Humidity Gradient Research Articles

Highly Accelerated Stress Testing of Proton Exchange Fuel Cell Membranes for Heavy Duty Transportation Applications

According to the US DOE’s multi-year Fuel Cell research, development, and demonstration plan, a 30,000 h lifetime, approximately four times that of the light-duty vehicles (LDV), is required for Heavy Duty Vehicle (HDV) applications [1]. Thus, highly accelerated stress tests are necessary in order to assess the viability to novel membrane concepts within a reasonable amount of time. Previously we have reported the development of a highly accelerated stress test (HAST) to generate local stressful conditions that are representative of those in automotive fuel cell stacks [2]. Using a 50-cm2 cell cycled between 0.05 and 1.2 A/cm2 with a low inlet RH in the co-flow configuration, the HAST creates a distribution of combined mechanical/chemical stressors in the membrane with the maximum chemical stress occurring near the gas inlets and the maximum mechanical stress near the outlets. Conducting HASTs using a current distribution measurement tool and a shorting/crossover diagnostic method to track the state of health of a state-of-the-art membrane containing both a mechanical support and a cerium-containing chemical stabilizing additive, the result shows that the membrane location with the most severe thinning coincides with that of the deepest membrane hydration cycling. Upon examination of the cerium redistribution patterns after the test, it was found that the severe humidity cycling generated by the HAST condition near the outlet region not only generated the highest membrane mechanical stress but also resulted in the strongest water flux, which may cause local depletion of the cerium added as chemical stabilizer.In this study, we have focused on determining the root cause of membrane failure in the region of hydration cycling. Two hypotheses were investigated. The first is that chemical degradation can be accelerated in the presence of mechanical stress. The chemical degradation leads to membrane thinning which, in turn, leads to fewer sulfonic acid sites in the membrane available for Ce cation exchange. Two synergistic pathways for membrane degradation by combined mechanical and chemical stressors have been summarized by Kusoglu and Weber [3]. Ex-situ hydrogen peroxide vapor cell tests conducted with a pressure bias across the membrane to create a tensile stress were conducted to see if mechanical stress has an impact on membrane chemical degradation rate [4].The second hypothesis is that local depletion of the mobile Ce stabilizer in regions of high humidity gradients can lead to chemical degradation in those regions. We have shown previously that humidity gradients can cause cations to move with convective forces from wetter to drier regions within a perfluoro-sulfonic acid (PFSA) membrane [5]. To study this hypothesis, we conducted two types of tests. First, we repeated the HAST tests of the state-of-the-art membranes and stopped the tests prior to the onset on membrane thinning to see whether Ce depletion occurs before or after the onset of thinning. We also ran HAST tests on membranes which contained no Ce stabilizer to see if membrane failure still occurred in the region of strongest humidity cycles. In the absence of stabilizer, we expect chemical degradation to occur faster towards the cell inlets where, on average, the MEA is driest.We will show that the HAST test significantly accelerates membrane failure by increasing temperature and frequency of local deep humidity cycles without changing the primary failure mode or location of a state-of-the-art membrane. This work suggests that these HAST tests can be used to accelerate the development of membranes for HD fuel cell applications. DOE H2 Heavy Duty Truck Targets; https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf Y.-H. Lai et. al, J. Electrochem. Soc., 165 (6) (2018) F3100-F3103Kusoglu and Weber, J. Phys. Chem. Lett., 6, 4547 (2015)Y.-H. Lai et. al, ECS s 2021; https://iopscience.iop.org/article/10.1149/MA2021-02381128mtgabs F.D. Coms et. al, ECS s 2021; https://iopscience.iop.org/article/10.1149/MA2021-02381130mtgabs

Cellulose‐Reinforced Programmable and Stretch‐Healable Actuators for Smart Packaging

