Impact of Freeze–Thaw Cycles on the Long-Term Performance of Concrete Pavement and Related Improvement Measures: A Review

Freeze–thaw damage is one of the most severe threats to the long-term performance of concrete pavement in cold regions. Currently, the freeze–thaw deterioration mechanism of concrete pavement has not been fully understood. This study summarizes the significant findings of concrete pavement freeze–thaw durability performance, identifies existing knowledge gaps, and proposes future research needs. The concrete material deterioration mechanism under freeze–thaw cycles is first critically reviewed. Current deterioration theories mainly include the hydrostatic pressure hypothesis, osmolarity, and salt crystallization pressure hypothesis. The critical saturation degree has been proposed to depict the influence of internal saturation on freeze–thaw damage development. Meanwhile, the influence of pore solution salinity on freeze–thaw damage level has not been widely investigated. Additionally, the deterioration mechanism of the typical D-cracking that occurs in concrete pavement has not been fully understood. Following this, we investigate the coupling effect between freeze–thaw and other loading or environmental factors. It is found that external loading can accelerate the development of freeze–thaw damage, and the acceleration becomes more evident under higher stress levels. Further, deicing salts can interact with concrete during freeze–thaw cycles, generating internal pores or leading to crystalline expansion pressure. Specifically, freeze–thaw development can be mitigated under relatively low ion concentration due to increased frozen points. The interactive mechanism between external loading, environmental ions, and freeze–thaw cycles has not been fully understood. Finally, the mitigation protocols to enhance frost resistance of concrete pavement are reviewed. Besides the widely used air-entraining process, the freeze–thaw durability of concrete can also be enhanced by using fiber reinforcement, pozzolanic materials, surface strengthening, Super Absorbent Polymers (SAPs), and Phase Change Materials. This study serves as a solid base of information to understand how to enhance the freeze–thaw durability of concrete pavement.     

Cerebrovascular responses to somatomotor stimulation in Parkinson’s disease: A multivariate analysis

Parkinson’s disease (PD) is a common neurodegenerative disorder, yet little is known about cerebral haemodynamics in this patient population. Previous studies assessing dynamic cerebral autoregulation (dCA), neurovascular coupling (NVC) and vasomotor reactivity (VMR) have yielded conflicting findings. By using multi-variate modelling, we aimed to determine whether cerebral blood flow (CBF) regulation is impaired in PD patients.55 healthy controls (HC) and 49 PD patients were recruited. PD subjects underwent a second recording following a period of abstinence from their anti-Parkinsonian medication. Continuous bilateral transcranial Doppler in the middle cerebral arteries, beat-to-beat mean arterial blood pressure (MAP; Finapres), heart rate (HR; electrocardiogram), and end-tidal CO₂ (EtCO₂; capnography) were measured. After a 5-min baseline period, a passive motor paradigm comprising 60 s of elbow flexion was performed. Multi-variate modelling quantified the contributions of MAP, ETCO₂ and neural stimulation to changes in CBF velocity (CBFV). dCA, VMR and NVC were quantified to assess the integrity of CBF regulation.Neural stimulation was the dominant input. dCA, NVC and VMR were all found to be impaired in the PD population relative to HC (p < 0.01, p = 0.04, p < 0.01, respectively). Our data suggest PD may be associated with depressed CBF regulation. This warrants further assessment using different neural stimuli.     

多肽合成中"困难序列"的缩合研究进展

化学学科发展至今拥有极强的能力来获得高的合成效率，但是在多肽合成中“困难序列”的存在仍然成为成功缩合的巨大挑战。本文综述了影响多肽缩合效率的因素以及提高“困难序列”缩合效率的有效方法。所述方法均简便易行，适用于多肽的固相合成或液相合成。     

Herbimycin A Suppresses the Reduction of Gap-junctional Intercellular Communication Induced by Tumor-promoting Phorbol Ester in 3T3-L1 Cells

We have examined the suppressive effect of herbimycin A on the reduction of gap-junctional Intercellular communication that is induced by a tumor-promoting phorbol ester in 3T3-L1 cells. Most cells in growth arrest participated in dye-coupling, as evaluated by the transfer between cells of a fluorescent dye (Lucifer Yellow CH). Treatment of cells with 0.25 μg/ml herbimycin A slightly enhanced the dye-coupling. This enhancement required treatment for periods as long as 24 h. Addition of 100 ng/ml 12-O-tetradecanoylphorbol-13-acetate (TPA) caused a rapid reduction of dye-coupling. However, addition of TPA did not suppress dye-coupling in cells pretreated for more than 24 h with herbimycin A. Pretreatment of cells for less than 6 h with herbimycin A did not suppress the TPA-induced reduction of dye-coupling. These results suggest that herbimycin A suppresses the reduction of gap-junctional intercellular communication that is induced by TPA through enhancement of the ability of the cells to participate in gap-junctional intercellular communication     

不同给氧方式在无痛胃镜中的应用

目的探讨无痛胃镜检查中的最佳给氧方式.方法 200例无痛胃镜病人,采用芬太尼与异丙酚复合静脉麻醉,根据给氧方式不同随机分为4组：Ⅰ组,静脉麻醉前后面罩均给氧,氧流量4～5L/min;Ⅱ组,鼻导管给氧,氧流量 4～ 5L/min;Ⅲ组,不给氧,但SpO2下降至93%及以下时用面罩给氧;Ⅳ组,高频喷射通气,驱动压力1kg/cm^2,频率100次/min.记录病人麻醉前,麻醉后2,4,6,8,10min时的呼吸次数及SpO2.结果麻醉后2,4,6min所有病人呼吸频率均较麻醉前显著降低（ P ＜0.05）,8min后呼吸频率逐渐恢复至麻醉前水平.Ⅱ组SpO2麻醉后2min有一明显降低（ P ＜0.05）,50例中有9例需改行面罩给氧.Ⅲ组SpO2在2,4,6,8min均较麻醉前明显降低（ P ＜0.05）,50例中有23例病人因SpO2低于93%而需改为面罩给氧.Ⅰ、Ⅳ组病人麻醉前后SpO2均在正常范围,无显著性差异（ P ＞0.05）.结论无痛胃镜检查,不给氧不可取,用鼻导管给氧存在一定风险,而用麻醉机面罩给氧和进行高频喷射通气给氧是安全有效的方法.     

