犬恒牙牙根发育过程中牙髓炎症对细胞凋亡的影响

目的：探讨牙髓炎症对牙根发育过程中细胞凋亡的影响。方法：建立犬年轻恒牙实验性牙髓炎模型,采用原位末端标记技术（TUNEL）观测牙根发育过程中犬恒牙牙髓炎症对各组织中凋亡细胞分布的影响。结果：与炎症区相邻的牙髓组织中细胞凋亡数量增多,参与牙根发育的各种功能细胞（成牙本质细胞、成牙骨质细胞、上皮根鞘细胞、成骨细胞和牙周膜细胞）也出现非生理性的凋亡。结论：牙根发育过程中牙髓炎症状态下细胞凋亡一方面参与牙髓组织自身防御,另一方面则干扰了牙根的正常发育。     

Heterogeneous iodine-organic chemistry fast-tracks marine new particle formation

The gas-phase formation of new particles less than 1 nm in size and their subsequent growth significantly alters the availability of cloud condensation nuclei (CCN, >30–50 nm), leading to impacts on cloud reflectance and the global radiative budget. However, this growth cannot be accounted for by condensation of typical species driving the initial nucleation. Here, we present evidence that nucleated iodine oxide clusters provide unique sites for the accelerated growth of organic vapors to overcome the coagulation sink. Heterogeneous reactions form low-volatility organic acids and alkylaminium salts in the particle phase, while further oligomerization of small α-dicarbonyls (e.g., glyoxal) drives the particle growth. This identified heterogeneous mechanism explains the occurrence of particle production events at organic vapor concentrations almost an order of magnitude lower than those required for growth via condensation alone. A notable fraction of iodine associated with these growing particles is recycled back into the gas phase, suggesting an effective transport mechanism for iodine to remote regions, acting as a “catalyst” for nucleation and subsequent new particle production in marine air.

Marine aerosol formation contributes significantly to the global radiative budget given the high susceptibility of marine stratiform cloud radiative properties to changes in cloud condensation nuclei (CCN) availability. Atmospheric new-particle-formation is thought to involve nucleation of sulfuric acid with water, ammonia, or amines followed by condensation/growth in the presence of organic vapors (1, 2). Unique in the marine boundary layer (MBL), new particle formation involves sequential addition of HIO₃ or clustering of iodine oxides (I_xO_y) (3, 4). In specific source regions such as coastal zones, seaweed beds, or snowpack/pack-ice, iodine oxide nucleation can be a driving force for nucleation (5–7). Over Arctic waters, nonetheless, one study finds insufficient iodic acid vapors to grow nucleated particles to CCN sizes (8), whereas another study finds that both nucleation and growth are almost exclusively driven by iodic acid (9). Over the open ocean, the supply of iodine oxides has been thought to be limited; however, recent measurements suggest that significant reactive iodine chemistry can occur in these regions (10). Moreover, observational evidence exists for open ocean particle formation and growth, especially when oceanic productivity is high (11, 12). An increase in atmospheric iodine levels in the North Atlantic since the mid-20th century has been shown to be driven by growth of anthropogenic ozone and enhanced subice phytoplankton production (13). While the reported IO concentration (0.4–3.1 ppt) in the remote MBL (10, 14, 15) is likely sufficient for formation of prenucleation clusters (∼1 nm), growth of these initial clusters requires the presence of other condensable vapors (16). Since preexisting aerosol particles act as a strong sink for the nucleated clusters, thus inhibiting atmospheric aerosol and CCN formation (17, 18), this early growth phase is essential for their survival. Whereas sulfuric acid vapor is also involved in nucleation, its level in remote open ocean is generally too low (10⁵ molecules cm⁻³) to support subsequent particle growth, leaving organic vapors as the most plausible alternative for particle growth.In the marine atmosphere, condensing organics must originate from the oxidation of marine volatile organic compounds (VOCs), which predominantly comprise C₁–C₅ VOCs (e.g., isoprene) released from phytoplankton. Principal high volatility oxidation products consist of intermediate oxidized organics (IOOs), such as polyhydric alcohols (e.g., tetrols) or polyfunctional carbonyls (e.g., glyoxal) (19–22). Nonetheless, growth of available prenucleation clusters/nanometer particles requires condensing organic molecules of low effective volatilities (i.e., saturation mass concentration, C* < ∼10⁻³ μg m⁻³); otherwise, preferential condensation of the organic mass to larger-diameter particles would occur (23, 24). Formation of such extremely low-volatility organic compounds (ELVOCs) from gas-phase reaction is well established for monoterpene oxidation products (25, 26).A potential pathway for formation of low-volatility organics could also result from particle-phase chemical reactions induced by iodine oxides in the early stages of marine particle formation. When the underlying chemistry is sufficiently fast, kinetic condensation occurs, resulting in particles with diameters smaller than about 50 nm growing at the same rate (e.g., nm h⁻¹) (24). If, however, particle-phase chemistry is preferentially favored in the smallest particles (i.e., stemming from the higher relative concentration of iodine oxides in freshly formed marine particles), growth of the nucleated particles could proceed more rapidly, as compared to that in which gas-phase chemistry is the source of the low-volatility compounds (23).In this paper, we present experimental results from field measurements as well as laboratory studies of nanometer particle growth and derive a plausible chemical mechanism from the results that can explain the observations of ultrafine particle growth in the marine atmosphere. The results suggest that both iodine and condensed organics contribute to particle growth from a nascent nucleation mode into an ultrafine particle mode. Moreover, laboratory studies of the growth of seed iodine oxide particles (IOP) via heterogeneous reactions with organic vapors suggest a hitherto unrecognized mechanism that fast-tracks the growth of nucleation mode clusters into survivable aerosol particles. In this process, a notable fraction of the iodine associated with these growing particles is recycled back to the gas phase, suggesting a transport mechanism for iodine to remote regions.     