AbstractBiomimetic actuators are promising candidates for smart soft robotics. The applications of state‐of‐the‐art actuators require the combination of programmable stimuli‐responsiveness, excellent robustness, and efficient self‐healing ability in a wide‐range of working conditions. However, these properties may be mutually exclusive. Inspired by biological tissues, two kinds of polyelectrolytes including polyvinyl alcohol (PVA) and polystyrene sulfonate (PSS) are exploited as the fillers of cellulose nanofibrils (CNFs) for the fabrication of the CNF/PVA/PSS (CAS) film via the assembly of the physically‐crosslinked network through multiple H‐bonding and electrostatic interactions. Achieved by a casting‐evaporation strategy, internal stress is stored within the polymer matrix and transforms into reversible anisotropic bending deformations in response to a humidity gradient. The speed, direction, and pitch of the bending can be programmed by tailoring the internal stresses and geometry of the samples. Moreover, the H‐bonded network also contributes to the effective energy dissipation toward high toughness during tensile stretching, as well as self‐healing ability during moisture saturation of the CAS films. This enables the fabrication of a humidity‐sensitive flower‐shaped actuator and self‐healable packaging paper. This study presents a biomimetic strategy for the fabrication of multi‐functional soft robotics, which holds great promise for applications in the fields of biosensors and smart packaging.

A Climatology of Drylines in the Interior of Subtropical Southern Africa

Abstract A climatology of synoptic drylines on the subtropical southern African interior plateau (SAP) is developed using ERA5 reanalysis specific humidity and surface temperature gradients and an objective detection algorithm. Drylines are found to occur regularly during spring and summer (September–March), and almost daily during December of that period, but rarely in winter. A westward shift in peak dryline frequency takes place through the summer. Drylines peak first over the eastern parts of the SAP during November with a mean of 10 drylines and then over the central (mean of 12) and western SAP (mean of 20) in December. During midsummer, drylines over the eastern SAP are negatively correlated with drylines in the west. Between 1980 and 2020, a significant correlation exists between ENSO and dryline days over the eastern (r = 0.44; p value = 0.004) and central (r = 0.41; p value = 0.008) SAP with fewer drylines (up to 10) occurring during years with increased surface moisture and more drylines (up to 45) occurring during years with decreased surface moisture. Drylines forming over the eastern parts of the SAP were more likely to move westward than drylines over the central and western parts. Onset times across the SAP show that drylines have a tendency to form during either the late morning to early afternoon (1100 and 1400 LST) or during the early evening hours (1700 and 2000 LST), suggesting that the surface heat trough (Kalahari heat low) and westward moisture transport mechanisms, such as the Limpopo low-level jet and ridging highs, are responsible for the formation of most drylines across the SAP. Significance Statement “Drylines” are used to describe boundaries separating regions of very dry air from those with much higher moisture content. The importance of these drylines is that they tend to act as a trigger for thunderstorms, which can produce severe weather. In this study, we build a long-term climatological description of drylines in subtropical southern Africa. We find that drylines are most frequent over eastern South Africa during the early summer, a time when storms with large hail and damaging winds are most likely to occur. Drylines are sensitive to moisture circulation patterns and respond differently during El Niño and La Niña years, with generally more drylines during El Niño over eastern South Africa and fewer during La Niña.

Experimental and numerical investigation on the effect of heat and moisture coupling migration of unsaturated lateritic clay for the soil thermal storage system

The heat released by buried pipes of the soil thermal storage (STS) system will inevitably aggravate the coupling effect of heat and moisture migration in the surrounding soil, which may affect soil thermal properties and thermal storage characteristics. However, there is no conclusive evidence. A series of model tests were conducted to investigate the potential effect of the heat and moisture coupling migration on the heat transfer characteristics of buried pipes. A three-dimensional model considering the temperature dependence of soil thermal conductivity was established and verified. The effects of heat storage temperature and initial soil moisture on the heat transfer characteristics of buried pipes were further evaluated using the proposed model. Test results show that the thermal conductivity of lateritic clay increases with increasing soil temperature due to the latent heat transfer of vapor. For lateritic clay with an initial saturation of 13.42 %, the thermal conductivity increases to 7.3 times that of 5 °C at 90 °C. The driving force of moisture migration is generated from both temperature and humidity gradient. Soil moisture near to the buried pipe varies significantly during the first 3 ∼ 12 h due to the hysteresis of moisture migration caused by the temperature gradient driving. The soil moisture variations on the one-dimensional conditions are more significant than those under three-dimensional conditions due to the effects of gravity and paths on the moisture migration. Model validation results show that ignoring the moisture migration and temperature dependence of soil thermal conductivity will lead to the lower prediction value of the numerical model. Simulation results show that the influence of the initial soil moisture on the heat and moisture coupling migration should be taken into account when accurately evaluating the performance of STS system.

