bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro and In Vivo Evaluation of Targeted Sunitinib‐Loaded Polymer Microbubbles Against Proliferation of Renal Cell Carcinoma
Authors: Hu Jie , Zong Yujin , Li Jun , Zhou Xiaodong , Zhang Jun , Zhu Ting , Jiao Mingke , Su Haili , Bo Bin
Published: February 2016

Objectives

The poor safety profile of sunitinib capsules has encouraged the identification of targeted drug delivery systems against renal cell carcinoma. This study aimed to explore the effect of sunitinib‐loaded microbubbles along with ultrasound (US) treatment on proliferation and apoptosis of human GRC‐1 granulocyte renal carcinoma cells in vitro and in vivo (xenograft tumor growth in nude mice).

Methods

Liposomes containing sunitinib were prepared by using the transmembrane ammonium sulfate gradient method and then absorbed into polymer microbubbles to generate sunitinib‐loaded microbubbles. Entrapment of sunitinib was verified by 25‐25‐[N‐[(7‐nitro‐2‐1,3‐benzoxadiazol‐4‐yl)methyl]amino]‐27‐norcholesterol staining. GRC‐1 cells were treated with microbubbles alone, liposomes alone, sunitinib alone, sunitinib‐loaded microbubbles without and with US, and no treatment (control). Cell survival and apoptosis were assessed at 12, 24, and 48 hours after treatment. Xenograft tumors were induced by implantation of GRC‐1 cells in nude mice. The animals with tumors were then randomly assigned to sunitinib alone, sunitinib‐loaded microbubbles − US, sunitinib‐loaded microbubbles + US, and no treatment (control; n = 10 per group). The tumor volumes were analyzed on the 7th, 15th, and 21st days.

Results

The sunitinib entrapment efficiency in the liposomes was approximately 78%. The effective sunitinib concentration in each group was 0.1 μg/mL. The sunitinib‐loaded microbubble + US group showed a lower in vitro cell survival rate (P < .001) compared with the other groups. Greater in vivo inhibition of xenograft tumor growth was also observed in the sunitinib‐loaded microbubble + US group compared with the other groups.

Conclusions

Combined sunitinib‐loaded microbubbles and US treatment significantly inhibits growth of renal carcinoma cells both in vitro and in vivo.
Obstetric Ultrasound Efficiency and Accuracy Using a Protocol‐Based Examination
Authors: Ruma Michael S. , Bradley Heather , Holstrom Anna , Rigdon Joseph , Herring Amy
Published: February 2016

Objectives

Obstetric ultrasound imaging requires the acquisition of a standard set of maternal and fetal images. Our objective was to evaluate the impact of implementation of a protocol‐based ultrasound examination on the duration of ultrasound examinations, examination completion, and accuracy of documentation.

Methods

We conducted a case‐cohort study. Obstetric ultrasound examinations performed in the first, second, and third trimesters were reviewed before and after implementation of a protocol‐based ultrasound examination. The duration of the ultrasound examination, number of missing required images, and documentation of missing images were abstracted from an image archival system. To account for clustering by sonographer, 3 mixed effects models with a fixed effect for protocol and a random intercept for sonographer were used to evaluate the effect on the total time of the examination, number of missing images, and whether missing images were documented.

Results

A total of 100 ultrasound examinations were compared: 50 before and 50 after implementation of the protocol. Statistically significant differences between outcomes before and after protocol implementation were observed for all outcomes. After implementation of the protocol, the average duration of ultrasound examinations decreased by 7.62 minutes (95% confidence interval [CI], 3.57–11.68 minutes); the number of missing images was reduced by 5.81 per examination (95% CI, 4.24–7.39); and proper documentation of missing images increased by 40.24% (95% CI, 22.77%–57.71%).

Conclusions

Implementation of a software protocol–based ultrasound examination significantly improved the efficiency and accuracy of obstetric ultrasound examinations in this study.
Superficial Echogenic Lesions Detected on Neonatal Cranial Sonography
Authors: Han Byoung Hee , Song Mi Jin , Lee Kyung Sang , Kim Young-Hwa , Ko Sun Young , Jung Goun , Park Sung Bin , Lee Seung-Koo
Published: February 2016

Objectives

The purpose of this study was to evaluate the characteristics and importance of superficial echogenic lesions around cranial sutures on neonatal cranial sonography.

