bluuebunny/crossref_metadata_2025 huggingface dataset:
Linear Turán Numbers of Linear Cycles and Cycle-Complete Ramsey Numbers
Authors: COLLIER-CARTAINO CLAYTON , GRABER NATHAN , JIANG TAO
Published: April 2018

Anr-uniform hypergraph is called anr-graph. A hypergraph islinearif every two edges intersect in at most one vertex. Given a linearr-graphHand a positive integern, thelinear Turán numberexL(n,H) is the maximum number of edges in a linearr-graphGthat does not containHas a subgraph. For each ℓ ≥ 3, letCrℓdenote ther-uniform linear cycle of length ℓ, which is anr-graph with edgese1, . . .,eℓsuch that, for alli∈ [ℓ−1], |ei∩ei+1|=1, |eℓ∩e1|=1 andei∩ej= ∅ for all other pairs {i,j},i≠j. For allr≥ 3 and ℓ ≥ 3, we show that there exists a positive constantc=cr,ℓ, depending onlyrand ℓ, such that exL(n,Crℓ) ≤cn1+1/⌊ℓ/2⌋. This answers a question of Kostochka, Mubayi and Verstraëte [30]. For even ℓ, our result extends the result of Bondy and Simonovits [7] on the Turán numbers of even cycles to linear hypergraphs.

Using our results on linear Turán numbers, we also obtain bounds on the cycle-complete hypergraph Ramsey numbers. We show that there are positive constantsa=am,randb=bm,r, depending only onmandr, such that\begin{equation} R(C^r_{2m}, K^r_t)\leq a \Bigl(\frac{t}{\ln t}\Bigr)^{{m}/{(m-1)}} \quad\text{and}\quad R(C^r_{2m+1}, K^r_t)\leq b t^{{m}/{(m-1)}}. \end{equation}
Risk allele of gene variant rs6584389 is associated with increased intima-media thickness in patients with type 2 diabetes
Authors: Kozarova Miriam , Malachovska Zuzana , Zidzik Jozef , Javorsky Martin , Demkova Katarina , Habalova Viera , Tkac Ivan
Published: April 2018

Abstract. Background: Genome-wide association studies identified several gene variants associated with peripheral arterial disease (PAD). Among them, rs6584389 A>C was significantly associated with PAD defined by decreased ankle-brachial index (ABI). The aim of this study was to investigate whether the rs6584389 variant is also associated with the earlier stages of atherosclerosis assessed by intima-media thickness (IMT) or pulse-wave velocity (PWV) in clinically asymptomatic subjects with type 2 diabetes (T2DM), a group of patients with a high cardiovascular risk. Patients and methods: In total, 111 patients with T2DM (56 females, 55 males) with a mean age 63.0 ± 9.1 years were consecutively included in the study. IMT was measured by ultrasound using 7 MHz linear transducer. PWV was measured using a piezoelectric method. Genotyping for rs6584389 was performed by PCR-HRMA method. Results: The carriers of the risk C-allele of rs6584389 variant had significantly higher mean left-side IMT (AA: 0.67 ± 0.12, AC 0.77 ± 0.21, CC 0.78 ± 0.22 mm; p = 0.04). In multiple linear regression analysis, rs6586389 genotype was significantly associated with all measured IMT parameters. The presence of each risk C-allele predicted an increase in left-side IMT by 0.056 mm (p = 0.017), right-side IMT by 0.053 mm (p = 0.039), average IMT by 0.054 mm (p = 0.023), and maximal IMT by 0.058 mm (p = 0.021). Age and HbA1c levels were also significantly associated with increased IMT in all multivariate models. Conclusions: Gene variant rs6584389 A>C near to PAX2 gene was associated with increased carotid IMT in patients with type 2 diabetes independently of the other main risk factors for atherosclerosis.
Low‐Latitude Ionospheric Density Irregularities and Associated Scintillations Investigated by Combining COSMIC RO and Ground‐Based Global Positioning System Observations Over a Solar Active Period
Authors: Yang Zhe , Liu Zhizhao
Published: April 2018

This study for the first time presents a locally integrated analysis of occurrences of ionospheric E and F region irregularities/scintillations in southeast China, by employing radio occultation (RO) profile data retrieved from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites and observations from a ground‐based Global Navigation Satellite System receiver over a solar active period from 2014 to 2015. Their occurrences in both nighttime and daytime were examined by using both amplitude scintillation index (S4) and the rate of change of total electron content index. It is found that (1) F region irregularities occurred predominantly during 20–03 local time (LT) and exhibited maximum (minimum) during equinoxes (solstices) and equinoctial (solstice) asymmetry. Their geographic mapping reveals the maximum occurrence in the westward tilted structure of equatorial plasma bubbles. In addition, the altitude‐time variations indicate that their occurrences at higher altitudes were prevailing at 20–22 LT. (2) The E region irregularities were found prominently during 15–00 LT at altitudes of 90–110 km with an even geographic distribution. Their occurrences with maximum in summer (May–August) were distinctly detected by RO observations but insignificantly by ground‐based observations. (3) By examining simultaneous observations of E and F region irregularities, it is found that they appeared absent during 21–00 LT and predominant after midnight. This could be related to the weakening/disruption of sporadic E (Es) layers during the development of equatorial plasma bubbles. A sign of coupling of E and F regions during nighttime is likely revealed from RO profile data.
ELF Whistler Dependence on a Sunlit Ionosphere
Authors: Fritz Bruce A. , Heavisides John , Young Matthew A. , Kim Hyomin , Lessard Marc R.
Published: April 2018

