Relative Temporal Changes Research Articles

Radio Absorption in the Nightside Ionosphere of Mars During Solar Energetic Particle Events

AbstractCharacterization, understanding, and prediction of the Martian radio environment are of increasing importance to the forthcoming human exploration of Mars. Here we investigate 3–5 MHz radio absorption in the nightside ionosphere of Mars caused by enhanced ionization at <100 km altitudes during solar energetic particle (SEP) events. We conduct a quantitative analysis of radio absorption and SEP flux data that have been accumulated by two spacecraft currently orbiting Mars, thereby demonstrating that radio absorption is clearly correlated with SEP fluxes. A comparison of the observations with radio absorption properties predicted by a numerical model indicates that the relative temporal changes, radio frequency dependence, and SEP energy dependence of the observed radio absorption are in agreement with the model prediction. Meanwhile, the model systematically overestimates the radio absorption in the ionosphere by a factor of 3.7. We explore several sources of uncertainty, including the electron‐neutral collision frequency, absolute sensitivity of the SEP instrument, and limited transport of SEPs to the atmosphere, but the ultimate cause of the systematic discrepancy between the measured and modeled radio absorption is yet to be identified. Further efforts should be put into the development of a comprehensive and observationally validated model of radio absorption in the Martian ionosphere to assist the future crew and spacecraft activities on the surface of Mars.

Rapid Magnetic Susceptibility Characterization of Coastal Morphosedimentary Units at Two Insular Strandplains in Estonia

Coastal archives of changing hydrometeorological conditions include mineralogical anomalies, such as heavy-mineral concentrations (HMCs) of variable thickness and intensity, which contain varying ferrimagnetic (e.g., magnetite) fractions. As an effective alternative to laborious mineralogical and granulometric analysis, we present the first set of bulk-volume low-field magnetic susceptibility (MS) databases from beach and dune lithosomes in the Western Estonian archipelago: Harilaid cuspate foreland (westernmost Saaremaa Island) and Tahkuna strandplain (northernmost Hiiumaa Island). Readings were conducted both in situ from trench walls and on core subsamples. At the Tahkuna site, late Holocene beach ridges reveal substantially lower values: quartz-dominated dune sequences grade from 5–20 μSI downward to diamagnetically dominated (−1–7 μSI) beach facies. Values are higher (20–140 μSI) in historically reactivated parabolic dunes that are encroaching southward over the strandplain. At the Harilaid site, four beach dune ridges (height: 2–3 m) that span the past 250–300 years show a general increase in mean MS from 320–850 μSI with decreasing age, with peaks of 1000–2000 μSI below the dune crests (depth: ~0.3–0.6 m) likely related to contemporary wind acceleration during ridge aggradation. The highest mineralogical anomalies range from 2000–5500 μSI in the historic dune sections and exceed 8000 μSI along the actively eroding upper-berm segments, typical of HMCs generated by moderate storms. MS anomalies are likely correlated with high-amplitude electromagnetic signal responses in georadar records and provide useful information for optical luminescence sampling strategies. Our study demonstrates that magnetic susceptibility trends provide a useful means of rapidly assessing relative temporal changes in overall wave/wind climates, help identify and correlate discrete anomalies related to extreme events, serve as local beach/dune boundary indicators, and represent potentially quantifiable paleo-energy indices.

A metatranscriptomic approach to explore longitudinal tissue specimens from non-healing diabetes related foot ulcers.

Cellular mechanisms and/or microbiological interactions which contribute to chronic diabetes related foot ulcers (DRFUs) were explored using serially collected tissue specimens from chronic DRFUs and control healthy foot skin. Total RNA was isolated for next‐generation sequencing. We found differentially expressed genes (DEGs) and enriched hallmark gene ontology biological processes upregulated in chronic DRFUs which primarily functioned in the host immune response including: (i) Inflammatory response; (ii) TNF signalling via NFKB; (iii) IL6 JAK‐STAT3 signalling; (iv) IL2 STAT5 signalling and (v) Reactive oxygen species. A temporal analysis identified RN7SL1 signal recognition protein and IGHG4 immunoglobulin protein coding genes as being the most upregulated genes after the onset of treatment. Testing relative temporal changes between healing and non‐healing DRFUs identified progressive upregulation in healed wounds of CXCR5 and MS4A1 (CD20), both canonical markers of lymphocytes (follicular B cells/follicular T helper cells and B cells, respectively). Collectively, our RNA‐seq data provides insights into chronic DRFU pathogenesis.

