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

Early Detection of t(8;21) Chromosomal Translocations During Treatment of PML-RARA Positive Acute Promyelocytic Leukemia: A Case Study

Here we describe a female patient who developed acute promyelocytic leukemia (APL) characterized by t(l5;17) translocation at diagnosis. The patient began treatment with all-trans retinoic acid (ATRA) + chemotherapy. During follow up, the patient was found to be negative for the t(15;17) transcript after 3 months of therapy which remained undetectable, thereafter. However, the emergence of a small clone with a t(8;21) abnormality was observed in the bone marrow and peripheral blood (PB) cells between 3 and 18 months following treatment initiation. The abnormal translocation observed in PB cells obtained at 3 months was detected after the second cycle of consolidation therapy and reappeared at 15 months during maintenance treatment, a period without ATRA. Although based on a single case, we conclude that genetic screening of multiple translocations in AML patients should be requested to allow early identification of other emerging clones during therapy that may manifest clinically following treatment

Dust Devil Populations and Statistics

The highly-skewed diameter and pressure drop distributions of dust devils on Earth and Mars are noted, and challenges of presenting and comparing different types of observations are discussed. The widely- held view that Martian dust devils are larger than Earth\u27s is critically-assessed: the question is confounded somewhat by different observation techniques, but some indication of a ~3x larger population on Mars is determined. The largest and most intense (in a relative pressure sense) devils recorded are on Mars, although the largest reported number density is on Earth. The difficulties of concepts used in the literature of \u27average\u27 diameter, pressure cross section, and area fraction are noted in the context of estimating population-integral effects such as dust lifting

Shifts in dynamic regime of an invasive lady beetle are linked to the invasion and insecticidal management of its prey

The spread and impact of invasive species may vary over time in relation to changes in the species itself, the biological community of which it is part, or external controls on the system. Here we investigate whether there have been changes in dynamic regimes over the last 20 years of two invasive species in the Midwestern US, the multicolored Asian lady beetle Harmonia axyridis and the soybean aphid, Aphis glycines. We show by model selection that after its 1993 invasion into the American Midwest, the year-to-year population dynamics of H. axyridis were initially governed by a logistic rule supporting gradual rise to a stable carrying capacity. After invasion of the soybean aphid in 2000, food resources at the landscape level became abundant, supporting a higher year-¬to-year growth rate, and a higher but unstable carrying capacity, with 2-year cycles in both aphid and lady beetle abundance as a consequence. During 2005-2007, farmers in the Midwest progressively increased their use of insecticides for managing A. glycines, combining prophylactic seed treatment with curative spraying based on thresholds. This human intervention dramatically reduced the soybean aphid as a major food resource for H. axyridis at landscape level, and corresponded to a reverse shift towards the original logistic rule for year-to-year dynamics. Thus, we document a short episode of major predator-prey fluctuations in an important agricultural system resulting from two biological invasions that were apparently damped by widespread insecticide use. Recent advances in development of plant resistance to A. glycines in soybeans may mitigate the need for pesticidal control and achieve the same stabilization of pest and predator populations at lower cost and environmental burden