Methods

We retrospectively reviewed the clinical records and neuroimaging studies of 40 neonates who had superficial echogenic lesions around sutures on neonatal cranial sonography. Magnetic resonance imaging (n = 18) and computed tomography (n = 2) were performed within 2 weeks after sonography. We correlated sonographic findings with computed tomographic and magnetic resonance imaging findings and analyzed them. We also evaluated the associated lesions, neurologic signs, and follow‐up changes.

Results

Sonographically, the superficial echogenic lesions involved both sulci and perisulcal parenchyma in 39 neonates and were located in the frontal and parietal areas around the sagittal suture in 38 neonates. Magnetic resonance imaging revealed a pattern of hypoxic ischemic encephalopathy in 9 neonates, birth trauma in 3 neonates, a mixed pattern of hypoxic ischemic encephalopathy and trauma in 3 neonates, nonspecific single infarctions in 2 neonates, and lack of a defined lesion in 1 neonate. The associated lesions were subdural hemorrhage (n = 12), epidural hematoma (n = 4), germinal matrix hemorrhage (n = 3), intraventricular hemorrhage (n = 2), and periventricular leukomalacia (n = 1). All epidural hematomas were associated with scalp hematoma, and 2 patients had skull fractures. One neonate with epidural hematoma associated with a hypoxic ischemic encephalopathy pattern showed mild spasticity in both ankles until 16 months.

Conclusions

Superficial echogenic lesions detected around cranial sutures on neonatal sonography may be an indicator of more serious intracranial lesions such as more extensive hypoxic ischemic encephalopathy and intracranial hematomas, including epidural hematoma.
Prenatal Visualization of the Pulmonary and Aortic Valves and Leaflets Is Feasible Using 4‐Dimensional Sonography
Authors: Adriaanse Bauke M. E. , Uittenbogaard Lukas B. , Tromp Chantal H. N. , Heymans Martijn W. , van Vugt John M. G. , Haak Monique C.
Published: February 2016

Objectives

The purpose of this study was to determine whether the morphologic characteristics and area of the semilunar valves in healthy fetuses and fetuses with cardiac defects can be visualized by using spatiotemporal image correlation (STIC).

Methods

Spatiotemporal image correlation volumes from 74 healthy fetuses were recorded in 5 examinations between the 15th and 36th weeks of pregnancy. Second, we recorded STIC volumes from 64 fetuses with various cardiac defects. The quality of the volumes was rated. The areas of the aortic and pulmonary valves were measured in systole by rendering the valves on 4‐dimensional sonography. The number of leaflets was examined. Longitudinal data analysis using linear mixed models was performed.

Results

Two hundred ninety‐three volumes from normal hearts were examined. In 82.5%, the quality of the normal volumes was sufficient. Visualization of the valve opening was feasible in 96.1% of the normal hearts and 97.4% of the abnormal hearts. The success rate of visualization of the pulmonary and aortic valve leaflets was dependent on the gestational age, with the highest percentage (72.1% in normal hearts) at 19 to 24 weeks. Longitudinal regression analysis showed a positive relationship of the aortic and pulmonary valve areas with gestational age (P < .0001) and fetal biometric measurements (P < .0001). Fifty‐eight abnormal volumes were examined. Cardiac defects with abnormal valve areas due to aortic and pulmonary stenosis could be clearly visualized by using STIC.

Conclusions

Examination of the morphologic characteristics of the semilunar valves using STIC is feasible, which is difficult when using 2‐dimensional sonography. With increasing implementation of 4‐dimensional sonography, the understanding of rendered images might be useful for anyone practicing fetal echocardiography.
Three‐Dimensional Sonography of Axillary Lymph Nodes in Patients With Breast Cancer
Authors: Koenigsberg Tova C. , Reig Beatriu , Frank Susan
Published: February 2016

Sonography is useful in the evaluation of axillary lymph nodes in patients with breast cancer. In this pictorial essay, we review the range of grayscale and Doppler appearances of abnormal axillary lymph nodes on 2‐dimensional and 3‐dimensional imaging.
Clinical Importance and Natural History of Biliary Sludge in Outpatients
Authors: Hill Paul Armstrong , Harris Robert D.
Published: February 2016

Objectives

Gallbladder sludge is a common diagnosis on routine abdominal sonography, yet its clinical importance is uncertain, especially in outpatients. To determine its natural history and potential future complications in this setting, we reviewed the imaging and clinical histories of nonhospitalized patients with a diagnosis of sludge on sonography.

