Searching for Magnetospheres around Herbig Ae/Be Stars

We describe four different approaches for the detection of magnetospheric accretion among Herbig Ae/Be stars with accretion disks. Studies of several unique objects have been carried out. One of the objects is the Herbig Ae star HD 101412 with a comparatively strong magnetic field. The second is the early-type Herbig B6e star HD 259431. The existence of a magnetosphere in these objects was not recognized earlier. In both cases, a periodicity in the variation of some line parameters, originating near the region of the disk/star interaction, has been found. The third object is the young binary system HD 104237, hosting a Herbig Ae star and a T Tauri star. Based on the discovery of periodic variations of equivalent widths of atmospheric lines in the spectrum of the primary, we have concluded that the surface of the star is spotted. Comparing our result with an earlier one, we argue that these spots can be connected with the infall of material from the disk onto the stellar surface through a magnetosphere. The fourth example is the Herbig Ae/Be star HD 37806. Signatures of magnetospheric accretion in this object have been identified using a different method. They were inferred from the short-term variability of the He i λ5876 line profile forming in the region of the disk/star interaction.

Effect of dexamethasone on daily fetal movement, umbilical and middle cerebral arteries Doppler and cardiotocogram

Background: Preterm birth is a leading cause of perinatal death and disability and is an important public health problem globally. There is more work to be done regarding steroids effect, especially with the variations among demography and pathological conditions affecting mothers. The aim of this study was to investigate the effect of dexamethasone on healthy fetuses, observing the effects on MCA and UA Doppler velocity waveforms and cardiotocography, correlating them with fetal movement.Methods: This prospective cross-sectional study was conducted in Ain Shams University Maternity Hospital, starting from April 2020 till December 2020. One hundred and ten women was recruited for the study. All women undergo elective cesarean section before 39 weeks of gestation. UA and MCA Doppler values were taken; nonstress test was recorded and fetal movements were counted after a single course of dexamethasone.Results: Our results included decrease in MCA PI, decrease in foetal movement count on the second day of dexamethasone injection, increase of short-term variability and direct correlation between the MCA RI and UA PI with the fetal movements decrease on the 5th day of dexamethasone injection.Conclusions: There are definitely cardiovascular changes that occur after dexamethasone administration, presented by increase in MCA blood flow and increase in FHR short term variability.

Sea surface salinity short-term variability in the tropics

Using data from the Global Tropical Moored Buoy Array, we study the validation process for satellite measurement of sea surface salinity (SSS). We compute short-term variability (STV) of SSS, variability on timescales of 2–17 d. It is a proxy for subfootprint variability over a 100 km footprint as seen by a satellite measuring SSS. We also compute representation error, which is meant to mimic the SSS satellite validation process where footprint averages are compared to pointwise in situ values. We present maps of these quantities over the tropical array. We also look at seasonality in the variability of SSS and find which months have maximum and minimum amounts. STV is driven at least partly by rainfall. Moorings exhibit larger STV during rainy periods than during non-rainy ones. The same computations are also done using output from a high-resolution global ocean model to see how it might be used to study the validation process. The model gives good estimates of STV, in line with the moorings, although tending to have smaller values.

Short-Term Variability in Alaska Ice-Marginal Lake Area: Implications for Long-Term Studies

Lakes in direct contact with glaciers (ice-marginal lakes) are found across alpine and polar landscapes. Many studies characterize ice-marginal lake behavior over multi-decadal timescales using either episodic ~annual images or multi-year mosaics. However, ice-marginal lakes are dynamic features that experience short-term (i.e., day to year) variations in area and volume superimposed on longer-term trends. Through aliasing, this short-term variability could result in erroneous long-term estimates of lake change. We develop and implement an automated workflow in Google Earth Engine to quantify monthly behavior of ice-marginal lakes between 2013 and 2019 across south-central Alaska using Landsat 8 imagery. We employ a supervised Mahalanobis minimum-distance land cover classifier incorporating three datasets found to maximize classifier performance: shortwave infrared imagery, the normalized difference vegetation index (NDVI), and spatially filtered panchromatic reflectance. We observe physically-meaningful ice-marginal lake area variance on sub-annual timescales, with the median area fluctuation of an ice-marginal lake found to be 10.8% of its average area. The median signal (slow lake growth) to noise (physically-meaningful short-term area variability) ratio is 1.5:1, indicating that short-term variability is responsible for ~33% of observed area change in the median ice-marginal lake. The magnitude of short-term area variability is similar for ice-marginal and nonglacial lakes, suggesting that the cause of observed variations is not of glacial origin. These data provide a new context for interpreting behaviors observed in multi-decadal studies and encourage attention to sub-annual behavior of ice-marginal lakes even in long-term studies.