Narrow bandwidth, whistler‐like spectral features in the extremely low frequency (ELF) range were recorded at South Pole Station over the duration of 2004. A full year of observation shows a distinct lack of activity over the Antarctic winter season. A calculation of solar zenith angle at the time of detection illustrates a connection between the occurrence of ELF whistlers and a sunlit ionosphere. ELF whistlers detected at low latitude follow a similar general trend between ELF whistler occurrence rate and changing solar zenith angle, but with an additional persistence of detections after local sunset. Temporal profiles from the International Reference Ionosphere 2016 show that the peaks in ELF whistler occurrence align with times of changing ionospheric composition. Correlation with solar activity per the F10.7 index shows no connection to daily variations in activity, and the consistency of solar flux levels throughout 2004 appears insufficient to explain the absence of events during the winter blackout. These observations place new physical constraints on the conditions necessary for detecting ELF whistlers and suggest the potential for localized generating mechanisms due to plasma instabilities in the ionosphere.
Statistical Analysis of the Electron Density Gradients in the Polar Cap F Region Using the Resolute Bay Incoherent Scatter Radar North
Authors: Forsythe Victoriya V. , Makarevich Roman A.
Published: April 2018

Electron density gradients in the polar F region ionosphere are essential for the structuring processes through the gradient‐drift instability (GDI). The information about the typical strength of gradients is important for the theoretical studies and modeling of the GDI waves, but rarely available because of significant experimental challenges in evaluation of the gradients, particularly at small scales and in 3‐D. In this study, multipoint density measurements of the Resolute Bay Incoherent Scatter Radar North working in a special high‐spatial‐resolution mode are employed to address the above question in a systematical manner. The 3‐D gradient vectors as well as their horizontal and vertical components are estimated for the first time and analyzed statistically utilizing a large Resolute Bay Incoherent Scatter Radar North data set. Statistical analysis of the gradient strength shows that the vertical components of the gradient strength vectors are larger than their horizontal counterparts, especially in the lower portion of the F region (below 220 km). The sharpness of the density gradients reveals a significant increase around magnetic midnight due to a decreased effect of the solar smoothing. Further, sharp density gradients occur during magnetically quiet times, possibly because of the presence of the polar holes and reduced plasma precipitation. The peak of occurrence for the horizontal components of the gradient strength vectors occurs at 0.5 × 10−6 m−1, whereas 15.5% of horizontal gradients exceeds 10−5 m−1. These gradients are strong enough for a direct generation of GDI waves at decameter scale (i.e. in linear regime), which implies that nonlinear turbulent cascade is not necessarily required for at least some GDI waves.
Short‐Period Nonlinear Viscoelastic Memory of Rocks Revealed by Copropagating Longitudinal Acoustic Waves
Authors: Feng Xuan , Fehler Michael , Brown Stephen , Szabo Thomas L. , Burns Daniel
Published: April 2018

We describe a new sensitive acoustic method to measure nonlinear viscoelastic properties of rocks directly in the time domain. Unlike static stress‐strain measurements, or dynamic acousto‐elastic methods that use steady state resonance to load a strain field into a rock, our method uses two copropagating longitudinal acoustic waves, one to perturb the strain in the sample and the other to probe the effect of that strain. Experiments on Crab Orchard Sandstone and Lucite samples are presented. We evaluate the time‐dependent nonlinear effects and find strong evidence that rocks have a short‐period nonlinear viscoelastic memory that is a function of the time history of the loaded strain. We develop a phenomenological model to describe both this nonlinear viscoelastic memory and the nonlinear elastic behavior of rock. Our model shows that the viscoelastic memory is controlled by both the traditional nonlinear elastic coefficients and a memory strength parameter. These new observations and methods have significance for quantifying changes in microstructure. This short‐term memory effect, on the order of a small fraction of a cycle, is shown to be related through viscoelasticity to absorption in the sample.
Three‐Dimensional Numerical Modeling of Shear Stimulation of Fractured Reservoirs
Authors: Ucar E. , Berre I. , Keilegavlen E.
Published: April 2018

Shear‐dilation‐based hydraulic stimulations can enable commercial exploitation of geothermal energy from reservoirs with inadequate initial permeability. While contributing to enhancing the reservoir's permeability, hydraulic stimulation processes may also lead to undesired seismic activity. Here we present a three‐dimensional numerical model aiming to aid increased understanding of shear‐dilation based hydraulic stimulation and its consequences. The fractured reservoir is modeled as a network of explicitly represented large‐scale fractures immersed in a permeable rock matrix. The numerical formulation is constructed by coupling three physical processes: fluid flow, fracture deformation, and rock matrix deformation. For flow simulations, the discrete fracture‐matrix model is used, which allows fluid transport from high‐permeable conductive fractures to rock matrix and vice versa. The mechanical behavior of the fractures is modeled with reversible and irreversible deformations corresponding to elastic deformation and slip. Linear elasticity is assumed for mechanical deformation and stress alteration of the rock matrix. Fractures are modeled as lower‐dimensional surfaces embodied in the domain, subjected to specific governing equations for their deformation along the tangential and normal directions. Both the fluid flow and momentum balance equations are approximated by finite volume discretizations. The new numerical model is demonstrated considering a three‐dimensional fractured formation with a network of 20 explicitly represented fractures. The effects of fluid exchange between fractures and rock matrix on the permeability evolution and the generated seismicity are examined for test cases resembling realistic reservoir conditions.
Estimation of Full Moment Tensors, Including Uncertainties, for Nuclear Explosions, Volcanic Events, and Earthquakes
Authors: Alvizuri Celso , Silwal Vipul , Krischer Lion , Tape Carl
Published: April 2018