An experimental study on the influence of continuous ambient humidity conditions on relative humidity changes, chloride diffusion and microstructure in concrete

Most engineering structures are exposed to various harsh environments, such as temperature fluctuations and humidity cycles, simultaneously. Additionally, moisture transfer and corrosive ion transport in concrete are driven by humidity gradients. Therefore, studying Chloride transport in concrete under constant humidity conditions is a meaningful research project. In this work, a new experimental setup was designed, and the Chloride diffusion behavior of concrete under a continuous humidity environment and NaCl immersion was investigated. Meanwhile, to accurately evaluate the internal humidity of concrete, humidity sensors were applied to the concrete. Additionally, the impacts of the water-binder ratio (w/b) and ambient humidity on the humidity diffusion coefficient, free Chloride content and bound Chloride content in concrete were evaluated. The microstructure was characterized by scanning electron microscopy, X-ray diffraction and mercury intrusion porosimetry. The results show that the content of free Chloride increases with an increasing w/b ratio. The humidity diffusion coefficient of concrete during water absorption (continuous high humidity environment) is significantly higher than that during water loss (continuous dry environment). Furthermore, under the drying condition, the Chloride content and the humidity diffusion coefficient on the concrete surface gradually increased, while during the wetting procedure, the Chloride content inside the concrete increased, and the humidity diffusion coefficient gradually decreased. However, the bound Chloride content inside the concrete is not affected by the humidity level in the environment. In the wetting environment, the calcium hydroxide in the matrix is gradually consumed, and the Chloride diffuses to the matrix to form more Friedel's salt and calcium carbonate. Moreover, lowering the w/b ratio or increasing the ambient humidity can enhance the formation of more hydrated compounds (C–S–H gel), which can reduce the total porosity and can also improve the ability of concrete to resist Chloride diffusion. Overall, this study provides a better understanding of and insight into the design and maintenance of seaside RC infrastructures.

Nacre-inspired composite film with mechanical robustness for highly efficient actuator powered by humidity gradients

Exploring and fabricating smart actuating materials that strike the perfect balance between humidity response and mechanical integrity (especially wet tensile strength) via reasonable structural design and simple yet low-cost preparation is critical for biomimetic devices, soft robotics, artificial muscles and generators, but it remains challenging. Herein, inspired by the structure of natural nacre, we demonstrated a robust yet highly sensitive composite film-based humidity actuator composed of carboxymethyl cellulose (CMC), MXene nanosheets, and multivalent aluminum ions (Al3+) via a facile evaporation-induced self-assembly method. The synergistic reinforcing effects of MXene nanosheets and Al3+ through hydrogen and ionic bonding as well as the densely hierarchical microstructure endow the composite film with both an ultrahigh mechanical strength (273.6 MPa), a desirable toughness (7.95 MJ/m3) and even an impressive wet tensile strength (154.2 MPa) at 97 % humidity. Interestingly, the unique laminated structure and water-induced swelling effect of CMC and MXene synergistically enable the composite film with large shape deformation, sensitive actuation (less than 2.3 s) and exceptional cycling stability (over 1500 cycles) upon exposure to humidity gradients. Based on the above merits, the composite film actuator can be well constructed to simulate a flying dragonfly, human finger, artificial muscle, and has also been preliminarily employed as a moist-electric generator, which provides new insight for designing comprehensive composite film-based actuators and reveals their extensive applications.

Humidity gradients in the air spaces of leaves.

Stomata are orifices that connect the drier atmosphere with the interconnected network of more humid air spaces that surround the cells within a leaf. Accurate values of the humidities inside the substomatal cavity, wi, and in the air, wa, are needed to estimate stomatal conductance and the CO2 concentration in the internal air spaces of leaves. Both are vital factors in the understanding of plant physiology and climate, ecological and crop systems. However, there is no easy way to measure wi directly. Out of necessity, wi has been taken as the saturation water vapour concentration at leaf temperature, wsat, and applied to the whole leaf intercellular air spaces. We explored the occurrence of unsaturation by examining gas exchange of leaves exposed to various magnitudes of wsat - wa, or Δw, using a double-sided, clamp-on chamber, and estimated degrees of unsaturation from the gradient of CO2 across the leaf that was required to sustain the rate of CO2 assimilation through the upper surface. The relative humidity in the substomatal cavities dropped to about 97% under mild Δw and as dry as around 80% when Δw was large. Measurements of the diffusion of noble gases across the leaf indicated that there were still regions of near 100% humidity distal from the stomatal pores. We suggest that as Δw increases, the saturation edge retreats into the intercellular air spaces, accompanied by the progressive closure of mesophyll aquaporins to maintain the cytosolic water potential.