Research on Design and Performance of Self-Compacting Cement Emulsified Bitumen Mixture (CEBM)

To meet the needs of the road industry for maintenance operations, a new cement emulsified bitumen mixture (CEBM) with early-strength, self-compacting, and room-temperature construction characteristics was designed. The strength formation mechanism of CEBM was revealed with a scanning electron microscope (SEM) and the surface free energy (SFE) theory. The mechanical properties and road performance of the CEBM were investigated extensively. The results show that before the demulsification of emulsified bitumen, the SFE of the bitumen–aggregate–water three-phase system was reduced due to the replacement of the bitumen–aggregate interface with water. The adhesion work between the emulsified bitumen and the aggregate is negative, which means the adhesion between the emulsified bitumen and the aggregate will not occur spontaneously due to the existence of water. The liquid emulsified bitumen improves the workability of the mixture and ensures that the mixture can be evenly mixed and self-compacted. After demulsification, the work of adhesion between the residual bitumen and the aggregate is positive, which means residual bitumen and aggregate can bond spontaneously. In addition, the hydration products of cement and aggregate form a skeleton, and the emulsified bitumen film wraps and bonds the cement and aggregate together, creating strength. The emulsified bitumen, cement content, and curing conditions have significant effects on the stability of CEBM. The recommended dosage of emulsified bitumen and cement is 8% and 8–10%, respectively. This material integrates the hardening effect of cement and the viscoelastic performance of bitumen and has good workability, mechanical properties, and road performance. Therefore, the CEBM is technically feasible for application to bitumen pavement.     

