Rate Of Decrease In Density Research Articles

Proton conductivity and durability of Ce-based hybrid proton exchange membranes synchronously enhanced by dual-function γ-AlOOH@Ti-supported CeO2 composite oxide

To enhance the proton conductivity and durability of Ce-based hybrid proton exchange membranes (PEMs), this study fabricates modified perfluorosulfonic acid (PFSA) hybrid membranes by incorporating the dual-function γ-AlOOH@Ti-supported CeO2 composite oxide (γ-AlOOH@Ti/CeO2). In addition to combining the inherent proton conductivity of γ-AlOOH with the excellent radical scavenging ability of CeO2, both the proton conductivity and durability of Ce-based PEMs are further improved by introducing Ti-dopant, which not only increases hydrogen vacancies on the surface of γ-AlOOH, which facilitate proton conduction, and induces electron transfer from γ-AlOOH@Ti to CeO2, which enhance free radical adsorption. As results shown, the proton conductivity and the fluoride release value of the resulting hybrid membrane are about 76 % higher and 35.25 % lower than those of the PFSA-CeO2 membrane, respectively. Moreover, the performance of cells shows that, after accelerated degradation testing, the PFSA-γ-AlOOH@Ti/CeO2 membrane exhibits the lowest peak power density decrease rate, the impedance increase rate and hydrogen crossover current density, with 11.79 %, 27.54 % and 3.04 mA cm−2, respectively. These results suggest that compared to CeO2-hybrid PEMs, γ-AlOOH@Ti/CeO2-based hybrid PEMs exhibit higher proton conductivity and superior chemical stability, indicating the potential application of γ-AlOOH@Ti/CeO2-based hybrid PEMs in proton exchange membrane fuel cells.

Quantitative Optimization of Handheld Probe External Pressure on Dermatological Microvasculature Using Optical Coherence Tomography-Based Angiography.

Optical Coherence Tomography (OCT)-based angiography (OCTA) is a high-resolution, high-speed, and non-invasive imaging method that can provide vascular mapping of subcutaneous tissue up to approximately 2 mm. In dermatology applications of OCTA, handheld probes are always designed with a piece of transparent but solid contact window placed at the end of the probe to directly contact the skin for achieving better focusing between the light source and the tissue, reducing noise caused by minor movements. The pressure between the contact window and the skin is usually uncontrollable, and high external pressure affects the quality of microvascular imaging by compressing the vessels and obstructing the underlying blood flow. Therefore, it is necessary to determine a pressure range to ensure that the vessels can be fully imaged in high-quality images. In this paper, two pressure sensors were added to the existing handheld OCT probe, and the imaging probe was fixed to a metal stand and adjusted vertically to change the pressure between the probe and the tested skin site, a gradient of roughly 4 kPa (with 1-2 kPa error) increase was applied in each experiment, and the impact of pressure to the vessel was calculated. The experiment involved a total of five subjects, three areas of which were scanned (palm, back of the hand, and forearm). The vessel density was calculated to evaluate the impact of external pressure on angiography. In addition, PSNR was calculated to ensure that the quality of different tests was at a similar level. The angiography showed the highest density (about 10%) when the pressure between the contact window on the probe and the test area was between 3 and 5 kPa. As the pressure increased, the vascular density decreased, and the rate of decrease varied in different test areas. After fitting all the data points according to the different sites, the slope of the fitted line, i.e., the rate of decrease in density per unit value of pressure, was found to be 4.05% at the palm site, 6.93% at the back of the hand, and 4.55% at the forearm site. This experiment demonstrates that the pressure between the skin and contact window is a significant parameter that cannot be ignored. It is recommended that in future OCTA data collection processes and probe designs, the impact of pressure on the experiment be considered.

Electronic Structure Effect of PtCo Alloy with Adjustable Compositions for Efficient Methanol Electrooxidation.

Various efficient strategies have been developed to overcome the anodic electrocatalyst issue of methanol-based fuel cells owing to their complicated methanol electrooxidation mechanism. In this work, PtCo nanoparticles with adjustable compositions supported on multiwalled carbon nanotubes (Pt1Cox/MWCNTs) through the adsorbing-coating-annealing-etching route were synthesized. Compared with the Pt/C catalyst, Pt1Co3/MWCNTs exhibit better electrocatalytic MOR activity in both activity and durability. Notably, the electrochemical mass and specific activity of the as-prepared catalyst are 1.04 mA μg-1Pt and 2.18 mA cm-2, respectively, which are higher than those of the Pt/C catalyst. Moreover, the as-prepared sample revealed lower onset potential during the CO stripping test. Furthermore, the Pt1Co3/MWCNTs possess a lower current density decrease rate in chronoamperometry and cyclic durability tests. The enhancement of activity and stability of Pt1Co3/MWCNTs could be ascribed to their ordered morphological structure, the electronic interaction between MWCNTs and PtCo nanoparticles, and the suitable electronic structure effect between Pt/Co ratios. The concept of the catalyst design in this study offers a different guideline for constructing the novel methanol electrooxidation catalyst, which will accelerate the widespread fuel cell practical application.