Development of low-cost RFID sensors dedicated to air pollution monitoring for preventive conservation

Monitoring of atmospheric pollutants is a key point for preventive conservation since these species are known to impact the integrity of many artifacts including metals, papers, pigment and textiles. The problem can be amplified in closed environments, like in exhibition rooms and showcases, where temperature and relative humidity gradients and levels can introduce additional micro-climatic problems. One objective of the EU-SensMat project concerns the development of low cost and low visual nuisance sensors sensitive to these pollutants, making them affordable for all museums including small ones. For this purpose, the Radio-Frequency Identification (RFID) technology was considered to produce air-quality sensors based on reactive metallic dosimeter. Besides the low cost, they can be easily integrated to other existing RFID applications such as identification tasks since the interrogation is made with a commercial UHF-RFID reader. The description and the main features of these sensors are discussed in this paper. Moreover, as it will be shown, the subsequent chemical analysis of the sensitive part of the sensors provide useful information to determine the origin of the pollutants.

Surface atmospheric duct over Svalbard, Arctic, related to atmospheric and ocean conditions in winter

ABSTRACT Atmospheric ducts could disturb radar detection and radio communication in the Arctic and risk increasing human activities under Arctic warming. It is an urgent need to understand atmospheric ducts in the Arctic, with distinct atmospheric systems and environment. This study attempts to analyze the surface atmospheric ducts over Svalbard, as a critical region in the Arctic Ocean, and discuss the relation to atmospheric and oceanic conditions, based on observation and reanalysis data. The results show an occurrence of 12.6 percent, mean strength of 1.30 MU, and mean depth of 13 m for the surface duct in Svalbard winter from December 2018 to February 2020. The surface duct is characterized as two types: T-type ducts mainly constructed by temperature inversion and H-type ducts constructed by a humidity gradient. The T-type duct dominates the surface duct in Svalbard winter, with an appearance percentage of 80 percent, indicating an importance of temperature inversion in surface duct construction. The surface duct is closely related to atmospheric and oceanic conditions in Svalbard winter, because the T-type duct occurs in colder, drier, and northeasterly weather and the H-type duct occurs in warmer, wetter, and southeasterly weather with higher sea surface temperature.

Role of ventilation and cleaning for controlling house dust mite allergen infestation: A study on associations of house dust mite allergen concentrations with home environment and life styles in Tianjin area, China.

House dust mites produce well-known allergens for asthma and allergy among children. To study house dust mite allergen exposure level in northeast China and characterize its association with indoor environmental factors and cleaning habits, we inspected 399 homes in Tianjin area and collected dust from mattresses. Dermatophagoides farinae (Der f) and Dermatophagoides pteronyssinus (Der p) were detected by the enzyme-linked immunosorbent assay (ELISA) method. The medians of total allergen concentrations for spring, summer, autumn, and winter were 524 ng/g, 351 ng/g, 1022 ng/g, and 1010 ng/g. High indoor air relative humidity (RH), low air change rate, indoor dampness, and frequent changing of quilt cover/bedsheet/pillow case were significantly associated with high house dust mite allergen concentration (relative risk [RR]: RH, 1.18-1.34; air change rate, 0.97-1.00; dampness, 2.92-3.83; changing quilt cover/bedsheet/pillow case, 0.66-0.75). The decrease in the absolute humidity gradient between indoors and outdoors that occurs with increased air change rate may explain why a high ventilation reduces house dust mite allergen concentration. The findings of this study show the importance of ventilation and cleaning for controlling house dust mite allergens. We found that the decrease in additional absolute humidity (e.g., humidity indoor -humidity outdoor ) with increased air change rate may be the main reason that a high ventilation rate reduces house dust mite allergen concentration. Ventilation and cleaning should be both considered for creating a healthy home environment.

Study of internal moisture condensation for the conservation of stone cultural heritage

The natural moisture condensation is considered an important decay factor for stone relics. If protection is only concerned with the conditions under which water forms on the surface, it can cause liquid water to form inside the stone relics over and over again. In this situation, it can lead to considerable damage to the stone relics in fact. In order to investigate the condensed water inside the stone relics, critical conditions have been calculated and a verification experiment has been conducted. The process of the moisture from a gaseous to a liquid state has been studied by several ways, such as the temperature and relative humidity analysis, the resistance and moisture analysis. The situation of both fresh and weathered sandstone samples is considered and analyzed. The results show that the liquid water was produced inside the stone relics before it was formed on the surface when the temperature and humidity gradient distribution from the rock surface to the inner rock is reduced. At last, this paper provides useful guidance to eliminate the harmful effects of the condensed water.