Trends in Geographic Sensitivity of Marine Fishes Over Decades in the North Sea

Accounting for biotic interactions is important for predicting species and ecosystem variation under changing climate but difficult to achieve in practice. The proportion of geographical overlap between species, called species geographical sensitivity (SGS), could be used to gauge the potential for species interactions. Species with increasingly high SGS could have the potential to experience more interactions with other species and vice versa, which might have important implications in ecological assessment, particularly at a community level, in the face of climate change. We compiled fish occurrences in the North Sea from 1983 to 2020 and calculated annual mean SGS (mSGS) to systematically evaluate their temporal changes and to estimate influences of species traits on the relative temporal changes in mSGS. The results showed that 36.3% of species significantly changed their mSGS over time, with high correlations between changes in species range size and overlap with other species. The species’ averaged mSGS before warming was highly correlated with the relative change in mSGS. Depth range, body length, and age at maturity together explained most variation in mSGS among these species. Contemporary climate change is expected to reorganize species distributions and interactions and substantially alter marine ecosystem functioning. Our assessment opens a new avenue for evaluating climate change impacts on species geographical interactions, and such geographical changes may be contingent on species traits.

Dynamical characteristics of global stock markets based on time dependent Tsallis non-extensive statistics and generalized Hurst exponents

We perform non-linear analysis on stock market indices using time-dependent extended Tsallis statistics. Specifically, we evaluate the q-triplet for particular time periods with the purpose of demonstrating the temporal dependence of the extended characteristics of the underlying market dynamics. We apply the analysis on daily close price timeseries of four major global markets (S&P 500, Tokyo-NIKKEI, Frankfurt-DAX, London-LSE). For comparison, we also compute time-dependentGeneralized Hurst Exponents (GHE) Hq using the GHE method, thus estimating the temporal evolution of the multiscaling characteristics of the index dynamics. We focus on periods before and after critical market events such as stock market bubbles (2000 dot.com bubble, Japanese 1990 bubble, 2008 US real estate crisis) and find that the temporal trends of q-triplet values significantly differ among these periods indicating that in the rising period before a bubble break, the underlying extended statistics of the market dynamics strongly deviates from purely stochastic behavior, whereas, after the breakdown, it gradually converges to the Gaussian-like behavior which is a characteristic of an efficient market. We also conclude that relative temporal variation patterns of the Tsallis q-triplet can be connected to different aspects of market dynamics and reveals useful information about market conditions especially those underlying the development of a stock market bubble. We found specific temporal patterns and trends in the relative variation of the indices in the q-triplet that distinguish periods just before and just after a stock-market bubble break. Differences between endogenous and exogenous stock market crises are also captured by the temporal changes in the Tsallis q-triplet. Finally, we introduce two new time-dependent empirical metrics (Q-metrics) that are functions of the Tsallis q-triplet. We apply them to the above stock market index price timeseries and discuss the significance of their temporal dependence on market dynamics and the possibility of using them, together with the relative temporal changes of the q-triplet, as signaling tools for future market events such as the development of a market bubble.

Identification of the heart wall and chamber based on temporal change of ultrasonic scatterer distribution

In most current methods for evaluating the cardiac function by ultrasound, the heart wall area is identified manually by an examiner. To eliminate examiner dependence and to improve usability, an automatic heart wall identification method is desirable. Identification based on only echogenicity often fails because of low echogenicity of some areas of the heart wall. In the present study, to determine more essential features, we focused on the relative temporal change of ultrasonic scatterer distribution and proposed three features for identification of the heart wall and the chamber: cross-correlation of RF signals, that of envelopes, and spatial dispersion of movement vectors in small regions. In an in vivo experiment, using echogenicity and the three features, we identified the heart wall and the chamber in the left ventricular long-axis view, resulting in criteria of separability J of 1.69, 1.40, and 3.02 using these features compared with the result of 0.979 using echogenicity.

Stroke in right dorsal anterior insular cortex Is related to myocardial injury.

Elevated levels of cardiac troponin, and especially their relative changes over time, indicate acute myocardial injury. They are also frequently observed after acute ischemic stroke (AIS), indicating poor functional outcome and increased mortality. However, recent evidence showed that, in most AIS patients, myocardial injury is not caused by coronary ischemia. Instead, stroke lesion location has been suggested to precipitate myocardial injury. Voxel-based lesion-symptom mapping (VLSM) was used in 299 patients who had a magnetic resonance imaging-confirmed acute ischemic stroke within the anterior circulation and a high-sensitivity cardiac troponin T (hs-cTnT) acquired on the day of admission. Of these, 228 had a second troponin measurement during the acute phase. The absolute hs-cTnT levels above the 99th percentile of a healthy reference population (≥14ng/l) as well as their relative temporal changes were used as continuous variables of interest in the VLSM model, including a multiple regression analysis adjusted for confounding variables. The anterior insular cortex of the right hemisphere, in particular its dorsal subregion, was significantly associated with the relative temporal changes of hs-cTnT (p < 0.01, corrected for multiple comparisons). In contrast, the baseline hs-cTnT levels on admission were not related to lesion location anywhere within the anterior circulation. Our results amplify recent evidence from functional neuroimaging, which suggests a prominent role of dorsal anterior insular cortex in the parasympathetic control of cardiac and autonomic function. Acute vascular damage of this insular subregion might lead to autonomic dysbalance and an upregulation of sympathetic function, thereby resulting in myocardial injury. Ann Neurol 2017;81:502-511.

