Field Size Evaluation with a High Resolution 2D Diode Array for Variable-Aperture Collimators Used in Robotic Radiosurgery

Robotic radiosurgery/Radiotherapy is increasingly adopted in clinics, and quality assurance (QA) of CyberKnife’s variable-aperture IrisTM collimators requires sub-millimeter precision. Conventional film-based QA for the 12 IrisTM cone sizes (ranging from 5 to 60 mm) is both time consuming (120 minutes for all or 30 minutes for 3 cone sizes) and highly experience dependent. To improve the efficiency, a high-resolution 2D diode detector array, sampling every 2.5 mm, was evaluated for IrisTM aperture size QA. This study focused on a spatial frequency analysis, a dose profile reconstruction, and a sensitivity study to beam size variances. Dose profiles of the 12 cones scanned with a high-resolution diode in a water tank were utilized as the gold standard for comparison. Spatial Fourier transform of these profiles were analyzed to explore applicable sampling frequency. Next, the dose profiles were artificially sampled with a 2.5 mm gap, and then interpolated using a Python-based cubic B-spline. Finally, sensitivity of the diode array system to various field sizes was measured by changing source to detector distance. We found, utilizing the diodes system, QA time was reduced to less than 10 minutes. Spatial frequency of the dose profile showed little contribution beyond 0.2 mm-1, so a Nyquist sampling of 0.4 mm-1 is appropriate for dose verification, corresponding to a 2.5 mm gap. Dose profiles were reconstructed using Cubic B-spline with good agreements to nominal for cones 7.5 mm and larger. The measured IrisTM size using the SRS MapCheck had a standard error of ±0.12 mm. Primarily, the 2D Diode array with a spatial resolution 0.4 mm-1 is appropriate for dose verification for these cones above 7.5 mm, and its application would substantially improve IrisTM QA efficiency.

Numerical Study on Mechanism of Blast-Induced Damage Considering Guiding Effect of Water Jet Slot

Damage is one of the most important characteristics of rock failure.Studying the damage mechanism of rock blasting under the guiding effect of the water jet slot and revealing the mechanism of controlled blasting with water jet assistance are crucial.In this study,a rock-like material was chosen as the research object for the calibration experiment of the numerical model.The numerical simulation models were then established by ANSYS/LS-DYNA,and the blastinduced damage mechanism under the guiding effect of the water jet slot was analyzed according to the blasting theory.The results indicated that explosive energy accumulates toward the direction of the slot as the guiding effect of the water jet slot,which allows the rock mass in the direction of the slot bear more damage.Meanwhile,the rock mass in the middle of the connection line between two blast-holes bears more damage under the combination of the effect of the explosion stress wave and guiding effect of water the jet slot on the detonation gas during double-slotted borehole blasting,which results in the formation of a gourd-shaped blast-induced damage area.In addition,the influence of the water jet slot on blast-induced damage varies depending on the blasting-process stage.

原位法制备聚乙二醇/聚(丙烯酰胺-co-丙烯酸)荧光水凝胶

在丙烯酰胺和丙烯酸共聚交联网络中掺入线型聚乙二醇(PEG)形成半互穿聚合物网络结构以提高水凝胶的力学性能,同时引入柠檬酸(CA)和乙二胺(EDA)原位反应形成非共轭型荧光聚合物点(NCPD),一步制备了具有高回弹性的聚乙二醇/聚(丙烯酰胺-co-丙烯酸)PEG/P(AM-co-AA)荧光水凝胶。该水凝胶具有良好的力学强度、韧性,高荧光强度和荧光均一性,且光致发光具有金属离子敏感性。拉伸测试结果表明,PEG/P(AM-co-AA)荧光水凝胶的断裂强度达到~192.2 kPa,拉伸4倍后仍可以恢复到初始状态。光致发光研究结果表明,水凝胶在365 nm的波长激发下,可以发出明亮的蓝色荧光(发射波长434~467 nm)。荧光性能具有强Fe敏感性,猝灭效率可达99%。该荧光水凝胶在柔性电子器件和生物传感等领域具有潜在应用。

Target migration from re-inflation of adjacent atelectasis during lung stereotactic body radiotherapy

Stereotactic body radiotherapy(SBRT) is a widely accepted option for the treatment of medically inoperable early-stage non-small cell lung cancer(NSCLC).Herein,we highlight the importance of interfraction image guidance during SBRT.We describe a case of earlystage NSCLC associated with segmental atelectasis that translocated 15 mm anteroinferiorly due to re-expansion of the adjacent segmental atelectasis following the first fraction.The case exemplifies the importance of crosssectional image-guided radiotherapy that shows the intended target,as opposed to aligning based on rigid anatomy alone,especially in cases associated with potentially "volatile" anatomic areas.