Lidar-Derived Aerosol Properties from Ny-Ålesund, Svalbard during the MOSAiC Spring 2020

In this work, we present Raman lidar data (from a Nd:YAG operating at 355 nm, 532 nm and 1064 nm) from the international research village Ny-Ålesund for the time period of January to April 2020 during the Arctic haze season of the MOSAiC winter. We present values of the aerosol backscatter, the lidar ratio and the backscatter Ångström exponent, though the latter depends on wavelength. The aerosol polarization was generally below 2%, indicating mostly spherical particles. We observed that events with high backscatter and high lidar ratio did not coincide. In fact, the highest lidar ratios (LR > 75 sr at 532 nm) were already found by January and may have been caused by hygroscopic growth, rather than by advection of more continental aerosol. Further, we performed an inversion of the lidar data to retrieve a refractive index and a size distribution of the aerosol. Our results suggest that in the free troposphere (above ≈2500 m) the aerosol size distribution is quite constant in time, with dominance of small particles with a modal radius well below 100 nm. On the contrary, below ≈2000 m in altitude, we frequently found gradients in aerosol backscatter and even size distribution, sometimes in accordance with gradients of wind speed, humidity or elevated temperature inversions, as if the aerosol was strongly modified by vertical displacement in what we call the “mechanical boundary layer”. Finally, we present an indication that additional meteorological soundings during MOSAiC campaign did not necessarily improve the fidelity of air backtrajectories.

Probing water uptake gradient in an epoxy matrix via scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) is used to detect and observe the presence of water inside polymeric film at the microscopic scale around 200–500 μm. The principle is based on the use of SECM performed with a room temperature ionic liquid (RTIL) and K4Fe(CN)6 as redox sensor. The particular electrochemical behaviors obtained in such medium have been investigated by performing cyclic voltammetry and approach curves in negative feedback mode. Then, the cross-section of epoxy resin films has been repeatedly scanned using the SECM probe over several days of immersion in the RTIL. As the presence of water impacts the electrolyte viscosity, the electrochemical signal was sensitive to the amount of water around the microelectrode. The sensitivity of this technique to the presence of water released from the materials at the microscopic scale was demonstrated by comparing electrochemical signals obtained on dry and saturated specimens. Such results appeared to be very promising for the development of new methods to locally detect the presence of water in thick polymeric materials and to measure humidity gradient within the material thickness.

Fabrication of the Fabry–Pérot cavity with acrylate AB glue film via dual pressure assistance for humidity sensing

A method for fabricating a thin film Fabry–Pérot (F–P) cavity via dual pressure-assisted acrylate AB glue was studied. The method pressurizes both the acrylate AB glue to generate bubbles and the subsequent inflated film to make it thinner and more sensitive. The F–P cavity was fabricated by attaching the ultrathin film to a glass tube end face and a single-mode fiber in the glass tube to form a two-beam interference model. On the basis of two cycles and several repeated experiments for the humidity gradient, the linear and stable characteristics, and the humidity sensitivity of the F–P cavity with a thin film was demonstrated. The humidity sensitivity was 80.68 pm/% RH and 82.17 pm/% RH under two rising humidity experiments. Acting as the humidity sensing material for the first time, the acrylate AB glue film of the F–P cavity shows good stability and repeatability. In addition, the dual pressure-assisted method introduces a way to produce fiber-optic sensors with ultrathin film.

Opposing industrial era moisture patterns between basins and mountains in southern arid Central Asia

Investigations of the evolution of naturally and anthropogenically driven hydrology in arid regions are of great significance for hydrological forecasts. Here, we built the past ∼500-year history of lake area and discharge of Lake Tuosu in the northeastern Qaidam Basin. We found that the lake area and inflow variations were sensitive to westerly-forced winter-spring precipitation and showed long-term decreasing trends after 1850. Enhanced local human activities (e.g., agricultural irrigation) led to further rapid shrinkage of Lake Tuosu during 1990–2000, and the lake size reached its minimum in the past 500 years in approximately 2000. Our integrated moisture indices for mountains and basins in southern arid Central Asia showed opposing trends, and the humidity gradient from mountains to basins successively increased after 1850, which may be linked to the migration of the boreal westerlies, global warming, and human activities. After 1950, the humidity increased further, reaching its maximum value in approximately 2000, which likely resulted from the excessive utilization of water resources from anthropogenic activities. Therefore, the mountain-river-basin hydrological system in arid Central Asia has changed significantly, beyond the natural variation pattern, after CE 1950. Therefore, integrated management and rational utilization of water resources are important for ecological protection and sustainable development in the future.