Dynamic Mechanical Properties and Energy Dissipation Analysis of Sandstone after High Temperature Cycling

In order to study the effect of high temperature cycling on the physical and mechanical properties of rock materials, a box-type resistance furnace was used to conduct high temperature cycling at 400°C 10 times on sandstone specimens in coal mine, and the impact compression tests under 8 loading rates were carried out using a split Hopkinson bar (SHPB) device. Results showed that, with the increase of cycle times, the gray white sandstone specimen gradually showed reddish brown spots, and the volume of specimen increased, while the mass, density, and longitudinal wave velocity decreased; in addition, the volume increase rate, the mass decrease rate, the density decrease rate, and the longitudinal wave velocity decreased rate with cycle times showed quadratic function relationship. The dynamic compressive stress-strain curve of sandstone specimens subjected to high temperature cyclic action under impact load was obviously different from that under normal temperature. The dynamic elastic modulus was obviously larger than that under static load. The failure mode of dynamic and static specimens showed brittleness and ductility characteristics, respectively. In the SHPB test, the impact pressure, reflected energy, transmitted energy, and absorbed energy of the rock specimen all increased linearly with the increase of incident energy. The dynamic compressive strength, elastic modulus, and strain rate of sandstone specimens were positively correlated with the incident energy, while the dynamic strain showed negative correlation.

A two-component dynamic stand model of natural thinning

Our investigation aims (1) to derive a dynamic model for mean volume and biomass growth projection over time, considering the competition-induced tree mortality (dynamic size-density model), (2) to design a compatible two-component modelling system composed of the dynamic size-density model and an appropriate density decrease function, and (3) to examine the applicability of this composite natural thinning model to describe the growth dynamics of even-aged coniferous and broadleaved stands.The stand growth projection system was formulated to include three dynamic equations: a density decrease model expressing the reduction in tree number with dominant height growth, and two dynamic size-density models, for mean stem volume and tree biomass respectively. Two size-density formulations (M1 and M2) were derived, each including one local (site- or stand-specific) and three global (common to all stands of the species) parameters. Model M1 suggests a polymorphic set of size-density curves, while model M2 describes size-density curves with variable asymptotes. The goodness-of-fit statistics showed that for radiata pine (Pinus radiata D. Don) and Scots pine (Pinussylvestris L.) datasets the three-model-system based on M1 performed better than the one based on M2. The growth trajectories of downy birch (Betula pubescens Ehrh.) and English oak (Quercus robur L.) stands were described only by model M2. The systems of projection equations explained more than 95% of the variation in most cases.The two-component modelling system is implicitly defined by the stand density and mean tree size (biomass and/or volume) values for a given dominant stand height and set of global model parameters; it does not require any additional stand variables, constants of contested universality or standard-base variable values. It uses stand dominant height as a proxy for time, and inclusion of this growth stage indicator enables the bidirectional dependence between stand density and tree size to be reflected. The composite natural thinning model estimates sets of polymorphic curves with multiple asymptotes. Together with the stand-specific rate of density decrease, this also yields the stand-specific rate of size increase over time and the reduction in tree number, thus enabling prediction of contrasting individual growth patterns of stands of similar initial densities. It accounts for the isometric relationship between plant volume and biomass and can be considered for incorporation as a principal component of a dynamic Stand Density Management Diagram.

Effects of self-irradiation in plutonium alloys

In this paper, we present updated results of self-irradiation effects on 238Pu-enriched 239Pu alloys measured by immersion density, dilatometry, and tensile tests. We obtained the self-irradiation equivalent time of nearly 200 years, nearly 100 years longer than in our previous papers. At this extended aging, we find the rate of decrease in density has slowed significantly, stabilizing around 15.73 g/cc, without signs of void swelling. The volume expansion measured at 35 °C also shows apparent saturation at less than 0.25%. Quasi-static tensile measurement still show gradual increase in the strength of plutonium alloys with age.

Spontaneous large-scale autolysis in Clostridium acetobutylicum contributes to generation of more spores.