晶面空间分离型聚三嗪亚胺基氮化碳纳米球用于光催化全分解水研究

通过传统熔盐法合成的聚三嗪亚胺(PTI)其六棱柱晶体倾向于沿熔盐模板生长为聚晶形态,这使得其侧面活性面难以充分暴露.在本文中,我们通过耦合熔盐法和硬模板法制备得到了具有高结晶性和侧面暴露的PTI纳米球.研究表明,熔点合适的LiCl/NaCl二元熔盐促进了高结晶六棱柱的形成,此外,三维模板使六棱柱能够沿空间分离方向定向生长.优化后的PTI显示出具有完全扩展的π共轭聚合结构,且具有空间暴露更完全的活性晶面.因此,制备得到的PTI纳米球光催化全分解水性能得到显著提升.

Salt-melt synthesis of poly(heptazine imide)in binary alkali metal bromides for enhanced visible-light photocatalytic hydrogen production

Poly(heptazine imide)(PHI),a semicrystalline version of carbon nitride photocatalyst based on heptazine units,has gained significant attention for solar H_(2)production benefiting from its advantages including molecular synthetic versatility,excellent physicochemical stability and suitable energy band structure to capture visible photons.Typically,PHI is obtained in saltmelt synthesis in the presence of alkali metal chlorides.Herein,we examined the role of binary alkali metal bromides(LiBr/NaBr)with diverse compositions and melting points to rationally modulate the polymerization process,structure,and properties of PHI.Solid characterizations revealed that semicrystalline PHI with a condensedπ-conjugated system and rapid charge separation rates were obtained in the presence of LiBr/NaBr.Accordingly,the apparent quantum yield of hydrogen using the optimized PHI reaches up to 62.3%at 420 nm.The density functional theory calculation shows that the dehydrogenation of the ethylene glycol has a lower energy barrier than the dehydrogenation of the other alcohols from the thermodynamic point of view.This study holds great promise for rational modulation of the structure and properties of conjugated polymeric materials.

Extended light absorption and accelerated charge migration in ultrathin twisted carbon nitride nanoplates for efficient solar hydrogen production

Polymeric carbon nitride has been widely developed as a promising photocatalyst for solar hydrogen production via photocatalytic water splitting.However,pristine carbon nitride prepared by traditional solid-state polymerization usually encounters issues such as rapid carrier recombination and insufficient absorption of visible light below 460 nm.Herein,poly(heptazine imide)with a distinctive nanoplate structure was synthesized in a binary molten salt of NaCl–CaCl_(2).The salt template allows the formation of the thin nanoplate structure,which promotes the charge separation and migration.Besides,the intercalation of Ca^(2+)ions between the conjugated layers endows the activation of n–π*electron transition due to the distortion of in-plane heptazine layers.Accordingly,the optimized poly(heptazine imide)nanoplates achieve an apparent quantum efficiency of up to 17.3%at 500 nm for photocatalytic hydrogen production from water.This work shares new idea for rational control of the optical absorption and charge carrier dynamics of poly(heptazine imide).

Defect and nanostructure engineering of polymeric carbon nitride for visible-light-driven CO_(2) reduction

Sunlight-induced photocatalytic carbon dioxide(CO_(2))reduction to energy-rich chemicals by metal-free polymeric carbon nitride(CN)semiconductor is a promising tactic for sustained solar fuel production.However,the reaction efficiency of CO_(2)photoreduction is restrained seriously by the rapid recombination of photogenerated carriers on CN polymer.Herein,we incorporate 2-aminopyridine molecule with strong electron-withdrawing group into the skeleton edge of CN layers through a facile one-pot thermal polymerization strategy using urea as the precursor,which renders a modified carbon nitride(ACN)with extended optical harvesting,abundant nitrogen defects and ultrathin nanosheet structure.Consequently,the ACN photocatalyst with desirable structural features attains enhanced separation and migration of photoexcited charge carriers.Under visible light irradiation with Co(bpy)^(2+)_(3)as a cocatalyst,the optimized ACN sample manifests a high CO_(2)deoxygnative reduction activity and high sta-bility,providing a CO yielding rate of 17μmol h^(-1),which is significantly higher than that of pristine CN.The key intermediates engaged in CO_(2)photoreduction reaction are determined by the in situ diffuse reflectance infrared Fourier transform spectroscopy,which sponsors the construction of the possible photocatalytic CO_(2)reduction mechanism on ACN nanosheets.