Methods

We conducted a retrospective search of our institutional radiology information system for all sonographic reports using the key words “biliary sludge without gallstones” over a 3‐year period. For each of the 104 patients with isolated biliary sludge on initial sonography, we reviewed the electronic medical records and all imaging for the development of pancreaticobiliary complications.

Results

We found an overall prevalence of biliary sludge in outpatients of 1.8%. Of the 104 patients reviewed with a mean follow up of 630 days (21 months), 25 developed a pancreaticobiliary complication, including cholelithiasis, cholecystitis, choledocholithiasis, and pancreatitis. The most frequent complication was cholecystitis, with a total of 14 diagnoses (12 chronic acalculous and 2 acute with gallstones). An additional 6 patients developed gallstones without cholecystitis features; 4 patients developed pancreatitis; and 1 developed choledocholithiasis. Biliary sludge remained quiescent or resolved in 76% of patients.

Conclusions

Biliary sludge always represents a pathologic process, but its clinical implications among outpatients have not been previously investigated. Our ambulatory population developed pancreaticobiliary complications at similar rates as prior mixed–patient setting studies. Regardless of the patient setting, biliary sludge is likely of more clinical importance than previously regarded.
Atypical Presentations of Molar Pregnancy
Authors: Mohamed Sara A. , Al-Hendy Ayman , Ghamande Sharad , Chaffin Joanna , Browne Paul
Published: February 2016

In modern practice, the diagnosis of molar pregnancy is made at an early gestational age. The opportunity to diagnose gestational trophoblastic disease (GTD) using sonography alone occurs less frequently. The classic appearance of a “snowstorm” in the endometrial cavity and bilateral theca lutein cysts still applies to the diagnosis of second‐trimester GTD. The diagnosis of first‐trimester GTD requires increased clinical suspicion. If the sonographic appearance of the pregnancy is atypical, GTD should be included in the differential diagnosis. Additional nonimaging criteria such as serial quantitative β‐human chorionic gonadotropin levels, pathologic examination, and p57 (cyclin‐dependent kinase inhibitor 1C protein) immunostaining can accurately confirm the diagnosis of GTD.
Evanescent Hyperechoic Changes After Fine‐Needle Aspiration Biopsy of the Thyroid in a Series With a Low Overall Prevalence of Complications
Authors: Uchida Toyoyoshi , Himuro Miwa , Komiya Koji , Goto Hiromasa , Takeno Kageumi , Honda Akira , Sato Junko , Kawano Yui , Suzuki Ruriko , Watada Hirotaka
Published: February 2016

Objectives

The purpose of this study was to assess the frequency of and risk factors for fine‐needle aspiration biopsy (FNAB)‐related complications in Japanese patients with thyroid nodules evaluated by standard FNAB techniques.

Methods

Six hundred fifty‐three consecutive Japanese patients with 742 nodules who had undergone FNAB were enrolled. Nodule characteristics were evaluated, and thyroid volumes were measured. Fine‐needle aspiration biopsy–related complications were identified on the basis of sonographic findings and patients’ conditions after undergoing FNAB. Comparisons of patients’ backgrounds and nodule characteristics were made between those with and without complications.

Results

The prevalence rates for FNAB‐related complications, including acute transient thyroid swelling after FNAB and appearance of anechoic lesions, were 0.13% and 0.94%. In this study, we could not identify risk factors for FNAB‐related complications. The sudden appearance of bright hyperechoic foci within the thyroid immediately after biopsy was reported as an FNAB‐related unfamiliar appearance in 5 cases. Experimental FNA using resected porcine thyroid tissue suggested that the etiology of the hyperechoic appearance may be artificial air bubbles or reversed flow of aspirated fluid.

