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Seed dormancy-break via cold stratification is of fundamental importance for plant adaptation to environmental conditions and response to climate change through timing germination, seedling emergence and consequently community dynamics. Although cold stratification requirements for dormancy break vary among species, it is not known if this variation is determined by the environmental conditions experienced by seeds or by differences among species. We determined the soil moisture content and duration of cold stratification required for seed dormancy-break of species from alpine and desert habitats (soil moisture content: 20 and 18 species from alpine and desert habitats, respectively; duration: 16 and 16 species from the alpine and desert, respectively), and examined the correlation between environmental conditions (soil moisture content and duration of cold stratification) required for dormancy-break and seed traits. Seed germination increased and then decreased as soil moisture content or duration of cold stratification increased. The optimal and critical soil moisture content for seed dormancy-break were higher for alpine species than desert species. A positive correlation between optimal soil moisture content and seed shape was found. However, the duration of cold stratification required for dormancy-break was not related to habitat, seed mass or seed shape. Our results suggest that soil moisture content rather than duration of cold stratification resulting from climate change could affect seed germination and consequently seedling emergence and establishment, especially for desert species.

An integrated understanding of the ecophysiological mechanisms of persistence of buried seeds is essential for understanding plant community dynamics and improving our ability to accurately predict seed persistence. However, little is known about how the interaction of precipitation and microorganisms affects persistence of buried seeds and how well seed traits predict seed persistence, especially in a changing environment. Here we determined the combined effect of precipitation and microorganisms on the persistence of buried seeds of 11 species from the Loess Plateau in China, and examined the correlation between seed persistence and seed traits, including seed mass, seed dimensions, seed shape, seed toughness, seed water absorption, total phenolic content, crude protein content and seed longevity. Seed persistence of all species decreased with increasing precipitation. Fungicide treatment improved seed persistence of all tested species, while the effect size of fungicide treatment on persistence increased with increasing of precipitation. Persistence was positively correlated with seed longevity (P50), seed toughness and total phenolic content in all treatments. Seed water absorption was not correlated with seed persistence. However, the relationship between seed persistence and seed shape, seed mass, crude protein content, seed germination was strongly dependent on environmental conditions. Changes in precipitation not only affected seed persistence but also the relationship between seed persistence and seed traits. Thus, environmental factors should be fully considered in making predictions about seed persistence based on seed traits.

INTRODUCTION: Transferring genes safely, targeting cells and achieving efficient transfection are urgent problems in gene therapy that need to be solved. Combining microbubbles (MBs) and viruses to construct double vectors has become a promising approach for gene delivery. Understanding the characteristic performance of MBs that carry genes is key to promoting effective gene transfer. Therefore, in this study, we constructed MB-adenovirus vectors and discussed their general characteristics. METHODS: We constructed MB-adenovirus vectors carrying the chemokine (C-X-C motif) ligand 12 (Cxcl12) and bone morphogenetic protein-2 (Bmp2) genes (pAd-Cxcl12 and pAd-Bmp2, respectively) to explore the general characteristics of double vectors carrying genes. RESULTS: The MB-adenovirus vectors had stable physical properties, and no significant differences in diameter, concentration, or pH were noted compared with naked MBs (p > 0.05). Flow cytometry and RT-PCR were used to detect the gene-loading capacity of MBs. The gene-loading efficiency of MBs increased with increasing virus amounts and was highest (91%) when 10.0 µL of virus was added. Beyond 10.0 µL of added virus, the gene-loading efficiency of MBs decreased with the continuous addition of virus. The maximum amounts of pAd-Cxcl12 and pAd-Bmp2 in 100 µL of MBs were approximately 14 and 10 µL, respectively. CONCLUSIONS: This study indicates that addition of an inappropriate viral load will result in low MB loading efficiency, and the maximum amount of genes loaded by MBs may differ based on the genes carried by the virus.

