Dust Devil Tracks

Dust devils that leave dark- or light-toned tracks are common on Mars and they can also be found on the Earth’s surface. Dust devil tracks (hereinafter DDTs) are ephemeral surface features with mostly sub-annual lifetimes. Regarding their size, DDT widths can range between ∼1 m and ∼1 km, depending on the diameter of dust devil that created the track, and DDT lengths range from a few tens of meters to several kilometers, limited by the duration and horizontal ground speed of dust devils. DDTs can be classified into three main types based on their morphology and albedo in contrast to their surroundings; all are found on both planets: (a) dark continuous DDTs, (b) dark cycloidal DDTs, and (c) bright DDTs. Dark continuous DDTs are the most common type on Mars. They are characterized by their relatively homogenous and continuous low albedo surface tracks. Based on terrestrial and martian in situ studies, these DDTs most likely form when surficial dust layers are removed to expose larger-grained substrate material (coarse sands of ≥500 μm in diameter). The exposure of larger-grained materials changes the photometric properties of the surface; hence leading to lower albedo tracks because grain size is photometrically inversely proportional to the surface reflectance. However, although not observed so far, compositional differences (i.e., color differences) might also lead to albedo contrasts when dust is removed to expose substrate materials with mineralogical differences. For dark continuous DDTs, albedo drop measurements are around 2.5 % in the wavelength range of 550–850 nm on Mars and around 0.5 % in the wavelength range from 300–1100 nm on Earth. The removal of an equivalent layer thickness around 1 μm is sufficient for the formation of visible dark continuous DDTs on Mars and Earth. The next type of DDTs, dark cycloidal DDTs, are characterized by their low albedo pattern of overlapping scallops. Terrestrial in situ studies imply that they are formed when sand-sized material that is eroded from the outer vortex area of a dust devil is redeposited in annular patterns in the central vortex region. This type of DDT can also be found in on Mars in orbital image data, and although in situ studies are lacking, terrestrial analog studies, laboratory work, and numerical modeling suggest they have the same formation mechanism as those on Earth. Finally, bright DDTs are characterized by their continuous track pattern and high albedo compared to their undisturbed surroundings. They are found on both planets, but to date they have only been analyzed in situ on Earth. Here, the destruction of aggregates of dust, silt and sand by dust devils leads to smooth surfaces in contrast to the undisturbed rough surfaces surrounding the track. The resulting change in photometric properties occurs because the smoother surfaces have a higher reflectance compared to the surrounding rough surface, leading to bright DDTs. On Mars, the destruction of surficial dust-aggregates may also lead to bright DDTs. However, higher reflective surfaces may be produced by other formation mechanisms, such as dust compaction by passing dust devils, as this may also cause changes in photometric properties. On Mars, DDTs in general are found at all elevations and on a global scale, except on the permanent polar caps. DDT maximum areal densities occur during spring and summer in both hemispheres produced by an increase in dust devil activity caused by maximum insolation. Regionally, dust devil densities vary spatially likely controlled by changes in dust cover thicknesses and substrate materials. This variability makes it difficult to infer dust devil activity from DDT frequencies. Furthermore, only a fraction of dust devils leave tracks. However, DDTs can be used as proxies for dust devil lifetimes and wind directions and speeds, and they can also be used to predict lander or rover solar panel clearing events. Overall, the high DDT frequency in many areas on Mars leads to drastic albedo changes that affect large-scale weather patterns

Yearly and seasonal variations of low albedo surfaces on Mars in the OMEGA/MEx dataset: Constraints on aerosols properties and dust deposits

The time variations of spectral properties of dark martian surface features are investigated using the OMEGA near-IR dataset. The analyzed period covers two Mars years, spanning from early 2004 to early 2008 (includes the 2007 global dust event). Radiative transfer modeling indicates that the apparent albedo variations of low to mid-latitude dark regions are consistent with those produced by the varying optical depth of atmospheric dust as measured simultaneously from the ground by the Mars Exploration Rovers. We observe only a few significant albedo changes that can be attributed to surface phenomena. They are small-scaled and located at the boundaries between bright and dark regions. We then investigate the variations of the mean particle size of aerosols using the evolution of the observed dark region spectra between 1 and 2.5 {\mu}m. Overall, we find that the observed changes in the spectral slope are consistent with a mean particle size of aerosols varying with time between 1 and 2 {\mu}m. Observations with different solar zenith angles make it possible to characterize the aerosol layer at different altitudes, revealing a decrease of the particle size of aerosols as altitude increases