A seismic moment tensor is a 3 × 3 symmetric matrix that provides a compact representation of a seismic source. We develop an algorithm to estimate moment tensors and their uncertainties from observed seismic data. For a given event, the algorithm performs a grid search over the six‐dimensional space of moment tensors by generating synthetic waveforms for each moment tensor and then evaluating a misfit function between the observed and synthetic waveforms. “The” moment tensor M0 for the event is then the moment tensor with minimum misfit. To describe the uncertainty associated with M0, we first convert the misfit function to a probability function. The uncertainty, or rather the confidence, is then given by the “confidence curve”
, where
is the probability that the true moment tensor for the event lies within a certain neighborhood of M that has fractional volume V. The area under the confidence curve provides a single, abbreviated “confidence parameter” for M0. We apply the method to data from events in different regions and tectonic settings: 17 nuclear explosions and 12 earthquakes at the Nevada Test Site, 63 small (Mw<2.5) events at Uturuncu volcano in Bolivia, and 21 moderate (Mw>4) earthquakes in the southern Alaska subduction zone. Characterization of moment tensor uncertainties puts us in better position to discriminate among moment tensor source types and to assign physical processes to the events.
Does Pacific Variability Influence the Northwest Atlantic Shelf Temperature?
Authors: Chen Ke , Kwon Young‐Oh
Published: April 2018

The relationship between North Pacific variability and sea surface temperature (SST) of the Northwest Atlantic continental shelf is examined over interannual time scale in 1982–2014. Statistically significant negative correlations exist between Pacific Decadal Oscillation (PDO) index and SST in the Gulf of Maine (GoM) in spring and summer. Cross‐correlation analysis further suggests significant negative lead‐lag correlations, with the spring PDO leading the GoM SST by 0–3 months while the summer PDO lags by 1–3 months. These correlations are dominated by the interannual component of the PDO. Statistical relationships are placed in context by further investigating the physical processes controlling the upper ocean mixed layer temperature budget in the GoM. The results reveal contrasting roles between the atmosphere and the ocean in spring and summer, respectively. Local atmospheric forcings, in particular the radiative air‐sea fluxes, are the dominant driver for the interannual variability of springtime SST over the Northwest Atlantic shelf. In contrast, oceanic terms are important in controlling the interannual variability of summertime SST. As a result, reconstructed SST using atmospheric forcings successfully reproduces the statistical relationship with PDO in spring, but not in summer. Furthermore, it is shown that the SST anomalies in the central and eastern North Pacific play a key role in these relationships.
Characteristics of Wave Breaking and Blocking by Spatially Varying Opposing Currents
Authors: Chen Haifei , Zou Qingping
Published: April 2018

A Reynolds‐Averaged Navier‐Stokes (RANS) flow solver with a Volume of Fluid (VOF) surface capturing scheme is used to investigate wave breaking and blocking due to strong opposing currents. The Shear Stress Transport (SST)
model is modified in order to capture the turbulence properly. The unique capability of the RANS‐VOF model allows us to reveal the distinct features of current‐induced wave breaking and blocking. The limiting wave steepness at breaking onset is reduced considerably by the opposing current from the Stokes' limit for stationary waves. Although the wave height grows faster before breaking under a more rapidly varying current, the maximum height at the breaking onset remains almost the same. The locations of incipient breaking are slightly shifted downstream/upwave by the increased current gradient. It was found that the wave radiation stress alters the mean water level by competing with the pressure gradient arising from the current‐induced surface tilting. The wave set‐down and set‐up is more pronounced for more intensive breakers occurring under a larger incident wave and current gradient. Our model results indicate an undertow‐like change to the current profile due to wave breaking. The turbulence and vorticity generated by the current‐induced breaking wave persist and are advected downstream and interact with those generated by the following wave and current.
Scaling Analysis of Multipulsed Turbidity Current Evolution With Application to Turbidite Interpretation
Authors: Ho Viet Luan , Dorrell Robert M. , Keevil Gareth M. , Burns Alan D. , McCaffrey William D.
Published: April 2018