It is hard to remove sweet clover seeds from alfalfa seed lots by conventional methods, affecting the purity of seed lots and resulting losses in for alfalfa hay production as well as seed yield. However, the discrimination of sweet clover seed contaminates in alfalfa seed lots is difficult without special training. In this study, multispectral imaging with object-wise multivariate image analysis was evaluated for its potential to separate sweet clover and alfalfa seeds. Principal component analysis (PCA), linear discrimination analysis (LDA), partial least squares discriminant analysis (PLSDA), AdaBoost and support vector machine (SVM) methods were applied to classify seeds of sweet clover and alfalfa according to their morphological features and spectral traits or a combination thereof. The results showed that an excellent classification could be achieved based on a combination of morphological features and spectral data in a tested data set. Seed classification accuracy was up to 99.58% in a validation set with the LDA model, which was better than the PLSDA (68.19%), AdaBoost (96.95%) and SVM (98.47%) models. Thus, multispectral imaging together with chemometric multivariate analysis is a promising technique to identify sweet clover seeds in alfalfa seed lots with high efficiency.

Background: Hepatocellular carcinoma (HCC) is the most common primary malignant tumor in the liver. Partial hepatectomy is one of the most effective therapies for HCC but suffer from the high recurrence rate. At present, the studies of association between clinical outcomes and CT features of patients with HCCs undergoing partial hepatectomy are still limited. The purpose of this study is to determine the predictive CT features and establish a model for predicting relapse or metastasis in patients with primary hepatocellular carcinomas (HCCs) undergoing partial hepatectomy.Methods: The clinical data and CT features of 112 patients with histopathologically confirmed primary HCCs were retrospectively reviewed. The clinical outcomes were categorized into two groups according to whether relapse or metastasis occurred within 2 years after partial hepatectomy. The association between clinical outcomes and CT features including tumour size, margin, shape, vascular invasion (VI), arterial phase hyperenhancement, washout appearance, capsule appearance, satellite lesion, involvement segment, cirrhosis, peritumoral enhancement and necrosis was analyzed using univariate analysis and binary logistic regression. Then establish logistic regression model, followed by receiver operating characteristic (ROC) curve analysis.Results: CT features including tumor size, margin, shape, VI, washout appearance, satellite lesion, involvement segment, peritumoral enhancement and necrosis were associated with clinical outcomes, as determined by univariate analysis (POR=6.41 and 10.92 respectively). The logistic regression model was logit(p)=-1.55+1.86 margin +2.39 VI. ROC curve analysis showed that the area under curve of the obtained logistic regression model was 0.887(95% CI：0.827-0.947).Conclusion: Patients with ill-defined margin or VI of HCCs were independent risk predictors of poor clinical outcome after partial hepatectomy. The model as logit(p)= -1.55+1.86 margin +2.39 VI was a good predictor of the clinical outcomes.

Chen Yuan,1,* Yanhong Li,1,* Liyun Liu,1 Baihetiya Tayier,1 Lingjie Yang,1 Lina Guan,1– 3 Yuming Mu1– 3 1Department of Echocardiography, First Affiliated Hospital of Xinjiang Medical University, Urumqi, 830011, People’s Republic of China; 2State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, First Affiliated Hospital of Xinjiang Medical University, Urumqi, People’s Republic of China; 3Xinjiang Key Laboratory of Medical Animal Model Research, Clinical Medical Research Institute of First Affiliated Hospital of Xinjiang Medical University, Urumqi, People’s Republic of China*These authors contributed equally to this workCorrespondence: Yuming Mu; Lina GuanDepartment of Echocardiography, The First Affiliated Hospital of Xinjiang Medical University, 137 Liyushan Road, Ürümqi, Xinjiang Uyghur, Autonomous Region, 830054, People’s Republic of ChinaEmail mym1234@126.com; sanjin_lsx@163.comObjective: To prepare a new type of dual-target microbubble loaded with anti-miR-33 (ANM33).Methods: Carrier core nanobubbles (NBs) were prepared by thin film hydration, and microbubbles loaded with PM1 (PCNBs) were prepared by grafting DSPE-PEG2000-maleimide-PM1 onto the NB surface. ANM33 was connected via electrostatic adsorption and covalent bonding, and hyaluronic acid (HA) was covalently connected. PM1 and HA were the targets, and ANM33 was the intervention drug. To evaluate the general physical and chemical properties of the prepared dual-target microbubbles loaded with ANM33 (HA-PANBs), we observed their morphology, particle size and surface potential while monitoring their stability and in vitro imaging ability, evaluated their toxic effect on cells and verified their ability to target cells.Results: HA-PANBs had a regular morphology and good stability. The average particle size measured by a Malvern potentiometer was 1421.75± 163.23 nm, and the average surface potential was − 5.51± 1.87 mV. PM1 and ANM33 were effectively connected to the NBs. The PM1, ANM33, and HA binding reached 89.0± 1.1%, 65.02± 5.0%, and 61.4± 3.5%, respectively, and the maximum binding reached 2 μg, 5 μg, and 7 μg/108 microbubbles, respectively. HA-PANBs had no obvious toxic effects on cells, and their ability to continuously enhance imaging in vitro persisted for more than 15 minutes, obviously targeting foam cells in the early stage of AS.Conclusion: HA-PANBs are ideal ultrasound contrast agents. The successful, firm connection of PM1 and HA to the NBs significantly increased the amount of carried ANM33. When microbubbles prepared with 2:4:7 PM1:ANM33:HA were used as a contrast agent, they had a high ANM33 carrying capacity, stable physical properties, and significantly enhanced imaging and targeting of foam cells in the early stage of AS.Keywords: ultrasound microbubbles, molecular targeting, dual targeting, atherosclerosis

