Paleoenvironmental interpretation of late glacial and post-glacial fossil marine molluscs, eureka sound, Canadian Arctic Archipelago

A total of 5065 specimens (5018 valves of bivalve and 47 gastropod shells) have been identified and classified into 27 species from 55 samples collected from raised glaciomarine and estuarine sediments, and glacial tills. The bivalves Hiatella arctica, Mya truncate, Astarte borealis, and Serripes groenlandicus are the most common species. Our samples record the dominance of infaunal suspension-feeders that are most abundant on soft substrates typically occurring in nearshore environments. The dominance of bivalves with respect to gastropods reflects an averaged record of the fossil assemblages inhabiting the high latitude nearshore environments. Six unique associations, which are comparable to the composition of modern communities inhabiting in fiords and on continental shelf from Canadian high arctic, and three distinctive taxa groups (deposit feeders, suspension-feeders, and rare taxa) are recognized by cluster analysis and Multidimensional Scaling conducted on presence-absence data. The trophic composition of paleocommunities in this study is as follows: suspension-feeders > deposit feeders > carnivores > browsers. The occurrence of Mya pseudoarenaria in fossil assemblages indicates an age of the fossils around early Holocene. Most of the samples are not substantially transported nor significantly reworked. Shell disarticulation and fragmentation can result from sea ice scouring of the seafloor and the development of permafrost in raised marine sediments. The degree of shell disarticulation for the four most common taxa is generally low which likely reflects high sedimentation rates and rapid burial in nearshore environments, especially those from glaciomarine silts and estuarine deposits. Four common species exhibit different preservation potential based the degree of fragmentation and disarticulation (Serripes < Mya < Hiatella < Astarte). Shells with high (or low) degree of fragmentation for single species (i.e. Hiatella) also correspond to different energy conditions of the associated sediments facies from which the shells are recovered. The general absence of strongly bioeroded or encrusted shells among samples suggests rapid burial of the shells with only limited exposure on the sediment surface, or the absence of grazing, boring or encrusting taxa in the environment that is dominated by infaunal habit of most of the taxa represented in the shell assemblages. Four taphofacies are recognized by cluster analysis on the basis of four taphonomic variables (fragmentation, corrasion, bioerosion, and encrustation) characterized by poor preservation, fair preservation, fair-good preservation, and fair preservation with poor corrasion respectively. Faunal succession and paleo-marine environments during the deglaciation in early Holocene are reconstructed from the seven sedimentation facies (glacial, beaches, shallow marine, proglacial, shallow marine or estuarine - pebbly sand and gravel with algal debris, shallow marine or estuarine - pebbly silt with algal debris, shallow marine or estuarine - interbedded silt and sand)

Thermal Performance and Moisture Accumulation of Mechanical Pipe Insulation Systems Operating at Below Ambient Temperature in Wet Conditions with Moisture Ingress

When pipes are used for chilled water, glycol brines, refrigerants, and other chilled fluids, energy must be spent to compensate for heat gains through the wall of the pipes. Higher fluid temperature at the point of use decreases the efficiency of the end-use heat exchangers and increases the parasitic energy consumption. Mechanical pipe insulation systems are often used to limit the heat gains and save energy in commercial buildings. Pipe insulation systems play an important role for the health of the occupied space. When a chilled pipe is uninsulated or inadequately insulated, condensation might occur and water will drip onto other building surfaces possibly causing mold growth. The critical issue with cold pipes is that the temperature difference between the pipe and its surrounding ambient air drives water vapor inside the insulation system and condensation commonly occurs when the water vapor comes in contact the chilled pipe surface. This paper experimentally studies this issue for pipe insulation systems operating at below ambient temperature. The moisture content and the associated thermal conductivity of several pipe insulation systems were measured under various wet condensing conditions with moisture ingress. Accelerated type tests in laboratory highlighted the propensity of moisture accumulation in the insulation systems with cylindrical configuration and with split longitudinal joints. The moisture accumulation rate was measured and the apparent thermal conductivity increased significantly in a 60 days period when water vapor entered a pipe insulation syste

Design of an Experimental Facility for Frost Growth Study in Microchannel Heat Exchangers