Macro- and Microresearch on Swelling Characteristics and Deformation Mechanism of Red-Bed Mudstone in Central Sichuan, China

Exploring the development of multiscale behaviors of red-bed mudstone is beneficial for in-depth evaluation of swelling capacity and its progressive failure mechanism. In this paper, a macro-micro study was performed on rock samples in central Sichuan, China. The influence of environmental factors such as water content, degree of soaking, and gaseous moisture absorption was discussed. Spatial characterizations were finally described from pore structure and distribution. Experimental results suggested that deformation curve under water immersion had three stages of rapid growth, deceleration growth, and gradual stabilization. It can enter stable deformation within 60~80h and has short-term swelling effects, while gaseous moisture absorption presented long-term performance during 0~700 h. The difference in deformation between partial and complete immersion may be the release of swelling potential caused by humidity gradient and capillary suction. The strain-time curves during water immersion all tended to short-term swelling. Moreover, repeated drying and wetting promoted the time of shrinkage adjustment in the second cycle to be significantly shortened, resulting in a large amount of irreversible plastic deformation. Although initial water content influenced the final stable strain, it only changed the degree of deformation at initial stage. For the microscale structures, the closer to the end, the greater the porosity and the smaller the middle. The average porosity after 0, 1, and 2 dry and wet cycles reached 0.227%, 4.027%, and 6.121%, respectively. Geometric parameters such as volume and surface area of the pores enlarged with the increase of the number of cycles. Small pores gradually evolved into microcracks and large fissures. Besides, the pores developed from “tree-like” to “net-like” structures with continuous cycles.

Need for split: integrative taxonomy reveals unnoticed diversity in the subaquatic species of Pseudohygrohypnum (Pylaisiaceae, Bryophyta).

We present an integrative molecular and morphological study of subaquatic representatives of the genus Pseudohygrohypnum (Pylaisiaceae, Bryophyta), supplemented by distribution modelling of the revealed phylogenetic lineages. Phylogenetic analyses of nuclear and plastid datasets combined with the assemble species by automatic partitioning (ASAP) algorithm revealed eight distinct species within the traditionally circumscribed P. eugyrium and P. subeugyrium. These species are therefore yet another example of seemingly widely distributed taxa that harbour molecularly well-differentiated lineages with narrower distribution ranges. Studied accessions that were previously assigned to P. eugyrium form three clearly allopatric lineages, associated with temperate regions of Europe, eastern North America and eastern Asia. Remarkably, accessions falling under the current morphological concept of P. subeugyrium were shown to be even more diverse, containing five phylogenetic lineages. Three of these lineages occur under harsh Asian continental climates from cool-temperate to Arctic regions, while the remaining two, referred to P. subeugyrium s.str. and P. purpurascens, have more oceanic North Atlantic and East Asian distributions. Niche identity and similarity tests suggested no similarity in the distributions of the phylogenetically related lineages but revealed the identity of two East Asian species and the similarity of two pairs of unrelated species. A morphological survey confirmed the distinctness of all eight phylogenetic lineages, requiring the description of five new species. Pseudohygrohypnum appalachianum and P. orientale are described for North American and East Asian plants of P. eugyrium s.l., while P. sibiricum, P. subarcticum and P. neglectum are described for the three continental, predominantly Asian lineages of P. subeugyrium s.l. Our results highlight the importance of nontropical Asia as a center of bryophyte diversity. Phylogenic dating suggests that the diversification of subaquatic Pseudohygrohypnum lineages appeared in late Miocene, while mesophilous species of the genus split before Miocene cooling, in climatic conditions close to those where the ancestor of Pseudohygrohypnum appeared. We speculate that radiation of the P. subeugyrium complex in temperate Asia might have been driven by progressive cooling, aridification, and increases in seasonality, temperature and humidity gradients. Our results parallel those of several integrative taxonomic studies of North Asian mosses, which have resulted in a number of newly revealed species. These include various endemics from continental areas of Asia suggesting that the so-called Rapoport’s rule of low diversity and wide distribution range in subpolar regions might not be applicable to bryophytes. Rather, the strong climatic oscillations in these regions may have served as a driving force of speciation and niche divergence.

