Small lateral air pressure gradients generated by a large chamber system have a strong effect on CO2 transport in soil

Gas transport in soils is usually assumed to be purely diffusive, although several studies have shown that non-diffusive processes can significantly enhance soil gas transport. These processes include barometric air pressure changes, wind-induced pressure pumping and static air pressure fields generated by wind interacting with obstacles. The associated pressure gradients in the soil can cause advective gas fluxes that are much larger than diffusive fluxes. However, the contributions of the respective transport processes are difficult to separate. We developed a large chamber system to simulate pressure fields and investigate their influence on soil gas transport. The chamber consists of four subspaces in which pressure is regulated by fans that blow air in or out of the chamber. With this setup, we conducted experiments with oscillating and static pressure fields. CO₂ concentrations were measured along two soil profiles beneath the chamber. We found a significant relationship between static lateral pressure gradients and the change in the CO₂ profiles (R² = 0.53; p-value <2e-16). Even small pressure gradients between −1 and 1 Pa relative to ambient pressure resulted in an increase or decrease in CO₂ concentrations of 8% on average in the upper soil, indicating advective flow of air in the pore space. Positive pressure gradients resulted in decreasing, negative pressure gradients in increasing CO₂ concentrations. The concentration changes were probably caused by an advective flow field in the soil beneath the chamber generated by the pressure gradients. No effect of oscillating pressure fields was observed in this study. The results indicate that static lateral pressure gradients have a substantial impact on soil gas transport and therefore are an important driver of gas exchange between soil and atmosphere. Lateral pressure gradients in a comparable range can be induced under windy conditions when wind interacts with terrain features. They can also be caused by chambers used for flux measurements at high wind speed or by fans used for head-space mixing within the chambers, which yields biased flux estimates.     

人造板甲醛释放量不同检测方法之间的相关性分析

甲醛释放量是评价木制品对环境和人体健康是否有危害的重要指标,针对当前我国、美国、欧盟、日本等国内外广泛使用的甲醛释放量测定方法,通过进行对比和分析建立数学相关性方程,为生产企业提高检测效率和降低检测成本,保障出口木制品的质量提供参考。     

一个测定呼吸速率装置的研究

[目的]为了设计可以测定植物整体或组织、器官呼吸作用的实验装置。[方法]改进LI-6400便携式测定系统的同化室,测定时将植株放入同化室内,通过测定单位时间内同化室内二氧化碳的增加量来定量测量呼吸作用。[结果]通过公式,可以计算整棵植株的呼吸速率。[结论]这个简便的装置可准确地测量整棵植株或组织、器官的呼吸速率。     

覆膜玉米不同生育期土壤酶活性对大气CO2浓度升高的响应

为探讨旱区覆膜玉米农田土壤酶活性对未来气候变化的响应,在田间条件下通过改进的开顶式气室(OTC)系统自动控制大气CO_2浓度,设置自然大气CO_2浓度(CK)、OTC对照(OTC)、OTC系统自动控制CO_2浓度(700μmol·mol~(-1),OTC+CO_2)3个处理,研究了旱区覆膜高产栽培春玉米播前、六叶期(V6)、十二叶期(V12)、吐丝期(R1)、乳熟期(R3)及完熟期(R6)土壤脲酶、碱性磷酸酶、蔗糖酶及过氧化氢酶活性对大气CO_2浓度升高的响应特征。研究发现:OTC处理条件下,土壤碱性磷酸酶活性相比CK在V12期降低8.80%(P0.05),而在R6期提高8.95%(P0.05);蔗糖酶活性在播前、V6、R1期降低12.65%～21.43%(P0.05),R3期升高17.50%(P0.05);过氧化氢酶活性在V12、R1、R6期均显著降低。大气CO_2浓度升高对玉米各生育期土壤脲酶活性均无显著影响;使R1、R6期碱性磷酸酶活性降低8.74%和6.39%(P0.05);使V6、R3期蔗糖酶活性升高30.18%和18.37%(P0.05);此外,增加了V12期过氧化氢酶活性,而降低了R3期过氧化氢酶活性。结果表明:当前旱作覆膜高产栽培模式下,大气CO_2浓度升高对春玉米农田土壤酶活性的影响因作物生育期和酶种类不同而异;土壤酶活性对OTC及大气CO_2浓度升高的响应程度不一,在当前试验条件下,OTC对土壤酶活性的影响较大气CO_2浓度升高更为显著。     