Dynamic changes in myeloid derived suppressor cell subsets following renal transplant: A prospective study

BackgroundMyeloid-derived suppressor cells (MDSC) are powerful suppressors of immune responses. MDSC numbers are increased in some renal transplant recipients (RTR) and there is increasing interest in their potential role in promoting both transplant tolerance and transplant associated malignancy. However the factors influencing MDSC mobilisation are unknown, and the relative temporal changes in the granulocytic (G-MDSC) and monocytic (Mo-MDSC) subsets of MDSC have not been defined. MethodsThe circulating frequencies of MDSC and dendritic cells (DC) were analysed by multicolour flow cytometry in RTR (n=8) prior to transplant and at regular intervals out to 1year post-transplant. ResultsIn RTRs, numbers of both G-MDSC and Mo-MDSC increased rapidly following transplant and peaked within 8days, whilst DC numbers decreased. A second peak in G-MDSC numbers was observed in 7/8 patients within 3months and 2 patients had a further 3rd peak in G-MDSC numbers which, in one patient, corresponded to a rejection event. Mo-MDSC numbers underwent less fluctuation and a subsequent peak in numbers was observed in only 2/8 patients. Respective kidney donors (n=5) underwent only small transient increases in MDSC following surgery. Overall, there was little correlation between increases in MDSC and the occurrence of detectable clinical events or treatment changes. ConclusionsIn RTRs, MDSC numbers increase rapidly and peak following commencement of immunosuppression, but then fluctuate in response to as yet undefined stimuli. Further studies are required to identify the factors modulating MDSC mobilisation.

Macro‐moth families differ in their attraction to light: implications for light‐trap monitoring programmes

Abstract Light traps are used to make inferences about local macro‐moth communities, but very little is known about the efficiency with which they attract moths from varying distances, and how this may differ among families. We released 731 marked individuals, from three of the most common and species‐rich macro‐moth families, at several distances from low‐wattage actinic light traps in open and woodland habitat. Logistic regression showed family‐specific sampling areas: erebids were attracted from up to 27 m, geometrids from up to 23 m, and noctuids from up to 10 m from the light source, with these distances corresponding to a 5% recapture rate. Sampling size was also family‐specific: a maximum of 55% of erebids, 15% of geometrids, and 10% of noctuids were predicted to be trapped when flying near (0–1 m) light traps. Our study demonstrates that weak light traps: (i) have remarkably local sampling ranges, resulting in samples that are highly representative of the local habitat, and (ii) attract small, and family‐specific proportions of individuals within these ranges. We suggest that the local sampling ranges of weak light traps make them excellent tools to monitor nocturnal macro‐moth communities. As trap efficiency differs among macro‐moth families, care must be taken in relating the abundance of the sample to absolute local abundance. Frequent sampling can provide adequate data on relative temporal change in the local macro‐moth fauna, however.

Study on the relative local temporal changes of the geomagnetic field on the Lublin slope of the East European Craton (the Parczew – Chełm profile)

The local relative changes of the total intensity geomagnetic field in time are presented against the background of the geological structure of Lublin-Podlasie slope (LPSK) of the East European Craton. The research concerned measurement results of the total intensity (T) of the geomagnetic field, taken in the last 12 years (1997–2008) at 20 sites located along the Parczew – Chelm profile. Relative temporal changes of the geomagnetic field were determined on the basis of values of geomagnetic field calculated with reference to geomagnetic field measured at the base. These changes are presented as graphs, and in the form of space-time 2D and 3D representations, showing their relationship with the magnetic anomaly map. The cause of local relative changes was attempted to be explained by 2D magnetic modeling assuming that the changes of the induced magnetization of the basement crystalline rocks are result of the geomagnetic secular variations.