Deposits of submarine turbidity currents, turbidites, commonly exhibit upward‐fining grain size profiles reflecting deposition under waning flow conditions. However, more complex grading patterns such as multiple cycles of inverse‐to‐normal grading are also seen and interpreted as recording deposition under cycles of waxing and waning flow. Such flows are termed multipulsed turbidity currents, and their deposits pulsed or multipulsed turbidites. Pulsing may arise at flow initiation, or following downstream flow combination. Prior work has shown that individual pulses within multipulsed flows are advected forward and merge, such that complex longitudinal velocity profiles eventually become monotonically varying, although transition length scales in natural settings could not be predicted. Here we detail the first high frequency spatial (vertical, streamwise) and temporal measurements of flow velocity and density distribution in multipulsed gravity current experiments. The data support both a process explanation of pulse merging and a phase‐space analysis of transition length scales; in prototype systems, the point of merging corresponds to the transition in any deposit from multipulsed to normally graded turbidites. The scaling analysis is limited to quasi‐horizontal natural settings in which multipulsed flows are generated by sequences of relatively short sediment failures (<10 km long) that develop progressively up‐dip and predicts pulse merging after only a few tens of kilometers. The model cannot provide quantitative estimation of merging in down‐slope flows generated by axially extensive (>10 km) sequences of breaches or where pulsing arises from combination at confluences of single‐pulsed flows, such flows may be responsible for the pulsing signatures seen in some distal turbidites, >100 km from source.
The Role of Oceanic Processes in the Initiation of Indian Summer Monsoon Intraseasonal Oscillations Over the Indian Ocean
Authors: West B. Jason , Han Weiqing , Li Yuanlong
Published: April 2018

Observational analyses and a hierarchy of ocean general circulation model (OGCM) experiments were performed to understand the influence of oceanic processes on the warm sea surface temperature anomalies (SSTAs) prior to the convection initiation of Indian summer monsoon intraseasonal oscillations (MISOs) in the equatorial Indian Ocean. Satellite observations revealed 41 strong MISO events that initiated over the central equatorial Indian Ocean and propagated northward to the Indian subcontinent and/or eastward to the Maritime Continent during the May–October season of the 2001–2012 period. Eight of those events were preceded by SSTAs that were strongly influenced by wind stress‐driven oceanic processes. Composite analyses for the eight events showed that more than one‐third of the preconvection warming in the initiation region resulted from oceanic processes, including advection and entrainment. Case studies of two strong MISO events associated with ocean‐dynamically induced SSTAs showed unmistakable evidence for the preconvection SSTAs and sea surface height anomalies (SSHAs) associated with eastern boundary‐reflected (in June/July 2004) and directly forced (in June 2006) intraseasonal oceanic Rossby waves. In those two case studies, a mixed‐layer heat budget analysis of the OGCM results showed that advection played a much larger role than entrainment in elevating SSTAs. Further analysis showed that intraseasonal currents associated with the Rossby waves advected high seasonal mean SSTs into the initiation region. As current forecasting skills for the onset of the MISO are low, these results underscore the importance of thoroughly understanding the ocean's role in affecting SSTAs, which contribute to MISO initiation.
Curvature‐ and Wind‐Driven Cross‐Channel Flows at an Unstratified Tidal Bend
Authors: Wargula Anna , Raubenheimer Britt , Elgar Steve
Published: April 2018

Observations of currents, water levels, winds, and bathymetry collected for a month at an unstratified, narrow (150 m), shallow (8 m), 90° tidal inlet bend are used to evaluate an analytical model for curvature‐driven flow and the effects of local wind on the cross‐channel circulation. Along‐channel flows ranged from −1.0 to 1.4 m/s (positive is inland), and the magnitudes of cross‐channel flows were roughly 0.1–0.2 m/s near the outer bank of the bend. Cross‐channel observations suggest the lateral sea‐surface gradients and along‐channel flows are tidally asymmetric and spatially variable. The depth‐averaged along‐channel dynamics are consistent with a balance between the surface tilt and centrifugal acceleration. The vertical structure and magnitude of cross‐channel flows during weak winds are consistent with a one‐dimensional depth‐varying balance between centrifugal acceleration, bottom stress, and diffusion. Low‐passed (to remove tides) surface and bottom cross‐channel flows are correlated (r2 = 0.5–0.7) with cross‐channel wind velocity, suggesting that winds can enhance or degrade the local‐curvature‐induced, two‐layer flow and can drive three‐layer flow. The observed flow response to the wind is larger than that expected from a one‐dimensional balance, suggesting that two‐dimensional and three‐dimensional processes may be important.
Decadal‐Scale Riverbed Deformation and Sand Budget of the Last 500 km of the Mississippi River: Insights Into Natural and River Engineering Effects on a Large Alluvial River
Authors: Wang Bo , Xu Y. Jun
Published: April 2018

Alluvial rivers are shaped by interactions of flow and sediment transport. Their lower reaches to the world's oceans are highly dynamic, often presenting engineering and management challenges. Here we analyzed over 6,000 single‐beam cross‐sectional measurements surveyed in 1992, 2004, and 2013 in the last 500‐km reach of the highly engineered Mississippi River, also known as the lowermost Mississippi River or LmMR, starting from the river's Gulf outlet to its avulsion into the Atchafalaya River. We applied inverse distance weighted interpolation to downscale the survey records into 10 × 10 m digital elevation models. We assessed riverbed deformation from bank to bank and quantified changes in riverbed sediment volume. The goal of our study is to test the hypothesis that the lower reach of a large alluvial river can function as a conduit for sediment transport under the current engineering focus of navigation safety and flood control. Our analysis shows that in the past two decades, nearly 70% of the riverine sand was trapped within the LmMR, and continuous riverbed aggradation occurred below the Mississippi‐Atchafalaya diversion, presenting favorable backwater conditions for avulsion. Backwater effects have mainly controlled riverbed deformation in the LmMR, while flow reduction may have also contributed to the channel aggradation in the uppermost and lowermost reaches. The study reveals the considerable complexity of geomorphic responses of a large alluvial river to human interventions, strongly suggesting that future river engineering and management of the world's alluvial rivers should focus on strategies and solutions that will improve sediment transport.
An Improved Algorithm for Unmixing First‐Order Reversal Curve Diagrams Using Principal Component Analysis
Authors: Harrison Richard J. , Muraszko Joy , Heslop David , Lascu Ioan , Muxworthy Adrian R. , Roberts Andrew P.
Published: April 2018