PWM间歇喷雾变量喷施系统中的压力损失和液压冲击

在PWM间歇喷雾式变量喷施系统中,流量变化会引起喷杆各管路中的压力损失的变化,电磁阀的快速启闭会在管路中形成液压冲击,致使各喷头的实际喷雾压力发生波动,导致其喷施流量和雾化特性出现畸变。为揭示其管路压力损失的变化特性和液压冲击特性,构建了一套PWM间歇喷雾式变量喷施系统,并对其进行了流体动力学分析,确定了不同喷雾流量下的管路药液流态,建立了压力损失和液压冲击的计算模型,分析了0.3 MPa设定喷杆压力下的管路压力损失变化范围和液压冲击幅度,并进行了实际试验测试。结果表明:在0.3 MPa设定喷杆压力下,同一喷头前端管路的压力损失的变化幅度可达140 kPa,不同喷头间的实际喷雾压力差异可达25 kPa,由于电磁阀快速启闭而引起的液压冲击幅值可达170 k Pa。     

阻燃杨木胶合板挥发性有机化合物释放研究

选取四种品牌四种厚度阻燃杨木胶合板,待其释放稳定（第28天）,采用小型环境舱采集其挥发性有机化合物（VOCs）,并结合气相色谱-质谱法,分析挥发性有机化合物种类和含量.实验结果表明：不同品牌阻燃杨木胶合板总挥发性有机化合物（TVOC）释放量在50.14μg/m3 ～ 248.92μg/m3之间;各个板材VOCs释放量和检出物不完全相同,单个板材检出物种类最高为36种;芳香类和烃类化合物质量浓度之和占挥发性有机化合物总质量浓度的55.10％～85.72％;同时还捡出醛类、酮类和酯类等其他挥发性有机化合物;经过磷-氮-硼系阻燃剂处理的板材VOCs释放量比磷-氮系阻燃剂处理板材高;同种品牌阻燃杨木胶合板随厚度增加TVOC释放量呈增加趋势.     

Effects of B-trichothecenes on luminal glucose transport across the isolated jejunal epithelium of broiler chickens

Trichothecenes are closely-related sesquiterpenoids (ring structure) with a 12, 13 epoxy ring and a variable number of hydroxyl, acetyl or other substituents. In chickens, D-glucose and amino acid absorption occurs via carrier-mediated transport. Recently, it has been observed that deoxynivalenol (DON) alters the gut function and impairs glucose and amino acid transport in chickens. The purpose of this work was to determine the effects of different B-trichothecenes [DON, Nivalenol (NIV), 15-Ac-DON and Fusarenon X (FUS X)] on intestinal carrier-mediated sodium co-transport of D-glucose in the small intestine of broiler chickens. Intestinal transport was determined by changes in the short-circuit current (Isc), proportional to ion transmembrane flux, in the middle segment of the jejunum of broilers with the Ussing chamber technique. D-glucose produced an increase of the Isc, and this effect was reverted by different B-trichothecene mycotoxins, indicating that the glucose induced Isc was altered by B-trichothecenes. The addition of glucose after pre-incubation of the tissues with B-trichothecenes had no effect (p > 0.05) on the Isc, suggesting that B-trichothecenes afflicted the Na(+)-D-glucose co-transport. However, FUX had no obvious effect on the measured parameters. It could be concluded from the present study that the glucose co-transporter activity appears to be more sensitive to DON, NIV and 15-Ac-DON suppression than by FUS X in the jejunum of broilers.     