This report focused on the new experimental methodology developed to investigate the frost and defrost thermal hydraulic performances of louvered folded fin microchannel heat exchangers under initial frost cycle, defrost cycle, and subsequent re-frost cycles. The required laboratory conditions are 35/33 &degF dry-/wet-bulb temperature, with the air velocity around 100 ~ 300 fpm. In the air side, the required conditions were reached by a humidification, a cooling and a re-heating process with a fan, a refrigeration coil, a humidifier and a re-heating coil. In the refrigerant side, the required inlet coolant temperature was controlled by an automatically controlled heater and a plate heat exchanger connected with the chiller. The frost accumulation was measured by a precision scale for frost weight, and a videoscope for frost thickness. Uncertainties on U and hout were investigated based on both precision and bias uncertainties.Mechanical & Aerospace Engineerin

Thermal Performance of Mechanical Pipe Insulation Systems at Below-ambient Temperature

Mechanical pipe insulation systems are commonly applied to cold piping surfaces in most industrial and commercial buildings in order to limit the heat losses and prevent water vapor condensation on the pipe exterior surfaces. Due to the fact that the surface temperature of these pipelines is normally below the ambient dew point temperature, water vapor diffuses inside the pipe insulation systems often condenses when it reaches the pipe exterior surfaces. The water droplets accumulated in the pipe insulation system increase its overall thermal conductivity by thermal bridging the cells or the fibers of the insulation material. The moisture ingress into pipe insulation threatens the thermal performance and the overall efficiency of the building mechanical system. The main objective of this research was to investigate the effects of water vapor ingress on the thermal conductivity of pipe insulation systems. A critical review of the state of the art literature in this field was included to clarify the similarities and differences on the apparent thermal conductivity of pipe insulation systems and flat slabs. A new experimental methodology was developed to isolate and quantify the effect of water vapor ingress to the pipe insulation systems. Seven fibrous and ten closed-cell pipe insulation systems were tested on the novel experimental apparatus under dry and wet, condensing conditions. Under dry condition, the apparent thermal conductivity was observed linearly varied with insulation mean temperature, and the presence of joint sealant may increase the apparent thermal conductivity by 15%. During moisture test, results showed that the moisture diffusion mechanism were different in fibrous and closed-cell pipe insulation systems. Compared to closed-cell, fibrous pipe insulation system behaved more sensitive to the moisture content and the thermal conductivity increased dramatically due to the formation of more thermal bridging and preferential paths. An analytical model was developed based on the diffusion mechanism to predict the moisture accumulation and the associated penalization of the apparent thermal conductivity in different pipe insulation systems operating below ambient room temperature. The model was validated with the experimental results and the data reported in the literature on the thermal conductivity ratio with different moisture content. The differences were within 10% for closed-cell pipe insulation, and within 15% for fibrous pipe insulation systems.Mechanical Engineerin

Moisture Accumulation and Its Impact on the Thermal Performance of Pipe Insulation for Chilled Water Pipes in High Performance Buildings

Mechanical pipe insulation systems are commonly applied to cold piping surfaces in most industrial and commercial buildings in order to limit the heat losses and prevent water vapor condensation on the pipe exterior surfaces. Due to the fact that the surface temperature of these pipelines is normally below the ambient dew point temperature, water vapor diffuses inside the pipe insulation systems and often condenses when it reaches the pipe exterior surfaces. The water droplets accumulated in the pipe insulation system increase its overall thermal conductivity by thermal bridging the cells or the fibers of the insulation material. The moisture ingress into pipe insulation threatens the thermal performance and the overall efficiency of the building mechanical system. This phenomenon is also responsible for the mold growth inside occupied spaces and causes the pipelines to be more vulnerable to corrosion. Although a wide range of vapor barriers are used for preventing water vapor penetration into pipe insulation, common experience in the field shows that water vapor will inevitably ingress into the insulation materials from the end joints or from the cracks created during insulation installation. How to account for the moisture ingress on pipe insulation service life and thermal performance is still an open question. Thermal conductivity is one of the most important properties for evaluating the thermal performance of the pipe insulation systems. Using a new test apparatus, the thermal conductivity of pipe insulation systems below ambient temperature and in wet conditions with moisture ingress was measured. Fiberglass and phenolic pipe insulation were tested to investigate the moisture effects on the material thermal conductivity. The data showed that these two types of pipe insulation systems had quite different water absorption rates due to different characteristics of the material and its structure. A serious degradation of fiberglass pipe insulation thermal performance was observed and the thermal conductivity increased by as much as 3 times when the moisture content was about 12 percent in volume. Tested at a different condition, the thermal conductivity of phenolic pipe insulation increased to 1.6 times of the original value and the moisture content was 5% in volume. Considering the gravity effect, the moisture content on the top and bottom C-shells were separately measured and discussed in this paper