First‐order reversal curve (FORC) diagrams of synthetic binary mixtures with single‐domain, vortex state, and multidomain end‐members (EMs) were analyzed using principal component analysis (FORC‐PCA). Mixing proportions derived from FORC‐PCA are shown to deviate systematically from the known weight percent of EMs, which is caused by the lack of reversible magnetization contributions to the FORC distribution. The error in the mixing proportions can be corrected by applying PCA to the raw FORCs, rather than to the processed FORC diagram, thereby capturing both reversible and irreversible contributions to the signal. Here we develop a new practical implementation of the FORC‐PCA method that enables quantitative unmixing to be performed routinely on suites of FORC diagrams with up to four distinct EMs. The method provides access not only to the processed FORC diagram of each EM, but also to reconstructed FORCs, which enables objective criteria to be defined that aid identification of physically realistic EMs. We illustrate FORC‐PCA with examples of quantitative unmixing of magnetic components that will have widespread applicability in paleomagnetism and environmental magnetism.
Interfacial Form Stress in the Southern Ocean State Estimate
Authors: Masich Jessica , Mazloff Matthew R. , Chereskin Teresa K.
Published: April 2018

The wind stress that drives the Antarctic Circumpolar Current (ACC) exits the fluid via topographic form stress (TFS) at the sea floor; interfacial form stress (IFS) is thought to carry much of this momentum from source to sink. These form stresses combine to help set the strength and structure of the Southern Ocean meridional overturning circulation (MOC), a key nexus of heat and gas exchange between the deep ocean and the atmosphere. For the first time in a general circulation model, we calculate the time‐varying, three‐dimensional IFS field directly from zonal pressure gradients across vertical perturbations in isopycnal layer interfaces. We confirm previous findings that IFS compensates wind stress at the surface and topographic form stress at the seafloor in the Drake Passage latitudes. We find that zonal and time‐mean IFS is primarily responsible for this surface wind stress compensation, with some contribution from transient eddy IFS. Mean, standing eddy, and transient eddy IFS combine to compensate topographic form stress at depth. Both standing and transient eddy IFS concentrate at stationary meanders along the ACC, and transient eddy IFS dominates standing eddy IFS in regions of high eddy kinetic energy. Finally, total IFS changes sign from balancing eastward wind stress to balancing westward topographic form stress around 28.1 kg m−3, close to the upper limit of Antarctic Bottom Water, indicating the role of buoyancy forcing in setting the structure of the IFS field.
Coherent Circulation Changes in the Deep North Atlantic From 16°N and 26°N Transport Arrays
Authors: Frajka‐Williams E. , Lankhorst M. , Koelling J. , Send U.
Published: April 2018

The meridional overturning circulation (MOC) has been measured by boundary arrays in the Atlantic since 2000. Over the past decade of measurements, however, the reported tendencies in overturning circulation strength have differed between 16°N and 26°N. Here we investigate these differences by diagnosing their origin in the observed hydrography, finding that both arrays show deep waters (below 1,100 dbar) at the western boundary becoming fresher and less dense. The associated change in geopotential thickness is about 0.15 m2 s−2 between 2004–2009 and 2010–2014, with the shift occurring between 2009 and 2010 and earlier at 26°N than 16°N. In the absence of a similar density change on the east of the Atlantic, this middepth reduction in water density at the west would drive an increase in the shear between the upper and lower layers of North Atlantic Deep Water of about 2.6 Sv at 26°N and 3.9 Sv at 16°N. These transport anomalies result in an intensifying tendency in the MOC estimate at 16°N, but at 26°N, the method of correcting the geostrophic reference level results in an opposing (reducing) tendency of the MOC. The results indicate that both arrays are observing coherent, low‐frequency changes, but that there remain discrepancies in the methods of addressing the geostrophic reference level for boundary arrays measuring ocean circulation.
Groundwater Isotopes Biased Toward Heavy Rainfall Events and Implications on the Local Meteoric Water Line
Authors: Li Jie , Pang Zhonghe , Kong Yanlong , Wang Shufang , Bai Guoying , Zhao Hongyi , Zhou Dong , Sun Feng , Yang Zhongshan
Published: April 2018

Stable water isotopes are useful tracers in the groundwater recharge studies, where the local meteoric water line (LMWL) usually serves as a reference line and the amount‐weighted average value of precipitation is regarded as the input meteoric signal. Based on a comparison of isotope composition between precipitation and groundwater collected from a groundwater basin in the Beijing area, we verify that small precipitation events do not constitute effective groundwater recharge in a (semi) arid region, causing that the isotopes in groundwater are biased toward the meteoric isotopic signal of heavy rainfall events. The positive deflections in groundwater levels from a phreatic aquifer in Yanqing Basin in the Northwest of Beijing revealed that recharge occurs exclusively during the rainy seasons and is clearly associated with heavy rainfall events (>10 mm/day). The isotope composition of groundwater samples that plot far below the mean meteoric input value, further strengthen the dependence of groundwater recharge on heavy rainfall events. We construct the LMWLs with different regression methods using daily stable isotope data from seven hydro‐meteorological stations over a hydrological year. When the δ18O ranges from −20‰ to 10‰, the lines are quite similar regressed by the weighted monthly values and by heavy rainfall events, so the conventional LMWL can still serve as the reference line for groundwater recharge studies.
Learning About Planets Through Studying Wind‐Related Processes on Earth
Authors: Zimbelman James R. , Tsoar Haim
Published: April 2018