Heart rate variability parameters as markers of the adaptation to a sealed environment (a hypoxic normobaric chamber) in the horse

Simulated hypoxic normobaric devices have been used in human beings in order to enhance endurance capacity. These devices are sealed chambers where the athletes are supposed to stay for at least 6–8 hr daily. The current research assesses the changes in time‐domain, spectral and non‐geometrical heart rate variability (HRV) parameters in 6 horses subjected to progressive duration periods inside of a hermetically sealed chamber. It was pursued, firstly to evaluate the intensity of the stress experienced by the animals and secondly to elucidate whether the horses might require an acclimation period before implementation of hypoxic conditions. HRV parameters were monitored for 6 days: day 0 (6‐hr duration; in paddocks; basal conditions), and days 1, 2, 3, 4 and 5 (1, 2, 3, 4 and 6 hr inside the chamber every day respectively). During day 1 and during the first hours of days 2 and 3, compared to day 0, horses presented increased HR and SDHR values and decreased RR interval duration. SD1 values decreased on some hours of days 2 and 3, but differences with day 0 were not found on day 1. Increased SDNN, RMSSD, SD1 and SD2 values were observed on days 4 and 5. These results showed an activation of the sympathetic activity together with an attenuation of the parasympathetic activity during the days 1 to 3. Increased parasympathetic activity was found only during the first hours of days 4 and 5. Spectral parameters experienced minor variations, with increased LF_peak and LF% during some hours of days 4 and 5. In conclusion, at least 3 days are needed to adapt the horse to a sealed environment before starting to subject the animals to hypoxic conditions. When the horses were acclimatized, however, a minor stress was detected with they spent more than 4 hr inside of the chamber.     

Anesthetic concentrations in enclosed chambers using an innovative delivery device

OBJECTIVE: To quantify factors influencing anesthetic concentration when an innovative anesthetic delivery device (vapor wand) was used with enclosed chambers. STUDY DESIGN: Randomized study. METHODS: Two experimental chambers (57.4 and 171 L) were constructed. Anesthetic volumes necessary to reach a target concentration of 3% or 5% isoflurane with complete vaporization were calculated for each chamber. After centering the distal end of the vapor wand and multi-orifice sampler, each chamber was sealed. Air (450 mL) was cycled through the vapor wand in a to-and-fro fashion with an electric, modified air pump at either 20 or 40 cycles minute(-1). Samples taken at 30-second intervals were analyzed for isoflurane concentration. Times to reach 2.8% isoflurane concentration were compared for eight treatment combinations replicated three times. Curves were constructed to display the rate of rise to endpoint concentration. Analysis of variance was applied to the data. RESULTS: Chamber size, pump stroke rate, and target isoflurane concentration all affected time to reach 2.8%, and their three-way interaction was statistically significant (p < 0.05). Generally time to 2.8% was less with small chambers, more rapid pumping and a target concentration of 5%. CONCLUSIONS AND CLINICAL RELEVANCE: When a wild or aggressive animal is presented for clinical veterinary care, introduction of a vapor wand into its cage offers a safer, more convenient, and less stressful alternative for anesthesia than transfer to an induction chamber. By quantifying factors affecting the rate of rise of anesthetic concentration with its use in experimental chambers, this study should promote greater safety and predictability when used clinically. This information will be useful when anesthetic induction needs to be hastened or delayed depending on the responses of the patient and the clinical judgment of the anesthetist.     

高压脉冲电场(PEF)处理装置内温度分布的模型试验研究

该文通过模型试验方法测量了高压脉冲电场（ＰＥＦ）处理装置内的温度分布。在静态情况下,从处理装置的中心孔到电极间的温度分布呈指数衰减。在流动状态时,温度分布不均匀,在处理装置内有高温度点。