Palaeo-ice streams in the Foxe/Baffin sector of the Laurentide Ice Sheet

In this paper, we describe mapping of palaeo-ice streams in the Foxe/Baffin sector of the Laurentide Ice Sheet by means of geomorphological interpretation of high-resolution satellite images. Our interpretations were guided by a glaciological inversion scheme, aided by digital elevation models, publicly available sonar surveys and field studies. As a result, we produced a map depicting the location, geometry and relative temporal changes of palaeo-ice streams and analysed their palaeoglaciological implications for the Foxe/Baffin sector. We conclude that in the period between the Last Glacial Maximum and approximately 7.0 kyr BP, the Foxe/Baffin sector was largely drained by topographically controlled outlet glaciers and ice streams, which were organized in a relatively stable pattern. During this time, large areas of Melville Peninsula and central Baffin Island were subject to cold-based conditions. Between 7.0 and 6.0 kyr BP, the Foxe/Baffin sector collapsed catastrophically in the Foxe Basin, after which its remnant portion became confined to Baffin Island. During this collapse, rapid successions of small transient ice streams occurred along wide, loosely defined topographical corridors in two sectors of Baffin Island. The presently available landform archive on emerged land is not sufficient to conclusively support the existence of fully scaled ice streams along the whole length of Hudson Strait. As an alternative solution, we propose that topographically controlled ice streams might have occurred along the deepest parts of Hudson Strait, with attendant cold-based ice zones on marginal areas and islands at the head of the strait.

Determination of aortic compliance from magnetic resonance images using an automatic active contour model

The possibility of monitoring changes in aortic elasticity in humans has important applications for clinical trials because it estimates the efficacy of plaque-reducing therapies. The elasticity is usually quantified by compliance measurements. Therefore, the relative temporal change in the vessel cross-sectional area throughout the cardiac cycle has to be determined. In this work we determined and compared the compliance between three magnetic resonance (MR) methods (FLASH, TrueFISP and pulse-wave). Since manual outlining of the aortic wall area is a very time-consuming process and depends on an operator's variability, an algorithm for the automatic segmentation of the artery wall from MR images through the entire heart cycle is presented. The reliable detection of the artery cross-sectional area over the whole heart cycle was possible with a relative error of about 1%. Optimizing the temporal resolution to 60 ms we obtained a relative error in compliance of about 7% from TrueFISP (1.0 × 1.0 × 10 mm3, signal-to-noise ratio (SNR) > 12) and FLASH (0.7 × 0.7 × 10 mm3, SNR > 12) measurements in volunteers. Pulse-wave measurements yielded an error of more than 9%. In a study of ten volunteers, a compliance between C = 3 × 10−5 Pa−1 and C = 8 × 10−5 Pa−1 was determined, depending on age. The results of the TrueFISP and the pulse-wave measurements agreed very well with one another (confidence interval of 1 × 10−5 Pa−1) while the results of the FLASH method more clearly deviated from the TrueFISP and pulse-wave (confidence interval of more than 2 × 10−5 Pa−1).

The Visual Looming Navigation Cue: A Unified Approach

Visual looming is related to an increasing projected size of an object on a viewer's retina as the relative distance between the viewer and the object decreases. It is an indication for threat that may be used along with visual fixation to accomplish navigation tasks. This paper defines visual looming as the time derivative of the relative distance (range) between the observer and the object divided by the relative distance itself. It introduces a unified approach to visual looming by showing how visual looming can be calculated from the relative temporal change in the following attributes of a 2D image sequence: (i) image area, (ii) image brightness, (iii) texture density in the image, and (iv) image blur. It is shown that a closed-form unified expression can be adopted in all these methods. Experimental results illustrate how the measured values of looming are related to the actual values. Finally, looming is used in the sense of a threat of collision, along with visual fixation, to navigate in an unknown environment.

Evidence for Induction of Interferon-α and Interferon-β in Retinal Glial Cells of Müller

Studies were performed to determine if retinal glial cells of Müller transcribe the genes for interferon-α (IFNα) or IFNβ upon exposure to virus. Responses to herpes simplex virus type 1 (HSV-1) were tested with cultured murine Müller cells and,in vivo,with retinas obtained after bilateral injection of either HSV-1 or buffer into the anterior chamber of the eyes of BALB/c mice. Induction of IFN transcription and relative temporal changes in transcript levels occurred over time after eitherin vitroorin vivoexposure to HSV-1. Transcription of both IFN genes was induced in cultured glia within 1 hr after exposure to virus. IFN transcripts were detected in retinas by 24 hr postinfection and these were maximal at 3 days. Byin situhybridization (ISH), IFNα2mRNA localized to focal areas in the intact retinas of virus-injected eyes and was consistent with our previous report of a transient, focal appearance of viral antigens in those retinas. Uninfected cells and ocular tissues were negative for IFN transcripts. Combined ISH and immunohistochemistry on retinal impression smears confirmed that glial fibrillary acidic protein-positive Müller cells are an intraretinal source of IFNα and IFNβ transcripts after ocular exposure to HSV-1. Our results support a role for Müller cells as participants in intraretinal antiviral or immunomodulatory responses via type 1 IFN production and may have implications for future therapeutic interventions.