Modeling Impacts of Thaw Lakes to Ground Thermal Regime in Northern Alaska

In northern Alaska, the ground is largely underlain by permafrost. Many engineering problems in this region can be attributed to the variations of ground thermal regime. Engineering projects such as construction of gas pipelines must be based on a good understanding of ground thermal regime and its interaction with seasonal climate changes. Numerical modeling is used to simulate a multimedia system with transient heat transfer in this research. The system includes a snow cover on the top, a shallow lake in the middle, and soils beneath the lake. The finite-element method is used for the spatial domain solution, and the finite-difference method is used for the temporal domain solution. The model is applied to three sites in northern Alaska for a nine-month period during the winter of 1995–1996. The result reveals the impacts of thaw lake on the ground thermal regime, the formation of the talik, as well as the formation of ice in the lake. The model is verified against field observations. The difference between the simulated and observed ice thickness is less than 3%.     

The development of imitation crab stick containing chicken breast surimi

Imitation crab stick samples were made from Alaska pollack with Golden treadfin bream surimi (C), Alaska pollack with Golden treadfin bream surimi and spent laying hens breast surimi (T1), Alaska pollack with spent laying hens breast surimi (T2), and Alaska pollack with Golden treadfin bream with mechanically deboning chicken meat (MDCM) (T3). Crude protein was significantly lower in T2 and T3 compared with C and T1. However, crude fat and carbohydrate were not significantly different among the samples during storage periods. pH steadily increased until 2 weeks of storage thereafter pH was decreased in all samples. Lightness (L^∗) and whiteness (W) were significantly lower in T3 than those of other samples. In fatty acid composition, the amount of polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was higher than other fatty acids in all samples at 0 week of storage period. TBARS (thiobarbituric acid reactive substances) value was highest in control sample compared with other samples. In sensory evaluation, color was the highest in C than other samples, whereas T3 was lowest in color than those of other samples. Overall acceptability was significantly highest in T1 compared with other samples during the storage periods.     

Laboratory Study on Dispersant Effectiveness in Alaskan Seawater

The objective of this project was to test dispersant effectiveness in the laboratory under conditions relevant to Prince William Sound (PWS), Alaska. Two laboratory testing methods were used to compare a range of test conditions and dispersant to oil ratios (DORs) using PWS seawater at 8°C, Alaska North Slope (ANS) crude oil, and Corexit 9500. Three DORs were tested, 1:10, 1:20, and 1:50. It was found that in most cases, the dispersant effectiveness was directly proportional to the DOR. For each DOR, dispersant effectiveness was measured at four contact times (time between dispersant application to a spill and start of mixing) and five weathering times (time between oil spill and dispersant application). Corexit 9500 dispersed ANS crude oil at 8°C in PWS seawater to differing degrees, depending on the test conditions. The results indicated that, in general, the greatest dispersion occurred when the weathering time was minimized and a short contact time was provided.     

Distribution, speciation, and transport of mercury in stream-sediment, stream-water, and fish collected near abandoned mercury mines in southwestern Alaska, USA

Concentrations of total Hg, Hg (II), and methylmercury were measured in stream-sediment, stream-water, and fish collected downstream from abandoned mercury mines in southwestern Alaska to evaluate environmental effects to surrounding ecosystems. These mines are found in a broad belt covering several tens of thousands of square kilometers, primarily in the Kuskokwim River basin. Mercury ore is dominantly cinnabar (HgS), but elemental mercury (Hg degrees) is present in ore at one mine and near retorts and in streams at several mine sites. Approximately 1400 t of mercury have been produced from the region, which is approximately 99% of all mercury produced from Alaska. These mines are not presently operating because of low prices and low demand for mercury. Stream-sediment samples collected downstream from the mines contain as much as 5500 microg/g Hg. Such high Hg concentrations are related to the abundance of cinnabar, which is highly resistant to physical and chemical weathering, and is visible in streams below mine sites. Although total Hg concentrations in the stream-sediment samples collected near mines are high, Hg speciation data indicate that concentrations of Hg (II) are generally less than 5%, and methylmercury concentrations are less than 1% of the total Hg. Stream waters below the mines are neutral to slightly alkaline (pH 6.8-8.4), which is a result of the insolubility of cinnabar and the lack of acid-generating minerals such as pyrite in the deposits. Unfiltered stream-water samples collected below the mines generally contain 500-2500 ng/l Hg; whereas, corresponding stream-water samples filtered through a 0.45-microm membrane contain less than 50 ng/l Hg. These stream-water results indicate that most of the Hg transported downstream from the mines is as finely-suspended material rather than dissolved Hg. Mercury speciation data show that concentrations of Hg (II) and methylmercury in stream-water samples are typically less than 22 ng/l, and generally less than 5% of the total Hg. Muscle samples of fish collected downstream from mines contain as much as 620 ng/g Hg (wet wt.), of which 90-100% is methylmercury. Although these Hg concentrations are several times higher than that in fish collected from regional baseline sites, the concentration of Hg in fish is below the 1000 ng/g action level for edible fish established by the US Food and Drug Administration (FDA). Salmon contain less than 100 ng/g Hg, which are among the lowest Hg contents observed for fish in the study, and well below the FDA action level.     

SEAMONSTER: A demonstration sensor web operating in virtual globes

A sensor web is a collection of heterogeneous sensors which autonomously reacts to the observed environment. The SouthEast Alaska MOnitoring Network for Science, Technology, Education, and Research (SEAMONSTER) project has implemented a sensor web in partially glaciated watersheds near Juneau, Alaska, on the edge of the Juneau Icefield. By coupling the SEAMONSTER sensor web with digital earth technologies the scientific utility, education and public outreach efforts, and sensor web management of the project all greatly benefit. This paper describes the scientific motivation for a sensor web, the technology developed to implement the sensor web, the software developed to couple the sensor web with digital earth technologies, and demonstrates the SEAMONSTER sensor web in a digital earth framework.     