Evidence for elevated emissions from high-latitude wetlands contributing to high atmospheric CH4 concentration in the early Holocene

The major increase in atmospheric methane (CH4) concentration during the last glacial-interglacial transition provides a useful example for understanding the interactions and feedbacks among Earth\u27s climate, biosphere carbon cycling, and atmospheric chemistry. However, the causes of CH4 doubling during the last deglaciation are still uncertain and debated. Although the ice-core data consistently suggest a dominant contribution from northern high-latitude wetlands in the early Holocene, identifying the actual sources from the ground-based data has been elusive. Here we present data syntheses and a case study from Alaska to demonstrate the importance of northern wetlands in contributing to high atmospheric CH4concentration in the early Holocene. Our data indicate that new peatland formation as well as peat accumulation in northern high-latitude regions increased more than threefold in the early Holocene in response to climate warming and the availability of new habitat as a result of deglaciation. Furthermore, we show that marshes and wet fens that represent early stages of wetland succession were likely more widespread in the early Holocene. These wetlands are associated with high CH4 emissions due to high primary productivity and the presence of emergent plant species that facilitate CH4 transport to the atmosphere. We argue that early wetland succession and rapid peat accumulation and expansion (not simply initiation) contributed to high CH4 emissions from northern regions, potentially contributing to the sharp rise in atmospheric CH4 at the onset of the Holocene

A fractal-based model for soil water characteristic curve over entire range of water content

Soil water characteristic curve (SWCC) has been an important role in hydraulic engineering, civil engineer and petroleum engineering, etc. Most of SWCC models neglected the film flow in the dry state, so that they cannot accurately describe the SWCC over entire range of water content. In this work, an alternative fractal model is proposed to predict the SWCC over entire range of water content by combining Campbell and Shiozawa model and Tao model. The proposed model can well predict twelve sets of experimental data, and its parameters, including the fractal dimension, the saturated volumetric water content, the matric suction at oven-dry condition, and the air-entry value, accord with theoretical value. The results show that there is a strong linear relationship between volumetric water content and matrix suction in log-log scale for different fractal pore-size distribution of soils. In addition, good agreement is obtained between the experimental data and the model predictions in all of the cases.Cited as: Jin, T., Cai, X., Chen, Y., Jiang, S., Wei, W. A fractal-based model for soil water characteristic curve over entire range of water content. Capillarity, 2019, 2(4): 66-75, doi: 10.26804/capi.2019.04.0

Deletion of Metallothionein Exacerbates Intermittent Hypoxia-Induced Oxidative and Inflammatory Injury in Aorta

The present study was to explore the effect of metallothionein (MT) on intermittent hypoxia (IH) induced aortic pathogenic changes. Markers of oxidative damages, inflammation, and vascular remodeling were observed by immunohistochemical staining after 3 days and 1, 3, and 8 weeks after IH exposures. Endogenous MT was induced after 3 days of IH but was significantly decreased after 8 weeks of IH. Compared with the wild-type mice, MT knock-out mice exhibited earlier and more severe pathogenic changes of oxidative damages, inflammatory responses, and cellular apoptosis, as indicated by the significant accumulation of collagen, increased levels of connective tissue growth factor, transforming growth factor β1, tumor necrosis factor-alpha, vascular cell adhesion molecule 1,3-nitrotyrosine, and 4-hydroxy-2-nonenal in the aorta. These findings suggested that chronic IH may lead to aortic damages characterized by oxidative stress and inflammation, and MT may play a pivotal role in the above pathogenesis process