Acute myocardial infarction (AMI) is a serious threat to human health. Stem cells can serve as ideal seed cells for myocardial repair and regeneration; however, insufficient homing to the infarcted areas and poor myocardial differentiation limit their further clinical application. Chemokine (C-X-C motif) ligand 12 (CXCL12) is an important stem cell homing factor, and Bone morphogenetic protein-2 (BMP2) is a differentiation-promoting factor. In this study, we designed microbubbleadenovirus complexes and investigated the functional benefit of co-delivery of Cxcl12 and Bmp2 genes in adenoviral vectors by ultrasound-targeted microbubble destruction (UTMD) for myocardial repair in AMI rats. By transfection of rat bone marrow mesenchymal stem cells (BMSCs), high transfection efficiency was achieved under ultrasound irradiation, and successful myocardial differentiation of the transfected BMSCs was induced after ultrasound-mediated-transfection of Bmp2 in vitro. In the AMI rat model, co-delivery of Cxcl12 and Bmp2 at a ratio of 2:1 may result in significantly higher myocardial repair efficacy compared to transfection of Cxcl12 or Bmp2 only. Higher myocardial repairing efficacy was achieved with co-delivery of Cxcl12 and Bmp2 at a ratio of 2:1 than using a ratio of 1:1 or 1:2, as evidenced by smaller infarction size, higher micro-vessel density, and better recovery of cardiac function at 28 days after treatment. Hence, UTMD-mediated co-transfection of Cxcl12 and Bmp2 significantly promoted the repair/regeneration of the infarcted myocardium, thereby providing a promising approach for the repair of cardiac injury.

Pulmonary microvascular endothelial cell (PMVEC) apoptosis is the initial stage of adult pulmonary hypertension (PH), which involves high pulmonary arterial pressure and pulmonary vascular remodeling. However, the mechanism regulating PMVEC apoptosis and its involvement in the early stages of neonatal hypoxic PH (HPH) pathogenesis are currently unclear. The present study aimed to investigate the effects of heat shock protein 70 (HSP70) on hypoxia-induced apoptosis in PMVECs. PMVECs isolated from neonatal Sprague-Dawley rats were transfected with lentivirus with or without HSP70, or treated with the synthetic HSP70 inhibitor N-formyl-3,4-methylenedioxy-benzylidene-g-butyrolactam under hypoxic conditions (5% O2) for 24, 48 or 72 h. PMVEC apoptosis was evaluated by performing flow cytometry and mitochondrial membrane potential (MMP) assays. The expression levels of HSP70, hypoxia-inducible factor-1α (HIF-1α) and apoptosis-associated proteins were determined by conducting reverse transcription-quantitative PCR and western blotting. Following 24, 48 or 72 h of hypoxia, the apoptotic rates of PMVECs were significantly elevated compared with cells under normoxic conditions. The MMP was significantly reduced, whereas the mRNA and protein expression levels of HIF-1α, cytochrome c (cyt C), caspase-3 and HSP70 were enhanced by hypoxia compared with those under normoxic conditions. Additionally, the mRNA and protein expression levels of B-cell lymphoma 2 (Bcl-2) were significantly downregulated in the hypoxia group compared with those in the normoxia group. In hypoxic PMVECs, HSP70 overexpression decreased the apoptotic rate and the expression levels of cyt C, downregulated the expression levels of caspase-3 and HIF-1α, and increased the MMP and the expression levels of Bcl-2. HSP70 inhibition resulted in the opposite outcomes compared with those of HSP70 overexpression. Therefore, the results of the present study suggested that HSP70 may inhibit mitochondrial pathway-mediated apoptosis in isolated neonatal rat PMVECs in early-stage hypoxia, which may be associated with HSP70-mediated HIF-1α downregulation. Overall, HSP70 may be protective against neonatal HPH through the HSP70/HIF-1α pathway.