Effect of Non-Thermal Plasma Treatment of Contaminated Zirconia Surface on Porphyromonas gingivalis Adhesion and Osteoblast Viability

Plasma treatment on a zirconia surface prevents bacterial contamination and maintains osteoblast activity. To assess the degree of adhesion of Porphyromonas gingivalis on a zirconia surface after non-thermal plasma (NTP) treatment, specimens were treated with plasma for 60, 300, and 600 s, after which P. gingivalis was inoculated onto the surface and incubated for 48 h. To assess osteoblast activity after NTP treatment, osteoblasts (MC3T3-E1) were dispensed onto the specimens contaminated with P. gingivalis immediately after NTP for 60 and 120 s, followed by incubation for 48, 72, and 96 h. P. gingivalis was cultured after 60 s of NTP treatment of zirconia. The NTP and control groups showed no significant difference (p = 0.91), but adhesion was significantly increased following NTP treatment for 300 s or longer (300, 600 s groups) (p < 0.05). After NTP treatment of P. gingivalis-contaminated zirconia, osteoblast activity significantly increased at 72 and 96 h (I60 and I120 s group) in the groups treated with plasma (p < 0.017). Application of NTP to dental zirconia implants for 60 s not only inhibits the proliferation of P. gingivalis, which causes peri-implantitis but also increases osseointegration on zirconia surfaces contaminated with P. gingivalis.     

Crack-Resistant Amino Resin Flame-Retardant Coatings Using Waterborne Polyurethane as a Co-Binder Resin

Surface cracking is a major issue in amino resin-based flame-retardant coatings, which can be reduced by mixing flexible resins into the coatings. In this study, flexible waterborne polyurethane (WPU) was added into a melamine-modified, urea-formaldehyde, resin-based intumescent flame retardant (MUF-IFR) coating. A molecular chain of WPU was inserted into the MUF network and formed a WPU/MUF-semi-IPN structure. The cracking resistance of the coating was gradually enhanced with the increase in WPU content. When the WPU content exceeded 25% of the total resin, there were no cracks in the coatings after crack-resistance tests. The coatings before and after toughening showed good transparency on wood surfaces. The influence of WPU on char formation and flame retardant properties were explored by TGA, SEM, and cone calorimetry. The results showed that the decomposition of WPU occurred before char formation, which decreased the integrity of the coating and damaged the compactness of the char. Therefore, the addition of WPU reduced the expansion height and the barrier capacity of the char as well as the flame retardant properties of the coating. When the amount of WPU was 25% of the total resin, compared to the non-WPU coating, the average heat release rate in 300 s (AveHRR_300s) and the total heat release at 300 s (THR_300s) of the samples were increased by 45.8% and 35.7%, respectively. However, compared to the naked wood, the peak heat release rate (pHRR₁), AveHRR_300s, and THR_300s of the samples with the coating containing 25% WPU were decreased by 64.2%, 39.0%, and 39.7%, respectively. Therefore, the thermal stability of WPU affected char formation. The amount of WPU added should be chosen to be the amount that was added just before the coating cracked.     

中华猕猴桃的防癌作用——(七)阻断慢性萎缩性胃炎病人体内N-亚硝基脯氨酸合成

本文报导了中华猕猴桃汁阻断慢性萎缩性胃炎(CAG)病人体内N-亚硝基脯氨酸(NPRO)合成的作用。在11名CAG病人的自身对照研究中,病人食入300mg NaNO_3和500mg脯氨酸后,尿中NPRO从本底值26.3nmol升至63.9nmol;同时服4.1ml浓缩猕猴桃汁后,多数人尿中NPRO明显下降,阻断率达94.4％。此外,有2人体内NPRO合成水平很高,提示可能有较高的癌变危险性。     

Wear Mechanisms and Notch Formation of Whisker-Reinforced Alumina and Sialon Ceramic Tools during High-Speed Turning of Inconel 718

Nickel-based alloys, referred to as the most difficult-to-cut materials, pose a great challenge to cutting tool materials due to their excellent high-temperature properties. Ceramic tools have the potential to improve the machinability of these alloys with the advance of toughening mechanisms. In this work, the wear mechanisms of SiC whisker-reinforced alumina and Sialon when high-speed turning Inconel 718 alloy under dry cutting condition were investigated. The results showed that the wear process of Al₂O₃-SiC_w WG300 was dominated by the notch wear, while the flank wear characterized by ridges and grooves perpendicular to the cutting edge was the main wear mode for Sialon SX9. A Ti−enriched belt was found at the boundary of the wear band for both ceramic tools. The SEM inspection and EDS analysis for this belt suggested the trace of diffusion between the workpiece material and tool matrix. As for the notch formation, the periodically adhesive action of the workpiece material at the depth-of-cut line combined with the thermal shock resistance of ceramic tools were considered to account for its formation. In addition, the oxidation of the workpiece material at the depth-of-cut line played a positive role in reducing the adhesive affinity and consequent notch wear.     