叶酸-蒜酶缀合物的合成及联合蒜氨酸原位抑制肿瘤细胞增殖作用

合成叶酸-蒜酶缀合物(FA-Alliinase),采用宫颈癌HeLa细胞考察其对肿瘤细胞的靶向性和抑制肿瘤生长活性。采用两种方法合成叶酸-蒜酶缀合物FA-AlliinaseⅠ和FA-AlliinaseⅡ,测得两种缀合物的偶联比分别为12和31,选择高偶联比的FA-AlliinaseⅡ,对其结构进行初步的表征。高效液相色谱法测得FA-AlliinaseⅡ有约50%的蒜酶活力;激光共聚焦及流式细胞仪观察到FA-AlliinaseⅡ对HeLa细胞具有一定的靶向性,MTT法测得FA-AlliinaseⅡ联合蒜氨酸后对HeLa细胞增殖有抑制作用,以蒜氨酸计IC₅₀为(127.6±2.3)μmol/L。该研究为类前药叶酸-蒜酶缀合物的合成优化提供了较为直接的评价方法。     

无机陶瓷膜微滤耦合超声澄清痹通药酒提取液的研究

目的 研究无机陶瓷膜微滤耦合超声技术在痹通药酒澄清过滤中的应用。方法 以膜渗透通量、膜污染阻力分布等为指标,考察间歇超声、连续超声与未耦合超声在痹通药酒澄清滤过中的差异,进而对操作条件进行优化研究。结果 连续超声可显著增强膜的渗透性能,渗透通量高达173 L/(m2·h),通量提高率31.6%,同时还能有效降低膜污染阻力,尤其对膜表面沉积层,降幅达50%以上。一定范围内,超声对膜过程的强化与操作压力呈正比,与操作温度呈反比。结论 陶瓷膜微滤过程耦合超声技术是一种安全有效的膜分离手段。     

耦合剂应用于聚焦超声治疗慢性宫颈炎的疗效

目的探讨超声治疗用耦合剂介质在聚焦超声治疗慢性宫颈炎时的作用.方法将344例慢性宫颈炎患者分为蒸馏水介质组161例和超声治疗用耦合剂介质组183例,比较两组治疗方法对不同宫颈糜烂类型的治疗效果、治疗时间及不良反应.结果两组的总有效率无显著差异,但超声治疗用耦合剂介质组治疗中、重度宫颈糜烂的治愈率显著高于蒸馏水介质组82.43% VS 67.74%,60.94% VS 40.35%且前者治疗时间显著低于后者;两组不良反应没有显著差异.结论超声治疗用耦合剂能显著提高聚焦超声治疗中、重度宫颈糜烂的治愈率,缩短操作时间.     

First-Principles Study of Silicon–Tin Alloys as a High-Temperature Thermoelectric Material

Silicon–germanium (SiGe) alloys have sparked a great deal of attention due to their exceptional high-temperature thermoelectric properties. Significant effort has been expended in the quest for high-temperature thermoelectric materials. Combining density functional theory and electron–phonon coupling theory, it was discovered that silicon–tin (SiSn) alloys have remarkable high-temperature thermoelectric performance. SiSn alloys have a figure of merit above 2.0 at 800 K, resulting from their high conduction band convergence and low lattice thermal conductivity. Further evaluations reveal that Si_0.75Sn_0.25 is the best choice for developing the optimum ratio as a thermoelectric material. These findings will provide a basis for further studies on SiSn alloys as a potential new class of high-performance thermoelectric materials.     

Experimental and Numerical Study on the Penetration Performance of a Shaped Charge

In guided ammunition, because a shaped energy jet warhead is located behind the control cabin (including the guidance cabin, the steering gear cabin, and the flight control cabin), the penetration order of a shaped energy jet is the control cabin and the target plate. In order to obtain maximum penetration depth by a shaped energy jet into a Q235 steel plate, the penetration performance of shaped energy jets was studied by numerical simulation and experimental verification. Firstly, the penetration performance of a warhead under different conditions at a certain explosion height is studied, which is the penetration performance of a Q235 steel plate with and without the control cabin. Secondly, the numerical simulation results are verified by experimental method. The numerical simulation and experimental results showed that, after penetration of the shaped energy jet warhead into the control cabin, it continued to penetrate the 20 mm-thick Q235 steel plate. At a certain explosion height, the maximum penetration depth of the shaped energy jet warhead into the Q235 steel plate was about 80 mm. Alongside the numerical simulation and experiment, the armor-breaking process of the shaped charge jet was analyzed theoretically. The results show that when the shaped energy jet warhead is located behind the control cabin, although the control cabin will have a certain impact on the penetration ability of shaped energy jet, the penetration performance of the residual jet still has the ability to penetrate light armor.