Socio-demographic and health-related factors associated with cognitive impairment in the elderly in Taiwan

<p>Abstract</p> <p>Background</p> <p>Cognitive impairment is an age-related condition as the rate of cognitive decline rapidly increases with aging. It is especially important to better understand factors involving in cognitive decline for the countries where the older population is growing rapidly. The aim of this study was to examine the association between socio-demographic and health-related factors and cognitive impairment in the elderly in Taiwan.</p> <p>Methods</p> <p>We analysed data from 2119 persons aged 65 years and over who participated in the 2005 National Health Interview Survey. Cognitive impairment was defined as having the score of the Mini Mental State Examination lower than 24. The χ²test and multiple logistic regression models were used to evaluate the association between cognitive impairment and variables of socio-demography, chronic diseases, geriatric conditions, lifestyle, and dietary factors.</p> <p>Results</p> <p>The prevalence of cognitive impairment was 22.2%. Results of multivariate analysis indicated that low education, being single, low social support, lower lipid level, history of stroke, physical inactivity, non-coffee drinking and poor physical function were associated with a higher risk of cognitive impairment.</p> <p>Conclusion</p> <p>Most of the characteristics in relation to cognitive impairment identified in our analysis are potentially modifiable. These results suggest that improving lifestyle behaviours such as regular exercise and increased social participation could help prevent or decrease the risk of cognitive impairment. Further investigations using longitudinal data are needed to clarify our findings.</p

Use of statins and the risk of dementia and mild cognitive impairment: A systematic review and meta-analysis

We conducted a systematic review and meta-analysis to investigate whether the use of statins could be associated with the risk of all-caused dementia, Alzheimer’s disease (AD), vascular dementia (VaD), and mild cognitive impairment (MCI). Major electronic databases were searched until December 27th, 2017 for studies investigating use of statins and incident cognitive decline in adults. Random-effects meta-analyses calculating relative risks (RRs) were conducted to synthesize effect sizes of individual studies. Twenty-five studies met eligibility criteria. Use of statins was significantly associated with a reduced risk of all-caused dementia (k = 16 studies, adjusted RR (aRR) = 0.849, 95% CI = 0.787–0.916, p = 0.000), AD (k = 14, aRR = 0.719, 95% CI = 0.576–0.899, p = 0.004), and MCI (k = 6, aRR = 0.737, 95% CI = 0.556–0.976, p = 0.033), but no meaningful effects on incident VaD (k = 3, aRR = 1.012, 95% CI = 0.620–1.652, p = 0.961). Subgroup analysis suggested that hydrophilic statins were associated with reduced risk of all-caused dementia (aRR = 0.877; CI = 0.818–0.940; p = 0.000) and possibly lower AD risk (aRR = 0.619; CI = 0.383–1.000; p = 0.050). Lipophilic statins were associated with reduced risk of AD (aRR = 0.639; CI = 0.449–0.908; p = 0.013) but not all-caused dementia (aRR = 0.738; CI = 0.475–1.146; p = 0.176). In conclusion, our meta-analysis suggests that the use of statins may reduce the risk of all-type dementia, AD, and MCI, but not of incident VaD

Numerical interpretation of a mathematical model of membrane gas separation with energy transfer by gas flowing in a channel to gas penetrating this channel from the adjacent channel

Comparative calculations with a mathematical model designed by the authors, which takes into consideration energy transfer from gas flowing through a given channel to gas which penetrates this channel from an adjacent channel, as well as a model which omits this phenomenon, respectively, were made for the process of separating gas mixtures carried out with an inert sweep gas in the fourend capillary membrane module. Calculations were made for the process of biogas separation using a PMSP polymer membrane, relative to helium as the sweep gas. It was demonstrated that omitting the energy transfer in the mathematical model might lead to obtaining results which indicate that the capacity of the process expressed by the value of feed flux subjected to separation is by several percent higher than in reality

Mathematical modeling of gas mixtures separation using flat dense polymeric membranes

W pracy przedstawiono własny model matematyczny procesu separacji składników gazowych przy użyciu płaskiej nieporowatej membrany polimerowej. Model opisuje proces rozdziału dwóch składników gazowych przy udziale gazowego składnika odbierającego po drugiej stronie membrany. Zaprezentowano równania różniczkowe opisujące przebieg tego procesu, a także przedstawiono przykładowe wyniki obliczeń numerycznych dla rozdziału mieszaniny CH4 i CO2 (wzbogacanie biogazu) przy użyciu membrany wykonanej z PDMS.The paper presents the authors' own mathematical model of gas separation using a flat dense polymeric membrane. The model describes a separation process of two gaseous components with the presence of third gaseous component as a receiver on the other side of the membrane. Differential equations describing this process as well as some exemplary numerical calcula¬tion for the separation of CH4 and CO2 mixture (biogas enrichment) using a membrane made of PDMS are presented in the paper