In recent years, the demand for improving the autonomy of UAVs has continued to increase in the civilian and military fields. Collision detection and avoidance is one of the key technologies to this end. In this paper, we propose a fully-distributed collision detection and avoidance method for multi-UAV based on deep reinforcement learning. Different from traditional methods, we implement an end-to-end control, which takes the information of sensor, UAV status and destination as inputs, and directly outputs the control references. Besides, based on the PPO algorithm and the paradigm of centralized training and decentralized execution, we provide the design of the deep reinforcement leaning network and the policy update strategy. In addition, we build a series of training and verification environments, including 2D Stage scenes and 3D Gazebo scenes. The experiment results show that our method can successfully avoid the obstacles and achieve no collision between UAVs.

Myocardial contrast echocardiography (MCE) and two-dimensional speckle tracking echocardiography (2D-STE) were used to detect left ventricular myocardial microcirculation perfusion and myocardial systolic function in dilated cardiomyopathy (DCM) and to explore the relationship between the two.Conventional ultrasound, MCE, and 2D-STE examinations were performed on 30 patients and 30 controls. Left ventricular microcirculation perfusion, left ventricular longitudinal strain (GLS), and circumferential strain (GCS) were analyzed to further compare the correlation between left ventricular perfusion and myocardial strain parameters.Regional myocardial perfusion was reduced in patients with DCM, manifesting as a decrease in the rising slope (A) of the mid-segment of the posterior septum, the peak intensity (PI) of the mid-segment of the anterior septum and the posterior septum, the apical segment of the lateral wall, the area under the curve (AUC) of the posterior septum, the basal segment of the posterior wall, the anterior septum, posterior septum, posterior wall, mid-segment of the lateral wall, and apical segment of the lateral wall and the overall average PI and AUC of the mid-segment, compared with that in the controls (P < 0.05). The left ventricular systolic function and the strain parameters GLS and GCS of DCM patients were lower than those of the controls (P < 0.001). Correlation analysis revealed a positive correlation between the A of the mitral valve and GCS (r = 0.372, P = 0.043), and MV-E/e' had a positive correlation with the AUC of the basal and intermediate segments (r = 0.379, P = 0.039; r = 0.404, P = 0.027).In patients with DCM, regional myocardial microcirculation perfusion is reduced, and myocardial strain is impaired. Myocardial perfusion has a good positive correlation with myocardial mechanics.

This paper proposes a control framework to achieve the tracking of the moving target by a fixed-wing unmanned aerial vehicle (UAV) with a monocular pan-tilt camera. This control framework is based on the image-based visual servoing (IBVS) method, which takes the target feature point on the captured image as the input and outputs the control signals directly with the aid of image Jacobian matrix. However, the image is affected by the attitude of both the UAV and the pan-tilt, and the attitude of the pan-tilt is coupled with that of the UAV simultaneously. To solve this problem, we present an "Ideal State" as the reference state, and make sure the coordinates of the feature point in the state are only affected by the change of the yaw angle of the UAV. In this way, we can integrate the attitude control of the UAV and the pan-tilt. By using this control framework, the fixed-wing UAV can track the ground target continuously on the one hand, and the target will tend to locate at image center on the other hand. This prevents the target from moving toward to the edge of the image or even disappearing. Besides, we prove the controller is exponentially convergent by the Lyapunov method. In order to evaluate the performance of our controller, we build a hardware-in-the-loop (HIL) simulation platform and a prototype platform. Based on these platforms, extensive experiments including simulations and real flight tests are conducted. The results show that our controller can achieve continuous and robust tracking of the target with a speed of 20km/h when the speed of the UAV is 16m/s.