Conclusions

Fine‐needle aspiration biopsy–related complications are rare if preventive measures are performed and are not specific to Japanese patients with thyroid nodules. The sudden appearance of bright hyperechoic foci may be cause by contamination from air or fluid.
Evaluation of downscaled, gridded climate data for the conterminous United States
Authors: Behnke R. , Vavrus S. , Allstadt A. , Albright T. , Thogmartin W. E. , Radeloff V. C.
Published: February 2016

Weather and climate affect many ecological processes, making spatially continuous yet fine‐resolution weather data desirable for ecological research and predictions. Numerous downscaled weather data sets exist, but little attempt has been made to evaluate them systematically. Here we address this shortcoming by focusing on four major questions: (1) How accurate are downscaled, gridded climate data sets in terms of temperature and precipitation estimates? (2) Are there significant regional differences in accuracy among data sets? (3) How accurate are their mean values compared with extremes? (4) Does their accuracy depend on spatial resolution? We compared eight widely used downscaled data sets that provide gridded daily weather data for recent decades across the United States. We found considerable differences among data sets and between downscaled and weather station data. Temperature is represented more accurately than precipitation, and climate averages are more accurate than weather extremes. The data set exhibiting the best agreement with station data varies among ecoregions. Surprisingly, the accuracy of the data sets does not depend on spatial resolution. Although some inherent differences among data sets and weather station data are to be expected, our findings highlight how much different interpolation methods affect downscaled weather data, even for local comparisons with nearby weather stations located inside a grid cell. More broadly, our results highlight the need for careful consideration among different available data sets in terms of which variables they describe best, where they perform best, and their resolution, when selecting a downscaled weather data set for a given ecological application.
Crystal structure of Thermoplasma acidophilum XerA recombinase shows large C‐shape clamp conformation and cis‐cleavage mode for nucleophilic tyrosine
Authors: Jo Chang Hwa , Kim Junsoo , Han Ah‐reum , Park Sam Yong , Hwang Kwang Yeon , Nam Ki Hyun
Published: February 2016

Site‐specific Xer recombination plays a pivotal role in reshuffling genetic information. Here, we report the 2.5 Å crystal structure of XerA from the archaean Thermoplasma acidophilum. Crystallographic data reveal a uniquely open conformational state, resulting in a C‐shaped clamp with an angle of ~ 48° and a distance of 57 Å between the core‐binding and the catalytic domains. The catalytic nucleophile, Tyr264, is positioned in cis‐cleavage mode by XerA's C‐term tail that interacts with the CAT domain of a neighboring monomer without DNA substrate. Structural comparisons of tyrosine recombinases elucidate the dynamics of Xer recombinase.
Structural basis for a novel interaction between TXNIP and Vav2
Authors: Liu Shasha , Wu Xue , Zong Minru , Tempel Wolfram , Loppnau Peter , Liu Yanli
Published: February 2016

Thioredoxin‐interacting protein (TXNIP) is a multifunctional protein involved in diverse cellular processes such as cell proliferation and apoptosis. TXNIP stability is controlled by the ubiquitin–proteasome pathway, and the E3 ubiquitin ligase Itch directly interacts with TXNIP via PPxY motifs of TXNIP. In a previously published study, we have shown that phosphorylation of the PPxY tyrosyl residue switches TXNIP selectivity between different binding partners. Here, we describe that tyrosine‐phosphorylated PPxY motifs also bind to SH2 domains of Vav2 and Src with dissociation constants around 10 μm and that phosphorylation is indispensable for these interactions as well. The crystal structure of the complex between a phosphorylated PPxY motif, and the SH2 domain of Vav2 reveals a conserved recognition mechanism.
Differentiation‐inducing factor 2 modulates chemotaxis via the histidine kinase DhkC‐dependent pathway in Dictyostelium discoideum
Authors: Kuwayama Hidekazu , Kubohara Yuzuru
Published: February 2016

Differentiation‐inducing factor 1(DIF‐1) and DIF‐2 are signaling molecules that control chemotaxis in Dictyostelium discoideum. Whereas DIF‐1 suppresses chemotaxis in shallow cAMP gradients, DIF‐2 enhances chemotaxis under the same conditions via a phosphodiesterase, response regulator A (RegA), which is a part of the DhkC–RdeA–RegA two‐component signaling system. In this study, to investigate the mechanism of the chemotaxis regulation by DIF‐2, we examined the effects of DIF‐2 (and DIF‐1) on chemotaxis in rdeA− and dhkC− mutant strains. In the parental wild‐type strains, chemotactic cell movement was suppressed with DIF‐1 and enhanced with DIF‐2 in shallow cAMP gradients. In contrast, in both rdeA− and dhkC− strains, chemotaxis was suppressed with DIF‐1 but unaffected by DIF‐2. The results suggest that DIF‐2 modulates chemotaxis via the DhkC–RdeA–RegA signaling system.
Estimated storage of amorphous silica in soils of the circum‐Arctic tundra region
Authors: Alfredsson H. , Clymans W. , Hugelius G. , Kuhry P. , Conley D. J.
Published: February 2016

