阿维巴坦的耐药率为42.86%，耐药率较低的包括替加环素(4.51%)和多黏菌素B(4.14%)；北京地区CRE对阿米卡星和左氧氟沙星的耐药率显著高于银川地区。北京地区的blaKPC在克雷伯菌、埃希菌属和肠杆菌属中均占绝对优势(93.75%、61.9%和80%)，而blaNDM仅在埃希菌属中检测到；银川地区均以blaNDM基因为主，三个菌属中占比分别为36%、74%和85.71%，两地碳青霉烯酶耐药基因分布差异明显(P=0)。结论 北京与银川两地区的CRE菌株流行呈增长趋势，在标本来源、病原特点、碳青霉烯酶耐药基因分布等方面特征鲜明，临床应根据本地区的CRE流行特点采取针对性治疗。     

Immunogenicity generated by mRNA vaccine encoding VZV gE antigen is comparable to adjuvanted subunit vaccine and better than live attenuated vaccine in nonhuman primates

Shingles is a painful, blistering rash caused by reactivation of latent varicella-zoster virus (VZV) and most frequently occurs in elderly and immunocompromised individuals. Currently, two approved vaccines for the prevention of shingles are on the market, a live attenuated virus vaccine ZOSTAVAX® (Merck & Co., Inc., Kenilworth, NJ, USA) and an AS01_B adjuvanted subunit protein vaccine Shingrix™ (Glaxo Smith Kline, Rockville, MD, USA). Human clinical immunogenicity and vaccine efficacy data is available for these two benchmark vaccines, offering a unique opportunity for comparative analyses with novel vaccine platforms and animal model translatability studies.The studies presented here utilized non-human primates (NHP) to evaluate humoral and cellular immune response by three vaccine modalities: the new platform of lipid nanoparticle (LNP) formulated mRNA encoding VZV gE antigen (VZV gE mRNA/LNP) as compared with well-established platforms of live attenuated VZV (VZV LAV) and adjuvanted VZV gE subunit protein (VZV gE protein/adjuvant). The magnitude of response to vaccination with a single 100–200 μg mRNA dose or two 50 μg mRNA doses of VZV gE mRNA/LNP were comparable to two 50 μg protein doses of VZV gE protein/adjuvant, suggesting the VZV gE mRNA/LNP platform has the potential to elicit a robust immune response, and both modalities generated markedly higher responses than VZV LAV. Additionally, the slopes of decay for VZV-specific antibody titers were roughly similar across all three vaccines, indicating the magnitude of peak immunogenicity was the driving force in determining immune response longevity. Finally, vaccine-induced immunogenicity with VZV LAV and VZV gE protein/adjuvant in NHP closely resembled human clinical trials immune response data for ZOSTAVAX® and Shingrix™, helping to validate NHP as an appropriate preclinical model for evaluating these vaccines.     

A Bipolar-Bisection Piecewise Encoding Scheme for Multi-Source Reverse Time Migration

Conventional shot-record reverse time migration (RTM) suffers from a high computational burden when dealing with massive data. The computational cost of RTM can be reduced by shot-encoding techniques, and plane-wave encoding is a commonly used and effective shot-encoding scheme. However, plane-wave encoding requires long time padding to avoid information loss, which decreases the efficiency of the time-domain wavefield extrapolator, and the time padding becomes longer with the increasing distance between multiple sources. The piecewise plane-wave encoding scheme cuts multiple sources into several segments prior to implementing plane-wave encoding, hence reduces the time padding, but brings new crosstalk due to the mutual interference between shots in different source segments. We suppress the crosstalk artifacts by a new bipolar-bisection amplitude encoding method, in which half of the encoding array of each migration is different from that of any other migrations to reduce the number of crosstalk terms with as few migrations as possible. We embed the bipolar-bisection method into piecewise plane-wave encoding. Compared with plane-wave encoding, the proposed scheme requires considerably shorter time padding and thus works more efficiently and can generate a qualified imaging result. The feasibility of the proposed method is tested on the 2D SEG/EAGE salt model and the Marmousi model.     

Robust arterial transit time and cerebral blood flow estimation using combined acquisition of Hadamard‐encoded multi‐delay and long‐labeled long‐delay pseudo‐continuous arterial spin labeling: a simulation and in vivo study

Arterial transit time (ATT) prolongation causes an error of cerebral blood flow (CBF) measurement during arterial spin labeling (ASL). To improve the accuracy of ATT and CBF in patients with prolonged ATT, we propose a robust ATT and CBF estimation method for clinical practice. The proposed method consists of a three‐delay Hadamard‐encoded pseudo‐continuous ASL (H‐pCASL) with an additional‐encoding and single‐delay with long‐labeled long‐delay (1dLLLD) acquisition. The additional‐encoding allows for the reconstruction of a single‐delay image with long‐labeled short‐delay (1dLLSD) in addition to the normal Hadamard sub‐bolus images. Five different images (normal Hadamard 3 delay, 1dLLSD, 1dLLLD) were reconstructed to calculate ATT and CBF. A Monte Carlo simulation and an in vivo study were performed to access the accuracy of the proposed method in comparison to normal 7‐delay (7d) H‐pCASL with equally divided sub‐bolus labeling duration (LD). The simulation showed that the accuracy of CBF is strongly affected by ATT. It was also demonstrated that underestimation of ATT and CBF by 7d H‐pCASL was higher with longer ATT than with the proposed method. Consistent with the simulation, the 7d H‐pCASL significantly underestimated the ATT compared to that of the proposed method. This underestimation was evident in the distal anterior cerebral artery (ACA; P = 0.0394) and the distal posterior cerebral artery (PCA; 2 P = 0.0255). Similar to the ATT, the CBF was underestimated with 7d H‐pCASL in the distal ACA (P = 0.0099), distal middle cerebral artery (P = 0.0109), and distal PCA (P = 0.0319) compared to the proposed method. Improving the SNR of each delay image (even though the number of delays is small) is crucial for ATT estimation. This is opposed to acquiring many delays with short LD. The proposed method confers accurate ATT and CBF estimation within a practical acquisition time in a clinical setting.     