Microfiltration with the feed containing air bubbles

Zbadano krzyżowy układ mikrofiltracyjny do zagęszczania zawiesin rozdrobnionego ciała stałego w cieczy zasilany nadawą płynącą wraz z pęcherzykami powietrza. Nie stwierdzono wpływu pęcherzyków na przebieg procesu, co oznacza, że pozytywne oddziaływanie pęcherzyków przejawiające się w zmywaniu osadu i negatywne przejawiające się w blokowaniu przez pęcherzyki dostępu cieczy do części powierzchni membrany, wzajemnie znoszą się. Wykazano też, że literaturowa zależność strumienia permeatu od stężenia zawiesiny dla nadawy dwufazowej jest aktualna także dla nadawy trójfazowej.Cross-flow microfiltration used for concentrating solid particles suspension with the addition of gas bubbles in the feed was investigated. The impact of gas bubbles on microfiltration process was not observed. This means that the positive impact of gas bubbles manifested in deposit washing from the membrane surface and the negative impact exhibited by blocking the liquid access to the membrane surface, cancel each other. It was proven that the literature relationship between permeate flow and suspension concentration for the two-phase feed is valid also for the three-phase feed

Investigation into the influence of process parameters on quality and quantity of water obtained from laundry wastewater

Mikrofiltracja pozwala na oczyszczenie ścieków pralniczych z zanieczyszczeń oraz odzysk części środków piorących i zawrócenie oczyszczonej wody do prania wstępnego w kolejnym cyklu pralniczym. Praca przedstawia ocenę wpływu parametrów procesowych, takich jak ciśnienie nadawy i strumień retentatu na szybkość powstawania permeatu i jego jakość. Zauważono, że jednoczesne uzyskanie dużych strumieni permeatu i wysokiej jakości permeatu jest niemożliwe. Praca wskazuje problem optymalizacyjny pozwalający na wybór, w określonych warunkach, optymalnego przepływu permeatu i optymalnej jego jakości.Microfiltration is a method for laundry wastewater treatment. It helps to remove impurities as well as to recover some detergents and to return purified water for prewashing in the next washing cycle. This work focuses on the assessment of impact of process parameters such as feed pressure and reténtate flow on the permeate flux and its quality. It was noticed that it is impossible to obtain simultaneously high permeate flux and high quality of permeate. The work indicates an optimization issue that allows the selection, in certain conditions, of optimal permeate flux and its optimal quality

Development of a new immobilized liquid membrane for separation of gaseous components

W pracy wykonano i przebadano własną membranę immobilizowaną(SLM) zbudowaną z mikroporowatej membrany polipropylenowej i oleju silikonowego. W tym celu opracowano metodę uzyskiwania modułów membranowych zawierających membrany SLM. Przeprowadzono badania z użyciem gazów 02, N2 i C02. Uzyskane wyniki wskazują, że tego typu membrana charakteryzuje się dużymi przepuszczalnościami, ale jednocześnie dość niskimi współczynnikami separacji.In this paper the authors' own SLM membrane is presented. For the purpose of this work a new immobilized membrane was prepared using a micropo- rous polypropylene membrane and silicone oil. A new method for obtaining such membrane modules was developed. Tests were conducted using such gases as 02, N2 and C02. The obtained results indicate that this type of mem-brane is characterized by large permeability factors but also by quite small separation factors

Modelling the gas flow in permeate channel in membrane gas separation process

This paper analyses the real behaviour of the fluid in the channels of a three-end membrane module. The commonly accepted mathematical model of membrane separation of gas mixtures in such modules assumes a plug flow of fluid through the feed channel and perfect mixing in the permeate channel. This article discusses the admissibility of accepting such an assumption regarding the fluid behaviour in the permeate channel. Throughout analysis of the values of the Péclet number criterion, it has been demonstrated that in the industrial processes of membrane gas separation, the necessary conditions for the perfect mixing in the permeate channel are not met. Then, CFD simulations were performed in order to establish the real fluid behaviour in this channel. It was proved that in the permeate channel the fluid movement corresponds to the plug flow, with the concentration differences at both ends of the module being insignificant. In view of the observations made, the admissibility of concentration stability assumptions in the mathematical models for the permeate channel was discussed