Autolysis is a widespread phenomenon in bacteria. In batch fermentation of Clostridium acetobutylicum ATCC 824, there is a spontaneous large-scale autolysis phenomenon with significant decrease of cell density immediately after exponential phase. To unravel the role of autolysis, an autolysin-coding gene, CA_C0554, was disrupted by using ClosTron system to obtain the mutant C. acetobutylicum lyc::int(72). The lower final cell density and faster cell density decrease rate of C. acetobutylicum ATCC 824 than those of C. acetobutylicum lyc::int(72) indicates that CA_C0554 was an important but not the sole autolysin-coding gene responding for the large-scale autolysis. Similar glucose utilization and solvents production but obvious lower cell density of C. acetobutylicum ATCC 824 comparing to C. acetobutylicum lyc::int(72) suggests that lysed C. acetobutylicum ATCC 824 cells were metabolic inactive. On the contrary, the spore density of C. acetobutylicum ATCC 824 is 26.1% higher than that of C. acetobutylicum lyc::int(72) in the final culture broth of batch fermentation. We speculated that spontaneous autolysis of metabolic-inactive cells provided nutrients for the sporulating cells. The present study suggests that one important biological role of spontaneous large-scale autolysis in C. acetobutylicum ATCC 824 batch fermentation is contributing to generation of more spores during sporulation.

Age-related changes of markers of bone formation and the relationship with bone mineral density decreasing rates in women

Objective To investigate the relationship between bone formation markers,including bonespecific alkaline phosphatase (BAP),osteocalcin,total alkaline phosphatase (TALP),and bone mineral density decreasing rate(BDR).Methods A cross-sectional study was made in 891 healthy adult women with ages ranging from 20 to 80 years old.Bone mineral density and BDR at posteroanterior spine,the left hip and the left forearm were measured.Levels of serum BAP,osteocalcin,and TALP were detected.The relationship between above bone formation markers and BDR was analysed.Results BDR at various skeletal sites had significant negative correlation with bone formation markers,especially for osteocalcin(r=-0.439 and-0.519,both P＜0.01).After adjustment of age and body mass index,serum BAP,osteocalcin,and TALP,it still exhibited significant correlations with BDR.Stepwise multiple linear regression analysis showed that,bone formation markers were negative determinant factors of BDR,in which,serum osteocalcin was the most significant negative determinant of BDR,between 19.2％ to 26.7％ of the changes in BDR were determined by serum osteocalcin; 9.0％ and 0.8％ of the changes in BDR in spine and forearm,respectively,were determined by serum BAP,whereas its determining effect on femoral neck and total hip was excluded ; only 0.6％ to 5.0％ of the changes in BDR were determined by serum TALP.Conclusion The study indicates the correlation between bone formation markers and bone mineral density decreaseing in women and suggests that,serum osteocalcin is the key determining factor of bone mineral density decreasing,the increase of which may be related with osteoporosis risk. Key words: Marker of bone formation; Bone-specific alkaline phosphatase; Osteocalcin; Total alkaline phosphatase; Bone mineral density decrease rate

What women want - quantifying the perception of hair amount: an analysis of hair diameter and density changes with age in caucasian women

It has long been known that women lose satisfaction with their hair with ageing. Our data show that caucasian women perceive a decrease in hair amount in their mid 40s with a further decrease in the mid to late 50s, which leads to this dissatisfaction. Neither loss of density (hairs per cm(2) ) nor shaft diameter alone can fully account for this perception. A new metric, 'hair amount', is proposed as a quantitative metric combining the impact of both density and diameter on the perception of hair loss. Creation of a single parameter combining the contribution of diameter and density to perception of female age-related hair loss. In total, 1099 caucasian women (ages 18-66 years) with self-perceived hair loss and 315 caucasian women (ages 17-86 years) with no complaint of hair loss were evaluated. Scalp hair diameter was measured using optical fibre diameter and image analysis. Scalp hair density was measured by phototrichogram with manual or automated counting. Parietal scalp hair diameter increased from ages 20 to 40-45 years, then decreased. Hair density was highest in the youngest group, age 20-30 years, and decreased thereafter with increasing rate. In women self-perceiving hair loss, the rate of decrease in density was significantly faster than for women with no self-perception of hair loss. The combined metric 'hair amount' was relatively constant at younger ages, increasing very slightly to age 35 years, then decreasing significantly. Increasing hair shaft diameter offsets decreasing hair density through the mid 30s. After that, a lower rate of diameter increase combined with the decrease in density begins to significantly impact the perception of hair amount so that thinning becomes increasingly more noticeable in the mid 40s to the mid to late 50s. Quantitative determination of hair amount is a useful tool to combine the contributions of hair density and diameter to women's perception of age-related hair loss.