BDNF Is Needed for Postnatal Maturation of Basal Forebrain and Neostriatum Cholinergic Neurons In Vivo

Neurotrophins regulate survival, neurite outgrowth, and phenotypic maturation of developing neurons. Brain-derived neurotrophic factor (BDNF) can promote the survival of developing cholinergic forebrain neurons in vitro and reduce their degeneration following injury in adult rats. We investigated the role of endogenous BDNF during postnatal development of these cholinergic neurons by analyzing homozygous BDNF-deficient (−/−) mice and their littermates (+/+, +/−). At P6, the number of choline acetyltransferase- (ChAT) positive neurons in the medial septum was 23% lower in BDNF−/− mice, although their brain and body weight was normal. At P15, control (+/+) littermates had 45% more and 45% larger ChAT-positive neurons and a much denser cholinergic hippocampal innervation than at P6, indicative of maturation of the septohippocampal system. In BDNF−/− mice, the number, size, and ChAT-immunostaining intensity of the cholinergic neurons remained the same between P6 and P15 (few mice survive longer). BDNF−/− mice had about three times more TUNEL-labeled (a marker of apoptosis) cells in the medial septum at P6, consistent with (but not proof of) the possibility that the cholinergic neurons were dying. The cholinergic hippocampal innervation in BDNF−/− mice expanded to a lesser extent than in controls and had reduced levels of acetylcholinesterase staining at P15. The developmental deficits were largely similar in the neostriatum of BDNF−/− mice. These findings suggest that BDNF is critical for postnatal development and maturation of cholinergic forebrain neurons.     

早产儿缺氧缺血性脑病的MRI征像分析

目的:探讨分析早产儿缺氧缺血性脑病的MRI表现及其病理生理。方法:132例临床诊断为新生儿缺氧缺血性脑病的早产儿,常规行T1WI、T2WI、DWI、FLAIR扫描。结果:临床表现均考虑HIE,MRI表现皮层及皮层下出血、深部白质出血、脑室旁出血、脑室内出血、脑室旁软化灶。结论:MRI对早产儿HIE具有特征性表现,对早产儿HIE的早期诊断有重要意义。     

内毒素血症对肝硬化腹水形成机制的研究

目的检测肝硬化腹水患者的血清和腹水中内毒素(Endotoxin,ETX)水平,探讨其与腹水形成的内在联系。方法按照一定标准选取2011年1月至2012年6月本院收治的肝炎肝硬化代偿期患者(对照组)10例、肝炎性和酒精性肝硬化腹水患者80例,包含无明显感染症状的腹水(SA组)50例和有自发性腹膜炎腹水患者(SBP组)30例。按照不同时间段抽取各组患者的清晨空腹外周静脉血和腹水标本进行内毒素含量检测和腹水细菌培养。采用SPSS17.0统计软件处理各组间内毒素含量的差异。结果治疗前50例SA组患者血清、腹水内毒素值分别为(0.108±0.034)U/L、(26.1±3.2)U/L,30例SBP组患者血清、腹水内毒素值为(0.418±0.044)U/L、(1286.1±98.3)U/L。统计结果显示腹水患者的血清内毒素值明显高于对照组患者的(0.025±0.004)U/L(F=201.04,P<0.001);SBP组患者的腹水内毒素值较SA组患者高(t=12.78,P<0.001),不同时间段内毒素水平与腹水病情的严重程度有关(r=7.12,P<0.05)。腹水细菌培养结果阳性率30%,隐匿性感染确实存在于肝硬化腹水患者。结论肝硬化腹水患者血清内毒素升高可能与疾病的严重程度有关,隐匿性感染确实存在于无感染症状的腹水患者中。