The Planetary Geology Field Conference on Aeolian Processes was held in Southern California on 10–14 January 1978. This meeting brought researchers involved in the study of wind‐related landforms on Mars together with experts in field and laboratory studies of aeolian features on Earth. This seminal field conference established a pattern that has recently been continued through a series of International Planetary Dunes Workshops.
Yes-associated protein (YAP) in pancreatic cancer: at the epicenter of a targetable signaling network associated with patient survival
Authors: Rozengurt Enrique , Sinnett-Smith James , Eibl Guido
Published: April 2018

Pancreatic ductal adenocarcinoma (PDAC) is generally a fatal disease with no efficacious treatment modalities. Elucidation of signaling mechanisms that will lead to the identification of novel targets for therapy and chemoprevention is urgently needed. Here, we review the role of Yes-associated protein (YAP) and WW-domain-containing Transcriptional co-Activator with a PDZ-binding motif (TAZ) in the development of PDAC. These oncogenic proteins are at the center of a signaling network that involves multiple upstream signals and downstream YAP-regulated genes. We also discuss the clinical significance of the YAP signaling network in PDAC using a recently published interactive open-access database (www.proteinatlas.org/pathology) that allows genome-wide exploration of the impact of individual proteins on survival outcomes. Multiple YAP/TEAD-regulated genes, including AJUBA, ANLN, AREG, ARHGAP29, AURKA, BUB1, CCND1, CDK6, CXCL5, EDN2, DKK1, FOSL1,FOXM1, HBEGF, IGFBP2, JAG1, NOTCH2, RHAMM, RRM2, SERP1, and ZWILCH, are associated with unfavorable survival of PDAC patients. Similarly, components of AP-1 that synergize with YAP (FOSL1), growth factors (TGFα, EPEG, and HBEGF), a specific integrin (ITGA2), heptahelical receptors (P2Y
2
R, GPR87) and an inhibitor of the Hippo pathway (MUC1), all of which stimulate YAP activity, are associated with unfavorable survival of PDAC patients. By contrast, YAP inhibitory pathways (STRAD/LKB-1/AMPK, PKA/LATS, and TSC/mTORC1) indicate a favorable prognosis. These associations emphasize that the YAP signaling network correlates with poor survival of pancreatic cancer patients. We conclude that the YAP pathway is a major determinant of clinical aggressiveness in PDAC patients and a target for therapeutic and preventive strategies in this disease.
Ube2s stabilizes β-Catenin through K11-linked polyubiquitination to promote mesendoderm specification and colorectal cancer development
Authors: Li Zhaoyan , Wang Yan , Li Yadan , Yin Wanqi , Mo Libin , Qian Xianghao , Zhang Yiran , Wang Guifen , Bu Fan , Zhang Zhiling , Ren Xiaofang , Zhu Baochang , Niu Chang , Xiao Wei , Zhang Weiwei
Published: April 2018

The canonical Wnt/β-Catenin signaling pathway is widely involved in regulating diverse biological processes. Dysregulation of the pathway results in severe consequences, such as developmental defects and malignant cancers. Here, we identified Ube2s as a novel activator of the Wnt/β-Catenin signaling pathway. It modified β-Catenin at K19 via K11-linked polyubiquitin chain. This modification resulted in an antagonistic effect against the destruction complex/β-TrCP cascade-orchestrated β-Catenin degradation. As a result, the stability of β-Catenin was enhanced, thus promoting its cellular accumulation. Importantly, Ube2s-promoted β-Catenin accumulation partially released the dependence on exogenous molecules for the process of embryonic stem (ES) cell differentiation into mesoendoderm lineages. Moreover, we demonstrated that UBE2S plays a critical role in determining the malignancy properties of human colorectal cancer (CRC) cells in vitro and in vivo. The findings in this study extend our mechanistic understanding of the mesoendodermal cell fate commitment, and provide UBE2S as a putative target for human CRC therapy.
Identification of somatic mutations in monozygotic twins discordant for psychiatric disorders
Authors: Nishioka Masaki , Bundo Miki , Ueda Junko , Yoshikawa Akane , Nishimura Fumichika , Sasaki Tsukasa , Kakiuchi Chihiro , Kasai Kiyoto , Kato Tadafumi , Iwamoto Kazuya
Published: April 2018

Monozygotic twins are assumed to have identical genomes. Based on this assumption, phenotypic discordance in monozygotic twins has been previously attributed to environmental factors. However, recent genomic studies have identified characteristic somatic mutations in monozygotic twins discordant for Darier disease, Van der Woude syndrome, and Dravet syndrome. Here, we explored somatic mutations in four pairs of monozygotic twins discordant for schizophrenia or delusional disorder. We analyzed whole exome sequence data obtained from blood samples and identified seven somatic mutations in one twin pair discordant for delusional disorder. All seven of these mutations were validated by independent amplicon sequencing, and five of them were further validated by pyrosequencing. One somatic mutation in the patient with delusional disorder showed a missense variant in ABCC9 with an allele fraction of 7.32%. Although an association between the somatic mutations and phenotypic discordance could not be established conclusively in this study, our results suggest that somatic mutations in monozygotic twins may contribute to the development of psychiatric disorders, and can serve as high-priority candidates for genetic studies.
Effect of bovine milk fat globule membranes as a complementary food on the serum metabolome and immune markers of 6-11-month-old Peruvian infants
Authors: Lee Hanna , Zavaleta Nelly , Chen Shin-Yu , Lönnerdal Bo , Slupsky Carolyn
Published: April 2018