Effects of functional electrical stimulation cycling exercise on bone mineral density loss in the early stages of spinal cord injury

To determine whether bone mineral density loss after spinal cord injury can be attenuated by an early intervention with functional electrical stimulation cycling exercises (FESCE) and to ascertain whether the effect persists after FESCE is discontinued. A prospective study. Twenty-four individuals with spinal cord injury, 26-52 days after spinal cord injury, were divided into FESCE or control groups. FESCE was applied in the initial 3 months and then suspended in the subsequent 3 months. Bone mineral density in the femoral neck and distal femur was measured using dual energy X-ray absorptiometry before training, immediately after the initial 3 months of training, and at the end of the subsequent 3 months. The bone mineral density decrease rate in the distal femur in the FESCE group was significantly less than that in the control group during the initial 3 months. However, there was no significant difference in the subsequent 3 months. FESCE in the early stages of spinal cord injury can partly attenuate bone mineral density loss in the distal femur. However, bone mineral density loss in the distal femur cannot be ameliorated completely by FESCE. In addition, the effect on the attenuation of bone loss in the distal femur faded once FESCE was discontinued.

Baroclinic wave drag from two closely spaced sills in a narrow fjord as inferred from basin water mixing

The dynamics of the entrance to the Ringdalsfjord‐Idefjord at the Swedish‐Norwegian border is described for the first time. A 1‐month‐long high‐resolved data set shows that the mixing rate is extremely high in the basin water between the two sills at Bjällvarpet and Svinesund and that the accompanying horizontal mean buoyancy flux is about 25 mW m−2. During two periods in the observations, the density decrease rate, dρ/dt, below 17 m depth was estimated to be −0.90 and −1.20 kg m−3 d−1, respectively. Our observations support the idea that the tide is subjected to baroclinic wave drag due to generation of internal tides at sills when a densimetric Froude number, based on tidal speed and basin stratification, is subcritical. For supercritical values of the Froude number, basin stratification becomes unimportant, and the tide is subjected to large‐scale topographic drag with jets developing on the lee side of the sills. The total energy loss due to baroclinic wave drag and large‐scale topographic drag during the two periods are 268 and 198 kW, respectively. All power supplied to the internal tides and 1/6 of the power supplied to the jets is assumed to sustain the turbulence in the basin water (beneath the depths of the sills). With a flux Richardson number of 0.06, determined from investigations in many fjord basins, we find that a process‐based mixing model explains the observed mixing between the sills to within 90%.

Relationships between release season and feeding performance of hatchery-reared Japanese flounder Paralichthys olivaceus: In situ release experiment in coastal area of Wakasa Bay, Sea of Japan

Two groups of hatchery-reared juveniles of Japanese flounder Paralichthys olivaceus (Temminck and Shlegel) were experimentally released in Wada Beach, Fukui Prefecture, Japan and their feeding state examined in comparison to wild juveniles to investigate the optimal release season and the relationship between food availability and feeding performance of juveniles. We released two groups of 40,000 juveniles of ca. 50 mm size, one group in the early (29 May) and the other in late (2 July) seasons, periods with predicted high and low densities of prey mysids, respectively, although the abundance of mysids fluctuated markedly during the season. Food availability was higher for the early release group than the late release group. Although the main stomach contents of released and wild juveniles were mainly mysids and fish, the feeding state differed between the early and late release groups. The early release group had a stomach content index (SI) similar to that of the wild juveniles, but the SI of the late group was significantly less than that of the early release group and wild juveniles. The percentage of fish with empty stomachs was much higher in the late release group than in the other two groups. In addition, the density decrease rate was significantly more rapid for the late release group than the early release group. Clear correspondence between the food availability and feeding state of the released flounder juveniles indicates that the release of juveniles in an appropriate season when mysids are abundant is crucial for successful stocking.