We investigated the vertical distribution, storage, landscape partitioning, and spatial variability of soil amorphous silica (ASi) at four different sites underlain by continuous permafrost and representative of mountainous and lowland tundra, in the circum‐Arctic region. Based on a larger set of data, we present the first estimate of the ASi soil reservoir (0–1 m depth) in circum‐Arctic tundra terrain. At all sites, the vertical distribution of ASi concentrations followed the pattern of either (1) declining concentrations with depth (most common) or (2) increasing/maximum concentrations with depth. Our results suggest that a set of processes, including biological control, solifluction and other slope processes, cryoturbation, and formation of inorganic precipitates influence vertical distributions of ASi in permafrost terrain, with the capacity to retain stored ASi on millennial timescales. At the four study sites, areal ASi storage (0–1 m) is generally higher in graminoid tundra compared to wetlands. Our circum‐Arctic upscaling estimates, based on both vegetation and soil classification separately, suggest a storage amounting to 219 ± 28 and 274 ± 33 Tmol Si, respectively, of which at least 30% is stored in permafrost. This estimate would account for about 3% of the global soil ASi storage while occupying an equal portion of the global land area. This result does not support the hypothesis that the circum‐Arctic tundra soil ASi reservoir contains relatively higher amounts of ASi than other biomes globally as demonstrated for carbon. Nevertheless, climate warming has the potential to significantly alter ASi storage and terrestrial Si cycling in the Arctic.
The effective stress law at a brittle‐plastic transition with a halite gouge layer
Authors: Noda H. , Takahashi M.
Published: February 2016

We investigated the effect of pore pressure Pf near the brittle‐plastic transition (BPT) for a halite (NaCl) shear zone. Our series of precut friction experiments with a gas‐medium apparatus with temperature T ≤ 200°C, confining gas pressure Pc ≤ 150 MPa and Pf ≤ 140 MPa, revealed that a tanh connection between the brittle and plastic regimes works well even at elevated Pf, with a coefficient for Pf in an effective stress law α being unity. Plastic deformation around the real contacts independent of the mean stress results in α = 1 regardless of the ratio of the real contact area Ar/A. The functional dependency of the shear strength on the effective normal stress may deviate from a linear dependency with increasing Ar/A. The present findings support a smooth transition in a hypothetical steady state strength profile around a BPT, providing new insights in geologically obtained paleostress data in exhumed mylonitic shear zones.
A statistical study of magnetospheric ion composition along the geomagnetic field using the Cluster spacecraft forLvalues between 5.9 and 9.5
Authors: Sandhu J. K. , Yeoman T. K. , Fear R. C. , Dandouras I.
Published: February 2016

Using ion density data obtained by the CODIF (ion Composition and Distribution Function analyser) instrument on board the Cluster spacecraft, for the interval spanning 2001–2005, an empirical model describing the average ion mass distribution along closed geomagnetic field lines is determined. The empirical model describes the region spanning 5.9≤L< 9.5, with dependences onLshell and magnetic local time included, and represents ions in the energy range of 0.025 to 40 keV/charge. The data reduction process involves the identification and rejection of CODIF data contaminated by penetrating energetic radiation belt particles, found to frequently occur forL< 5.9. Furthermore, a comparison of data with observations of the cold plasma population in the region provides evidence that the CODIF data set is representative of the full plasma population. The variations in average ion mass along the field lines were modeled using a power law form, which maximizes toward the magnetic equatorial plane, with observed power law index values ranging between approximately −2.0 and 0.0. The resulting model illustrates some key features of the average ion mass spatial distribution, such as an average ion mass enhancement at lowLin the evening sector, indicating the transport of high‐latitude heavy ion outflows to the closed inner magnetosphere.
Data‐adaptive detection of transient deformation in geodetic networks
Authors: Walwer Damian , Calais Eric , Ghil Michael
Published: February 2016