This study builds on a previous study by this group in which 6–11-month-old Peruvian infants who were fed bovine milk fat globule membrane (MFGM) containing complementary food had significantly fewer episodes of infection-related bloody diarrhea relative to those consuming a control food (skim milk powder). Micronutrient deficiencies including zinc deficiency were prevalent in this study population. To understand the mechanism behind the health benefits of consuming MFGM, the serum metabolome and cytokine levels, as markers for systemic immune responses, were evaluated using 1H nuclear magnetic resonance-based metabolomics and a multiplex system, respectively. Combined with data on micronutrient status and anthropometry, a comparative analysis was performed. Supplementation with MFGM tended to improve micronutrient status, energy metabolism, and growth reflected as increased levels of circulating amino acids and weight gain, particularly in female infants compared to controls. Decreased levels of the microbial choline metabolite trimethylamine-N-oxide in the MFGM-supplemented group (both male and female infants) suggest a functional perturbation in the intestinal microbiota. A cytokine shift toward a less T helper type 1 response was observed in those receiving the MFGM supplement, which was mainly attributed to decreases in interleukin-2 levels. Our findings suggest that consumption of MFGM with complementary food may reverse the metabolic abnormalities found in marginally nourished infants, thereby improving metabolic regulation, which may lead to enhanced immunity.
Direct evidence for α ether linkage between lignin and carbohydrates in wood cell walls
Authors: Nishimura Hiroshi , Kamiya Akihiro , Nagata Takashi , Katahira Masato , Watanabe Takashi
Published: April 2018

Cross-linking between lignin and polysaccharide in plant cell-wall determines physical, chemical, and biological features of lignocellulosic biomass. Since Erdmann’s first report in 1866, numerous studies have suggested the presence of a bond between hemicelluloses and lignin; however, no clear evidence for this interaction has been reported. We describe the first direct proof of covalent bonding between plant cell-wall polysaccharides and lignin. Nuclear magnetic resonance spectroscopy was used to observe the long-range correlations through an α-ether bond between lignin and the primary hydroxyl group of a mannose residue in glucomannan. Complete signal assignment of the cognate structural units was also achieved. Thus, we identified lignin–carbohydrate bonds by complete connectivity analysis from the phenylpropane unit to the carbohydrate moiety.
Leukocyte telomere length and diet in the apparently healthy, middle-aged Asklepios population
Authors: De Meyer Tim , Bekaert Sofie , De Buyzere Marc L. , De Bacquer Dirk D. , Langlois Michel R. , Shivappa Nitin , Hébert James R. , Gillebert Thierry C. , Rietzschel Ernst R. , Huybrechts Inge
Published: April 2018

Telomere length is a prognostic biomarker for aging diseases. As it is unknown whether diet plays a role in these associations, we aimed to assess the impact of diet on telomere length. Moreover, given that telomere length is modulated by oxidative stress and inflammation, an additional goal was to evaluate whether the latter may mediate possible telomere – diet associations. Southern blot measured leukocyte telomere length and food frequency questionnaire data were compared for 2509 apparently healthy men and women (~35 to 55 years) from the Asklepios population. No significant associations were found between telomere length and overall dietary characteristics, such as dietary diversity, quality, equilibrium, and the dietary inflammatory index. Exploratory analysis of individual dietary variables revealed that a higher daily intake of deep fried potato products was associated with shorter telomeres (P = 0.002, 151 bp per 100 g/day), also in both sexes separately. Deep fried potato product consumption was also significantly associated with C-reactive protein (P = 0.032) and uric acid (P = 0.042), but not other inflammation and oxidative stress markers. These results suggest an at most limited association between overall dietary patterns and telomere length in the general population. Nevertheless, the association between telomere length and deep fried potato product intake warrants additional research.
Predictability of Arctic sea ice on weather time scales
Authors: Mohammadi-Aragh M. , Goessling H. F. , Losch M. , Hutter N. , Jung T.
Published: April 2018

The field of Arctic sea ice prediction on “weather time scales” is still in its infancy with little existing understanding of the limits of predictability. This is especially true for sea ice deformation along so-called Linear Kinematic Features (LKFs) including leads that are relevant for marine operations. Here the potential predictability of the sea ice pack in the wintertime Arctic up to ten days ahead is determined, exploiting the fact that sea ice-ocean models start to show skill at representing sea ice deformation at high spatial resolutions. Results are based on ensemble simulations with a high-resolution sea ice-ocean model driven by atmospheric ensemble forecasts. The predictability of LKFs as measured by different metrics drops quickly, with predictability being almost completely lost after 4–8 days. In contrast, quantities such as sea ice concentration or the location of the ice edge retain high levels of predictability throughout the full 10-day forecast period. It is argued that the rapid error growth for LKFs is mainly due to the chaotic behaviour of the atmosphere associated with the low predictability of near surface wind divergence and vorticity; initial condition uncertainty for ice thickness is found to be of minor importance as long as LKFs are initialized at the right locations.
Dynamic Metasurface Aperture as Smart Around-the-Corner Motion Detector
Authors: del Hougne Philipp , F. Imani Mohammadreza , Sleasman Timothy , Gollub Jonah N. , Fink Mathias , Lerosey Geoffroy , Smith David R.
Published: April 2018