Background Physical dormancy (hard seed) occurs in most species of Leguminosae family and has great consequences not only for ecological adaptation but also for agricultural practice of these species. A rapid, nondestructive and on-site screening method to detect hard seed within species is fundamental important for maintaining seed vigor and germplasm storage as well as understanding seed adaptation to various environment. In this study, the potential of multispectral imaging with object-wise multivariate image analysis was evaluated as a way to identify hard and soft seeds in Acacia seyal, Galega orientulis, Glycyrrhiza glabra, Medicago sativa, Melilotus officinalis, and Thermopsis lanceolata. Principal component analysis (PCA), linear discrimination analysis (LDA), and support vector machines (SVM) methods were applied to classify hard and soft seeds according to their morphological features and spectral traits. Results The performance of discrimination model via multispectral imaging analysis was varied with species. For M. officinalis, M. sativa, and G. orientulis, an excellent classification could be achieved in an independent validation data set. LDA model had the best calibration and validation abilities with the accuracy up to 90% for M. sativa. SVM got excellent seed discrimination results with classification accuracy of 91.67% and 87.5% for M. officinalis and G. orientulis, respectively. However, both LDA and SVM model failed to discriminate hard and soft seeds in A. seyal, G. glabra, and T. lanceolate. Conclusions Multispectral imaging together with multivariate analysis could be a promising technique to identify single hard seed in some legume species with high efficiency. More legume species with physical dormancy need to be studied in future research to extend the use of multispectral imaging techniques.

This paper presents an optimized image-based visual servo (IBVS) control scheme for tracking a ground target by using a fixed-wing unmanned aerial vehicle (UAV) with a monocular camera fixed on it. Unlike the widely used rotor UAVs, the fixed-wing UAV has much more dynamical constraints such as it cannot move omni-direction and its minimum speed is limited by the stalling speed. This makes the target tracking problem more challenging. The proposed scheme leverages the image Jacobian matrix to build a connection between the velocity of the feature point and that of the UAV. Afterward, considering the camera is fixed on the body of the UAV, an “ideal camera” model is proposed to compensate the shifts of the feature point caused by the changes of the UAV's attitude. Then, an optimized control law without solving the pseudo-inverse of the image Jacobian matrix is proposed with the aid of the least square method from the target center in the image coordinate system. This control law takes the velocity of the feature point as inputs and the yaw angular velocity of the UAV as outputs. The stability of the proposed law is analyzed with the Lyapunov method, showing that the UAV will circle around the ground target asymptotically. Finally, the proposed scheme is evaluated by a hardware-in-the-loop (HIL) simulation based on the Gazebo simulator and the off-the-shelf autopilot hardware.

Additional file 1: Figure S1. First two principal components score for hard and soft seeds.

Additional file 3: Figure S3. First ten principal components score for hard and soft seeds.

Additional file 4: Table S1. List of the 15 extracted variables from multi spectral images.

Additional file 2: Figure S2. First three principal components score for hard and soft seeds.

This paper presents a new image-based visual servo (IBVS) control algorithm for the tracking of a static target by a fixed-wing unmanned aerial vehicle (UAV). The sensor used is a monocular camera fixed on the drone. The centroid coordinates of the target are extracted to be the inputs of the algorithm, while the control output is obtained to adjust the heading direction of the drone by the image Jacobian model. Besides, the problem that the shifts of the centroid caused by the changes of the UAV’s attitude during tracking can be solved by a compensation mechanism. Through experiments by the hardware-in-the-loop (HIL) simulation, we evaluate the proposed algorithm. The results show that the proposed algorithm can effectively track the static target by a fixed-wing UAV.