鳕鱼骨汤的熬制及风味物质释放规律

本文以鳕鱼骨为研究对象,对高压熬制鳕鱼骨汤的最佳熬制工艺参数进行了研究,分析了高压鱼汤在熬制15、30、45、60、75、90、105和120 min过程中的风味变化规律,对比分析了常压和高压鳕鱼骨汤的风味物质差异。研究结果表明,高压熬制最佳工艺条件为料水比1:2、温度110℃、时间2 h,蛋白溶出率为(7.49±0.26) g/100 g鱼骨;高压鱼骨汤在熬制过程中,多肽类物质在30 min后开始稳步地溶出,最终稳定在2.00 mg/L;3种核苷酸在90~105 min的区间内浓度达到最高,有机酸类物质中乳酸含量在90min时达到最高,为67.91mg/L;GC-MS分析结果表明醛类、酮类是构成鱼骨汤风味的主要物质;高压鱼骨汤中的蛋白质溶出率、多肽和5’-AMP的含量分别是常压鱼骨汤的1.54、1.20和4.87倍。在常压鱼骨汤和高压鱼骨汤中分别检测到33和37种挥发性风味物质,同时在高压条件下产生了更多的醛类、酮类物质,具有更好的风味。     

Application of recombinant chum salmon cystatin to Alaska pollock (Theragra chalcogramma) surimi to prevent gel weakening

ABSTRACT:  Recombinant chum salmon cystatin (RC) expressed in Saccharomyces cerevisiae was purified by His-select nickel affinity chromatography. The specific inhibitory activities of RC against papain and cathepsin L were 7.45 and 10.24 U/mg, respectively. RC was stable over pH 5.0 to 7.0 and at temperature below 65 °C. RC was used to prevent the gel weakening of Alaska pollock surimi. RC at 100 μg/g showed the highest inhibitory activity against the autolysis of surimi based on the analysis of TCA-soluble peptides. As the concentration of RC increased, both the breaking force and deformation of modori gel greatly increased ( P < 0.05). The addition of RC resulted in less expressible drip, which coincided with the increase of whiteness. More myosin heavy chain (MHC) was retained as the addition of RC increased. Therefore, RC could prevent the degradation of proteins in Alaska pollock surimi and was better than egg white (EW). Thus, RC could be applied to Alaska pollock surimi to prevent gel weakening and RC at 100 μg/g was the optimal concentration.     

Combined Effect of Loading and Cold Temperature on the Stiffness of Glass Fiber Composites

Because of the short construction season and cold winters in Alaska, the prestressed concrete decked bulb-tee bridge system is very popular. However, the concrete deck is an integral part of the bridge superstructure and cannot be easily replaced when it deteriorates. Obviously, there is merit in combining durable “premanufactured” fiber-reinforced polymer (FRP) composite deck with stiffer prestressed concrete girders in cold regions. However, the effects of long-term exposure to extreme temperature variations and various moisture conditions typical of cold regions on the performance of FRP composite materials are not fully understood. This paper summarizes the combined effect of low-temperature and deformation strain levels on the longitudinal modulus of glass fiber-reinforced polymer (GFRP) samples. The modulus of elasticity of GFRP laminate coupons was tested at various temperatures down to ?31 °F (?35°C) by temporarily subjecting the samples to three strain levels of 1,000, 2,000, or 3,000 microstrains. Both biaxial and uniaxial samples subjected to a deformation of 1,000 microstrains showed an increase in stiffness when tested at increasingly colder temperatures, and no noticeable change in stiffness was seen when the samples were retested after being equilibrated to room temperature. However, samples subjected to a predetermined elevated strain level did show significant stiffness degradation after room temperature equilibration. The degree of degradation was noticeably larger for samples subjected to the low temperatures than for control samples that were subjected to the equivalent number of cycles at room temperature. It was also noted that the degradation due to load cycles or temperature coupled with load cycles was noticeably less for uniaxial samples than for biaxial samples.     

深海鱼油中脂肪酸的柱前衍生-高效液相色谱串联质谱分析

用1-2-(对甲苯磺酸酯)乙基-2-苯基咪唑4,5-f9,10-菲(TSEPIP)作为柱前荧光衍生试剂,在EclipseXDB-C8(4.6×150mm,5μm,Agilent)反相色谱柱上,采用梯度洗脱在检测波长为380nm(激发波长为260nm)的条件下,实现了阿拉斯加深海鱼油中饱和脂肪酸含量的外标法定量测定。26种饱和脂肪酸的线性范围是200.0pmol～48.83fmol,线性相关系数均大于0.9996,检测限为3.824～47.13fmol(信噪比为3:1测得,S/N3:1)。经柱后串联质谱大气压化学电离源(APCI)正离子模式实现了各种饱和与不饱和脂肪酸衍生物的质谱鉴定,进而通过峰面积归一化法得出了所有饱和与不饱和脂肪酸的相对含量。结果表明,深海鱼油主要含有C12～C22的脂肪酸,共鉴定出25种脂肪酸,其中不饱和脂肪酸含量占69.71%(峰面积百分比,下同),特别是具有重要生理作用的多不饱和脂肪酸,如C20:5:5,8,11,14,17-二十碳五烯酸(5,8,11,14,17-eicosapentaenoicacid,EPA,16.62%),C22:6:2,5,8,11,14,17-二十二碳六烯酸(2,5,8,11,14,17-docosahexenoicacid,DHA,12.31%)。