Click chemistry extracellular vesicle/peptide/chemokine nanocarriers for treating central nervous system injuries

Central nervous system(CNS)injuries,including stroke,traumatic brain injury,and spinal cord injury,are essential causes of death and long-term disability and are difficult to cure,mainly due to the limited neuron regeneration and the glial scar formation.Herein,we apply extracellular vesicles(EVs)secreted by M2 microglia to improve the differentiation of neural stem cells(NSCs)at the injured site,and simultaneously modify them with the injured vascular targeting peptide(DA7R)and the stem cell recruiting factor(SDF-1)on their surface via copper-free click chemistry to recruit NSCs,inducing their neuronal differentiation,and serving as the nanocarriers at the injured site(Dual-EV).Results prove that the Dual-EV could target human umbilical vascular endothelial cells(HUVECs),recruit NSCs,and promote the neuronal differentiation of NSCs in vitro.Furthermore,10 miRNAs are found to be upregulated in Dual-M2-EVs compared to Dual-M0-EVs via bioinformatic analysis,and further NSC differentiation experiment by flow cytometry reveals that among these miRNAs,miR30b-3p,miR-222-3p,miR-129-5p,and miR-155-5p may exert effect of inducing NSC to differentiate into neurons.In vivo experiments show that Dual-EV nanocarriers achieve improved accumulation in the ischemic area of stroke model mice,potentiate NSCs recruitment,and increase neurogenesis.This work provides new insights for the treatment of neuronal regeneration after CNS injuries as well as endogenous stem cells,and the click chemistry EV/peptide/chemokine and related nanocarriers for improving human health.

Advances in extracellular vesicle functionalization strategies for tissue regeneration

Extracellular vesicles(EVs)are nano-scale vesicles derived by cell secretion with unique advantages such as promoting cell proliferation,anti-inflammation,promoting blood vessels and regulating cell differentiation,which benefit their wide applications in regenerative medicine.However,the in vivo therapeutic effect of EVs still greatly restricted by several obstacles,including the off-targetability,rapid blood clearance,and undesired release.To address these issues,biomedical engineering techniques are vastly explored.This review summarizes different strategies to enhance EV functions from the perspective of drug loading,modification,and combination of biomaterials,and emphatically introduces the latest developments of functionalized EV-loaded biomaterials in different diseases,including cardio-vascular system diseases,osteochondral disorders,wound healing,nerve injuries.Challenges and future directions of EVs are also discussed.

Downstream Channel Evolution and Its Causes in the Yuan River during the Qing Dynasty

The determination of channel evolutions and the causes is important for reconstructing the evolutionary history of river landforms.This study aimed to elucidate the downstream channel evolution of the Yuan River in Hunan Province,China,during the Qing Dynasty via Landsat 8 satellite image data and relevant literature.The objective was to establish the modes of channel evolution and discuss the significance of historical climate change.The downstream paleochannel of the Yuan River was identified in the Late Ming Dynasty and Early Qing Dynasty(1600–1644 AD),the Kangxi-Qianlong periods of the Qing Dynasty(1661–1796 AD),the Late Qing Dynasty(1840–1912 AD),and the World War II(1939–1945 AD),and three main modes of river evolution were determined.Using remote sensing data and the ancient literature,the evolution characteristics of the paleochannel in the Lower Yuan River were analyzed and its distribution across historical periods was comprehensively revealed.The findings reveal a strong correlation between channel evolution,flood events,and climate change.Numerous flood events that occurred from the Late Qing Dynasty to the World War II caused a high rate of channel evolution,demonstrating the combined effects of climate change and human activities.These findings will help adopt robust and resilient hydrological management methods in the future of a changing climate.

Engineered extracellular vesicles for ischemic stroke treatment

Dear Editor,Nanotechnology-based therapeutic strategies have been proven effective in diseases including cancer,infection,inflammation,etc.1 However,the application of nanotechnology is greatly restricted in the treatment of central nervous system(CNS)disorders due to physiological CNS barriers.For example,the blood-brain barrier(BBB)can be the“Maginot line”for pharmacologically active molecules,blocking them out of the CNS.

Characterization of viromes within mosquito species in China

Mosquitoes are vectors of multiple disease-causing agents that cause worldwide outbreaks of serious infectious diseases in both humans and animals. These arboviral agents include Dengue virus (DENV), Zika virus (ZIKV), chikungunya virus, yellow fever virus, Japanese encephalitis virus (JEV),and Rift Valley fever virus. Thus, mosquitoes are key to the study of viral origin, spread, and the epidemic tendency of these infectious diseases (Hall and Macdonald, 2016).

Ultrafast Photoinduced Electron Transfer in a Photosensitizer Protein

Photosystem Ⅱ(PSⅡ)is a large membrane protein(∼700 kDa)complex,harboring P680+,the strongest oxidant known in biological systems,which is responsible for driving tyrosine oxidation and ultimately O_(2) generation.While the enhancement and expansion of PSⅡ functions through genetic engineering would be beneficial for driving challenging chemical reactions,this has proven difficult due to its enormous complexity.Here,we report a genetically encoded,27 kDa photosensitizer protein(PSP3)that recapitulates the initial photoinduced key properties of PSⅡ.Through the genetic incorporation of benzophenone-alanine(BpA)into a fluorescent protein coupled with femtosecond transient absorption measurement,we show that photoinduced electron transfer from residue Tyr203 to the PSP3 chromophore occurs very rapidly(∼1 ps),which is comparable with that of the first electron transfer step in PSII.Since PSP3 can be overexpressed in high yield in Escherichia coli and genetically engineered easily,it might facilitate challenging oxidation and reduction reactions in vitro and in vivo.