Acute myocardial infarction (AMI) is a serious threat to human health. Stem cells can serve as ideal seed cells for myocardial repair and regeneration; however, insufficient homing to the infarcted areas and poor myocardial differentiation limit their further clinical application. Chemokine (C-X-C motif) ligand 12 (CXCL12) is an important stem cell homing factor, and Bone morphogenetic protein-2 (BMP2) is a differentiation-promoting factor. In this study, we designed microbubbleadenovirus complexes and investigated the functional benefit of co-delivery of

Microcirculation disturbance is a crucial pathological basis of heart damage; however, microcirculation alterations induced by hypoxic pulmonary hypertension (HPH) remain unknown, and the left ventricle (LV) in HPH is conventionally ignored. Herein, we investigated the changes in the cardiac structure, function and microcirculation after HPH and further compared the differences between the right ventricle (RV) and LV. Using a neonatal rat model of HPH, we found RV myocardial hypertrophy, dysfunction and poor myocardial perfusion in HPH rats. Additionally, RV microcirculation disturbance manifested as the abnormal expression of endothelin-1/eNOS and increased expression of intercellular cell adhesion molecule-1 (ICAM-1) or E-selectin 3 days after hypoxia, followed by vascular inflammation, coronary arterial remodeling and microvascular sparseness. Impairment in LV vasodilation was detected in rats after 3 days of hypoxia; however, no obvious microvascular rarefaction or inflammatory reaction was observed in the LV. In conclusion, our results suggest that HPH mainly triggers RV microcirculation disturbances, causing low myocardial perfusion damage and cardiac dysfunction. Despite the differences in the RV and LV, their impaired microvascular function, mediated by endothelial cells, occurs almost simultaneously after HPH, earlier than cardiac functional or structural abnormalities.

Stem cells can promote myocardial regeneration and accelerate the formation of new blood vessels. As such, transplanted stem cells represent a promising treatment modality for acute myocardial infarction (AMI). Stem cells spontaneously home to the infarcted myocardium using chemotaxis, in which the stromal cell-derived factor (SDF-1α) has been shown to be one of the most important chemokines. However, spontaneously secreted SDF-1α is short-lived, and therefore does not meet the needs of tissue repair. In this study, adenoviruses carrying SDF-1α genes were loaded on microbubble carriers and the adenoviruses were released into AMI rats by ultrasound targeted microbubble destruction. The possibility of in vivo self-transplantation of bone marrow mesenchymal stem cells (BMSCs) induced by overexpression of SDF-1α in the infarcted myocardium was explored by detecting the number of BMSCs homing from the peripheral blood to the myocardial infarcts. The concentration of SDF-1α in peripheral blood was significantly higher after transfection, and the number of BMSCs was significantly higher in the peripheral blood and infarcted area. Further analyses indicated that the number of homing BMSCs increased with increased SDF-1α expression. In conclusion, our results suggest that ultrasound mediated transduction of exogenous SDF-1α genes into myocardial infarcted AMI rats can effectively promote the homing of endogenous BMSCs into the heart. Moreover, the number of homing stem cells was controlled by the level of SDF-1α expression.

To evaluate the changes in left atrial (LA) volume and function in patients with severe multi-vessel coronary artery disease (CAD) by real-time three-dimensional echocardiography (RT-3DE). One hundred and eight subjects were stratified based on coronary angiography (CAG) imaging, comprising 48 patients with severe multi-vessel CAD, 31 patients with severe single-vessel CAD, and 29 controls. RT-3DE was performed in all groups. LA volume parameters were measured. LA ejection fractions (EF) and LA function index (LAFI) were also calculated. There were no significant differences between the single-vessel CAD group and the control group, while LA passive emptying fraction (LAVpEF) was significantly reduced in the single-vessel CAD group. In the multi-vessel CAD group, LAVpEF and LAFI were lower, while LA presystolic volume (LAVpre) was prominently higher as compared with the other groups, and LA active emptying volume (LAVa) was higher than that in the control group (p