Detecting and analysing motion is a key feature ofSmart Homesand the connected sensor vision they embrace. At present, most motion sensors operate in line-of-sight Doppler shift schemes. Here, we propose an alternative approach suitable for indoor environments, which effectively constitute disordered cavities for radio frequency (RF) waves; we exploit the fundamental sensitivity of modes of such cavities to perturbations, caused here by moving objects. We establish experimentally three key features of our proposed system: (i) ability to capture the temporal variations of motion and discern information such as periodicity (“smart”), (ii) non line-of-sight motion detection, and (iii) single-frequency operation. Moreover, we explain theoretically and demonstrate experimentally that the use of dynamic metasurface apertures can substantially enhance the performance of RF motion detection. Potential applications include accurately detecting human presence and monitoring inhabitants’ vital signs.
Dirac cone intensity asymmetry and surface magnetic field in V-doped and pristine topological insulators generated by synchrotron and laser radiation
Authors: Shikin A. M. , Rybkina A. A. , Estyunin D. A. , Sostina D. M. , Klimovskikh I. I. , Voroshnin V. Yu. , Rybkin A. G. , Kokh K. A. , Tereshchenko O. E. , Petaccia L. , Di Santo G. , Kimura A. , Skirdkov P. N. , Zvezdin K. A. , Zvezdin A. K.
Published: April 2018

Effect of magnetization generated by synchrotron or laser radiation in magnetically-doped and pristine topological insulators (TIs) is presented and analyzed using angle-resolved photoemission spectroscopy. It was found that non-equal photoexcitation of the Dirac cone (DC) states with opposite momenta and spin orientation indicated by the asymmetry in photoemission intensity of the DC states is accompanied by the k||-shift of the DC states relative to the non-spin-polarized conduction band states located at k|| = 0. We relate the observed k||-shift to the induced surface in-plane magnetic field and corresponding magnetization due to the spin accumulation. The direction of the DC k||-shift and its value are changed with photon energy in correlation with variation of the sign and magnitude of the DC states intensity asymmetry. The theoretical estimations describe well the effect and predict the DC k||-shift values which corroborate the experimental observations. This finding opens new perspectives for effective local magnetization manipulation.
Development of a 3D seed morphological tool for grapevine variety identification, and its comparison with SSR analysis
Authors: Karasik Avshalom , Rahimi Oshrit , David Michal , Weiss Ehud , Drori Elyashiv
Published: April 2018

Grapevine (Vitis vinifera L.) is one of the classical fruits of the Old World. Among the thousands of domesticated grapevine varieties and variable wild sylvestris populations, the range of variation in pip morphology is very wide. In this study we scanned representative samples of grape pip populations, in an attempt to probe the possibility of using the 3D tool for grape variety identification. The scanning was followed by mathematical and statistical analysis using innovative algorithms from the field of computer sciences. Using selected Fourier coefficients, a very clear separation was obtained between most of the varieties, with only very few overlaps. These results show that this method enables the separation between different Vitis vinifera varieties. Interestingly, when using the 3D approach to analyze couples of varieties, considered synonyms by the standard 22 SSR analysis approach, we found that the varieties in two of the considered synonym couples were clearly separated by the morphological analysis. This work, therefore, suggests a new systematic tool for high resolution variety discrimination.
MALAT1: An Epigenetic Regulator of Inflammation in Diabetic Retinopathy
Authors: Biswas Saumik , Thomas Anu Alice , Chen Shali , Aref-Eshghi Erfan , Feng Biao , Gonder John , Sadikovic Bekim , Chakrabarti Subrata
Published: April 2018

Despite possessing limited protein-coding potential, long non-coding RNAs (lncRNAs) have been implicated in a myriad of pathologic conditions. Most well documented in cancer, one prominent intergenic lncRNA known as MALAT1 is notorious for its role in impacting epigenetic mechanisms. In this study, we established a novel epigenetic paradigm for MALAT in diabetic retinopathy (DR) by employing siRNA-mediated MALAT1 knockdown in human retinal endothelial cells (HRECs), a Malat1 knockout animal model, vitreous humor from diabetic patients, pharmacological inhibitors for histone and DNA methylation, RNA immunoprecipitation, western blotting, and a unique DNA methylation array to determine glucose-related alterations in MALAT1. Our findings indicated that MALAT1 is capable of impacting the expressions of inflammatory transcripts through its association with components of the PRC2 complex in diabetes. Furthermore, the vitreous humors from diabetic patients revealed increased expressions of MALAT1, TNF-α, and IL-6. Intriguingly, our DNA methylation array demonstrated that transient high glucose exposure in HRECs does not contribute to significant methylation alterations at CpG sites across the MALAT1 gene. However, global inhibition of DNA methyltransferases induced significant increases in MALAT1 and associated inflammatory transcripts in HRECs. Our findings collectively demonstrate the importance of MALAT1 in inflammation and epigenetic regulation in DR.