Dissolution of montmorillonite in compacted bentonite by highly alkaline aqueous solutions and diffusivity of hydroxide ions

Highly alkaline environments induced by cementitious materials in radioactive waste repositories are likely to alter montmorillonite, the main constituent of bentonite buffer materials. Over long time periods, the alteration may cause the physical and/or chemical properties of the buffer to deteriorate. For the purpose of acquiring quantitative data to determine the effect of alteration on the permeability of a bentonite buffer, dissolution rates of montmorillonite and diffusivity of hydroxide ions in compacted sand–bentonite mixture specimens have been measured under highly alkaline, simulated groundwater conditions. Dissolution of montmorillonite was described by the linear dependence on time, W( t)= W(0)− R A t, under the employed experimental conditions of pH 13 to 14 and temperatures of 90 to 170 °C, where W( t) denotes the density of montmorillonite (mg of montmorillonite/m 3 of sand–bentonite mixture), W(0) the initial density, R A (Mg m −3 s −1) the rate of density decrease and t (s) the time after the contact with the simulated groundwater. R A is a function of pH and temperature (K), and expressed as R A=(0.013±0.007)exp[−(3.7±0.2)×10 4/ RT for the “pH 14.0” simulated groundwater, where R is the gas constant. The diffusivity of hydroxide ions was obtained in through-diffusion experiments combined with a pore diffusion model. The experiments were performed under relatively low temperatures of 10 to 50 °C to minimize the effect of alteration of bentonite. The effective diffusivity of hydroxide ions was in the order of 10 −10 to 10 −11 m 2/s, and is in the same order as those of Cl −, I − and tritiated water.

Location of structurally similar areas in chinchilla cochleas of different lengths.

In chinchillas, the length of the organ of Corti was found to vary by as much as 26% of the mean (18.31 mm). In specimens of different lengths, areas in which the basilar membrane and organ of Corti have the same physical dimensions were found to be located at the same percentage distance along the cochlear partition. Average densities of the inner and outer hair cells were noted to decrease with increasing cochlear length. However, the rate of decrease in density was less than the rate of increase in length. These findings indicate that long cochleas have a greater amount of the organ of Corti (and hence more sensory cells) in a given frequency region.

Topography of horizontal cells in the retina of the domestic cat.

Neurofibrillar methods stain a class of horizontal cells in the cat retina which are shown to be identical with the A-type horizontal cell of Golgi-staining. Thus all of the A-type cells of a single retina can be observed. On this basis the changes in density and dendritic field size of A-type horizontal cells with respect to retinal eccentricity were measured. The decrease in density from centre to periphery is balanced by a corresponding increase in size of the dendritic field. Consequently each retinal point--independent of retinal position--is covered by the dendritic fields of three of four A-type horizontal cells. The nuclei and nucleoli of B-type horizontal cells could also be recognized in neurofibrillar-stained material and thus their distribution was determined. The density ratio B-type: A-type is 2.8 +/- 0.4 and does not vary much from the centre to the periphery of the retina. Each retinal point is also covered by four B-type horizontal cells. Thus a single cone can contact a maximum of eight horizontal cells. The rate of density decrease from centre to periphery is closely similar in cones and horizontal cells but greater in ganglion cells.

Progressive Weathering of Submarine Basalt with Age: Further Evidence of Sea-Floor Spreading

Densities of layer 2 basalt recovered during the Deep Sea Drilling Project have been found to decrease steadily with age, a finding ascribed to progressive submarine weathering in the context of sea-floor spreading. The least-squares solution for 52 density measurements gives a rate of decrease in density of Δρ/Δ t = −0.46 × 10 −2 g per cm 3 m.y. = −16 percent per 100 m.y., which is in excellent agreement with earlier estimates based on observed chemical depletion rates of dredged oceanic basalt. Weathering of sea-floor basalt, should it penetrate to any considerable depth in layer 2, will decrease layer 2 seismic refraction velocities, act as a source of geothermal heat, and substantially influence the chemistry of sea water and the overlying column of sediment.

The Effect of Hydrostatic Pressure on the Shrinkage of Cavities in Metals

Specimens of magnesium, tough-pitch copper, and oxygen-free, high conductivity copper, in which cavities situated on grain boundaries had been introduced by creep, were subsequently annealed in an inert atmosphere over a range of temperatures and at atmospheric and higher pressures. The rate of density decrease on annealing, when cavities remained attached to grain boundaries, was associated with activation energies for the three materials of (1.0 ± 0.1) × 105, (1.34 ± 0.12) × 105, and (1.26 ± 0.12) × 105 J/mol, respectively, and these values were not significantly altered by environmental pressure up to 30 MN/m2 The decrease in sintering rate with time and the influence of hydrostatic pressure were consistent with a model of cavity closure by grain-boundary self-diffusion, which could also incorporate an effect of residual gas. The model of sintering was developed quantitatively, taking into account the effect of varying cavity size, and can be used to predict rates of sintering or, alternatively, to permit estimates of grain-boundary self-diffusion coefficients where data on these are not available.