Motion‐compensated b‐tensor encoding for in vivo cardiac diffusion‐weighted imaging

Motion is a major confound in diffusion‐weighted imaging (DWI) in the body, and it is a common cause of image artefacts. The effects are particularly severe in cardiac applications, due to the nonrigid cyclical deformation of the myocardium. Spin echo‐based DWI commonly employs gradient moment‐nulling techniques to desensitise the acquisition to velocity and acceleration, ie, nulling gradient moments up to the 2nd order (M2‐nulled). However, current M2‐nulled DWI scans are limited to encode diffusion along a single direction at a time. We propose a method for designing b‐tensors of arbitrary shapes, including planar, spherical, prolate and oblate tensors, while nulling gradient moments up to the 2nd order and beyond. The design strategy comprises initialising the diffusion encoding gradients in two encoding blocks about the refocusing pulse, followed by appropriate scaling and rotation, which further enables nulling undesired effects of concomitant gradients. Proof‐of‐concept assessment of in vivo mean diffusivity (MD) was performed using linear and spherical tensor encoding (LTE and STE, respectively) in the hearts of five healthy volunteers. The results of the M2‐nulled STE showed that (a) the sequence was robust to cardiac motion, and (b) MD was higher than that acquired using standard M2‐nulled LTE, where diffusion‐weighting was applied in three orthogonal directions, which may be attributed to the presence of restricted diffusion and microscopic diffusion anisotropy. Provided adequate signal‐to‐noise ratio, STE could significantly shorten estimation of MD compared with the conventional LTE approach. Importantly, our theoretical analysis and the proposed gradient waveform design may be useful in microstructure imaging beyond diffusion tensor imaging where the effects of motion must be suppressed.     

Identification of two abundant Aerococcus urinae cell wall-anchored proteins

Aerococcus urinae is an emerging pathogen that causes urinary tract infections, bacteremia and infective endocarditis. The mechanisms through which A. urinae cause infection are largely unknown. The aims of this study were to describe the surface proteome of A. urinae and to analyse A. urinae genomes in search for genes encoding surface proteins. Two proteins, denoted Aerococcal surface protein (Asp) 1 and 2, were through the use of mass spectrometry based proteomics found to quantitatively dominate the aerococcal surface. The presence of these proteins on the surface was also shown using ELISA with serum from rabbits immunized with the recombinant Asp. These proteins had a signal sequence in the amino-terminal end and a cell wall-sorting region in the carboxy-terminal end, which contained an LPATG-motif, a hydrophobic domain and a positively charged tail. Twenty-three additional A. urinae genomes were sequenced using Illumina HiSeq technology. Six different variants of asp genes were found (denoted asp1-6). All isolates had either one or two of these asp-genes located in a conserved locus, designated Locus encoding Aerococcal Surface Proteins (LASP). The 25 genomes had in median 13 genes encoding LPXTG-proteins (range 6–24). For other Gram-positive bacteria, cell wall-anchored surface proteins with an LPXTG-motif play a key role for virulence. Thus, it will be of great interest to explore the function of the Asp proteins of A. urinae to establish a better understanding of the molecular mechanisms by which A. urinae cause disease.     

Effects of native language experience on Mandarin lexical tone processing in proficient second language learners

Learning the acoustic and phonological information in lexical tones is significant for learners of tonal languages. Although there is a wealth of knowledge from studies of second language (L2) tone learning, it remains unclear how L2 learners process acoustic versus phonological information differently depending on whether their first language (L1) is a tonal language. In the present study, we first examined proficient L2 learners of Mandarin with tonal and nontonal L1 in a behavioral experiment (identifying a Mandarin tonal continuum) to construct tonal contrasts that could differentiate the phonological from the acoustic information in Mandarin lexical tones for the L2 learners. We then conducted an ERP experiment to investigate these learners’ automatic processing of acoustic and phonological information in Mandarin lexical tones by mismatch negativity (MMN). Although both groups of L2 learners showed similar behavioral identification features for the Mandarin tonal continuum as native speakers, L2 learners with nontonal L1, as compared with both native speakers and L2 learners with tonal L1, showed longer reaction time to the tokens of the Mandarin tonal continuum. More importantly, the MMN data further revealed distinct roles of acoustic and phonological information on the automatic processing of L2 lexical tones between the two groups of L2 learners. Taken together, the results indicate that the processing of acoustic and phonological information in L2 lexical tones may be modulated by L1 experience with a tonal language. The theoretical implications of the current study are discussed in light of models of L2 speech learning.