Seasonal Evolution of Cape Darnley Bottom Water Revealed by Mooring Measurements

This study examines the seasonal evolution of Cape Darnley Bottom Water (CDBW), using the results of mooring and hydrographic measurements in the slope region off Cape Darnley in 2008–2009 and 2013–2014. Newly formed CDBW began reaching the western and nearshore part of the slope region off Cape Darnley in April, spread to the offshore and eastern part in May, and reached the easternmost part in September. The potential temperature and salinity decreased and the neutral density increased when newly formed CDBW reached mooring sites. Potential temperature-salinity properties of CDBW changed over time and location. The salinity of the source water of CDBW estimated from potential temperature-salinity diagrams started to increase at a nearshore mooring in late April, which is about 2 months after the onset of sea-ice production, and continued to increase during the ice production season. It is most probable that the accumulation of brine in the Cape Darnley polynya produces the seasonal variation of potential temperature-salinity properties of CDBW. Two types of CDBW were identified. Cold and less saline CDBW and warm and saline CDBW were present in Wild and Daly Canyons, respectively. This indicates that the salinity of the source water of CDBW increased in the westward direction. CDBW exhibited short-term variability induced by baroclinic instability.

Contoured Vertical Distribution and Spatio-temporal Variation of an Intertidal Macroalgal Assemblage in King George Island, Antarctica

Short-term variability, spatial variability, and the vertical distribution of an intertidal macroalgal assemblage were examined on the coast of Barton Peninsula, Maxwell Bay, King George Island, Antarctica. Sampling was performed during the three austral summer seasons from November 2016 to January 2019. The sampling interval for short-term variability was 1–2 months. Sampling for spatial variability was performed at two sites 400 m apart. Eighteen algal species were identified, with 75% relative coverage of the predominant red Iridaea cordata and endemic brown Phaeurus antarcticus. Summer abundance can be described as a shift from I. cordata to P. antarcticus, and the change in color is intuitively presented using a contour plot for the first time. Short-term variation in the macroalgal assemblage showed 78.35% similarity between one month and 64.61% similarity between two months. The spatial variation analysis indicated 77.13% similarity between the assemblage at the two sites. If global warming continues, the algal population of this region is expected to expand. P. antarcticus, which is primarily found in the subtidal zone, is predicted to relocate southward or higher in the near future. Long-term monitoring of this research region, which is dominated by the two species, is warranted to determine the impact of global warming on the macroalgal assemblage.

Sea Surface Salinity Short Term Variability in the Tropics

Using data from the Global Tropical Moored Buoy Array we study the validation process for satellite measurement of sea surface salinity (SSS). We compute short-term variability (STV) of SSS, variability on time scales of 5–14 days. It is meant to be a proxy for subfootprint variability as seen by a satellite measuring SSS. We also compute representation error, which is meant to mimic the SSS satellite validation process where footprint averages are compared to pointwise in situ values. We present maps of these quantities over the tropical array. We also look at seasonality in the variability of SSS and find which months have maximum and minimum amounts. STV is driven at least partly by rainfall. Moorings exhibit larger STV during rainy periods than non-rainy ones. The same computations are also done using output from a high-resolution global ocean model to see how it might be used to study the validation process. The model gives good estimates of STV, in line with the moorings, though tending to have smaller values.