Water Manipulation through Curvature Energy on Humidity Microparticles

The electric field created in a curvature energy sensor on air microparticles is used to obtain a temperature-humidity map by stereoradially of the sensor design to detect and measure the temperature and humidity of certain local region of the environment space. Likewise,considering the curvature energy as the deviation of any field interaction,even the obstruction to its proper flow, is designed and created a humidityresistor sensor to the control and optimization of humidity in a space with different gradients of humidity, pressure and temperature in a radial detection and measuring. Then the sensing problem is a problem of free boundary conditions where is satisfied an energy functional of norm ,to curvature functions that satisfy in the temperature and humidity function the change limit condition This carries to that the temperature-humidity sensor must be designed on a length gauge to measure the changes of humidity and temperature in the space.

Hydrology and thermal regime of an ice‐contact proglacial lake: Implications for stream temperature and lake evaporation

AbstractThe formation of lakes as glaciers retreat can potentially influence stream temperature and enhance catchment water losses via evaporation. This study quantified the summer water and energy budgets and thermal regime of an ice‐contact proglacial lake below Bridge Glacier, British Columbia, to link ongoing glacier retreat with downstream effects. The ice‐proximal and distal portions of the lake behave differently due to a mid‐lake recessional moraine, against which icebergs are pinned by the dominant katabatic wind. Iceberg cover of the ice‐proximal basin ranged from 16% to 75%. Temperature profiles in the ice‐proximal basin were dominantly near‐isothermal at 1 to 1.4°C, with the exception of diurnal warming of the top 1 m of water and the presence of a colder layer near the lake bed at some sites, presumably caused by subglacial discharge of turbid water. Subaqueous iceberg melt limited warming by consuming heat from the water column. The distal basin exhibited varying degrees of thermal stratification, with turbidity inferred to have a greater influence on water density than temperature. Most of the warming between lake inflow and outflow occurred in the distal basin, where net radiation was the dominant surface energy input and net lateral advection the dominant energy sink. As a result of the suppressed water temperature, humidity gradients over the lake favoured condensation, not evaporation. Estimates of iceberg melt volume for 2013 exceeded glacier discharge into the lake. Therefore, when the glacier eventually becomes land‐terminating, icebergs are expected to disappear within a year, resulting in higher water temperatures both in the lake and downstream. Higher lake temperatures could also cause an eventual shift from condensation to evaporation, which would tend to reduce catchment water yield over and above reductions associated with loss of glacier area.

Dynamic and Thermal Effects of the Tibetan and Iranian Plateaus on the Northward-Propagating Intraseasonal Oscillation during Boreal Summer

Abstract This study investigates the dynamic and thermal effects of the Tibetan and Iranian Plateaus (TIP) on the characteristics of the northward-propagating boreal summer intraseasonal oscillation (BSISO) and reveals associated physical mechanisms. The relative importance of the Tibetan Plateau (TP) and Iranian Plateau (IP) to the northward propagation of BSISO is also detected. The findings are based on comparative analyses of the control run and six sensitivity experiments using the atmospheric model component of CAS FGOALS-f3-L (the low-resolution version of the Chinese Academy of Sciences Flexible Global Ocean–Atmosphere–Land System model, finite-volume version 3). It is demonstrated that the absence of TIP surface sensible heat or terrain restricts the occurrence of upper-level easterly and lower-level westerly anomalies, as well as moisture convergence over the Asian summer monsoon (ASM) region, which leads to a weakened easterly vertical wind shear with a narrowed range and the generation of a negative meridional specific humidity gradient in the northern Bay of Bengal. These mean-state changes are not conducive to the formation of positive barotropic vorticity together with planetary boundary layer moisture convergence to the north of the convective center, thus impeding the northward propagation of the BSISO. Results indicate that the combined TIP area, via its dynamic and thermal effects, modulates the northward-propagating BSISO by directly affecting the vertical wind shear and meridional moisture gradient in the northern Indian Ocean. By contrast, the TP plays a decisive role in the BSISO northward propagation due to the limited dynamic and thermal effects of IP on the background circulation and water vapor convergence over the ASM region.