The recent development of dense and continuously operating Global Navigation Satellite System (GNSS) networks worldwide has led to a significant increase in geodetic data sets that sometimes capture transient‐deformation signals. It is challenging, however, to extract such transients of geophysical origin from the background noise inherent to GNSS time series and, even more so, to separate them from other signals, such as seasonal redistributions of geophysical fluid mass loads. In addition, because of the very large number of continuously recording GNSS stations now available, it has become impossible to systematically inspect each time series and visually compare them at all neighboring sites. Here we show that Multichannel Singular Spectrum Analysis (M‐SSA), a method derived from the analysis of dynamical systems, can be used to extract transient deformations, seasonal oscillations, and background noise present in GNSS time series. M‐SSA is a multivariate, nonparametric, statistical method that simultaneously exploits the spatial and temporal correlations of geophysical fields. The method allows for the extraction of common modes of variability, such as trends with nonconstant slopes and oscillations shared across time series, without a priori hypotheses about their spatiotemporal structure or their noise characteristics. We illustrate this method using synthetic examples and show applications to actual GPS data from Alaska to detect seasonal signals and microdeformation at the Akutan active volcano. The geophysically coherent spatiotemporal patterns of uplift and subsidence thus detected are compared to the results of an idealized model of such processes in the presence of a magma chamber source.
Semi‐brittle flow of granitoid fault rocks in experiments
Authors: Pec Matej , Stünitz Holger , Heilbronner Renée , Drury Martyn
Published: February 2016

Field studies and seismic data show that semi‐brittle flow of fault rocks probably is the dominant deformation mechanism at the base of the seismogenic zone at the so‐called frictional‐viscous transition. To understand the physical and chemical processes accommodating semi‐brittle flow, we have performed an experimental study on synthetic granitoid fault rocks exploring a broad parameter space (temperature, T = 300, 400, 500, and 600°C, confining pressure, Pc ≈ 300, 500, 1000, and 1500 MPa, shear strain rate,
 ≈ 10−3, 10−4, 10−5, and 10−6 s−1, to finite shear strains, γ = 0–5). The experiments have been carried out using a granular material with grain size smaller than 200 µm with a little H2O added (0.2 wt %). Only two experiments (performed at the fastest strain rates and lowest temperatures) have failed abruptly right after reaching peak strength (τ ~ 1400 MPa). All other samples reach high shear stresses (τ ~ 570–1600 MPa) then weaken slightly (by Δτ ~ 10–190 MPa) and continue to deform at a more or less steady state stress level. Clear temperature dependence and a weak strain rate dependence of the peak as well as steady state stress levels are observed. In order to express this relationship, the strain rate‐stress sensitivity has been fit with a stress exponent, assuming γ̇ ∝ τn and yields high stress exponents (n ≈ 10–140), which decrease with increasing temperature. The microstructures show widespread comminution, strain partitioning, and localization into slip zones. The slip zones contain at first nanocrystalline and partly amorphous material. Later, during continued deformation, fully amorphous material develops in some of the slip zones. Despite the mechanical steady state conditions, the fabrics in the slip zones and outside continue to evolve and do not reach a steady state microstructure below γ = 5. Within the slip zones, the fault rock material progressively transforms from a crystalline solid to an amorphous material. We present and interpret the experimental results both in terms of sliding friction and viscous flow, and we discuss the possible effect that the formation of nanocrystalline and amorphous layers may have on earthquake nucleation.
Relating permeability and electrical resistivity in fractures using random resistor network models
Authors: Kirkby Alison , Heinson Graham , Krieger Lars
Published: February 2016

We use random resistor network models to explore the relationship between electrical resistivity and permeability in a fracture filled with an electrically conductive fluid. Fluid flow and current are controlled by both the distribution and the volume of pore space. Therefore, the aperture distribution of fractures must be accurately modeled in order to realistically represent their hydraulic and electrical properties. We have constructed fracture surface pairs based on characteristics measured on rock samples. We use these to construct resistor networks with variable hydraulic and electrical resistance in order to investigate the changes in both properties as a fault is opened. At small apertures, electrical conductivity and permeability increase moderately with aperture until the fault reaches its percolation threshold. Above this point, the permeability increases by 4 orders of magnitude over a change in mean aperture of less than 0.1 mm, while the resistivity decreases by up to a factor of 10 over this aperture change. Because permeability increases at a greater rate than matrix to fracture resistivity ratio, the percolation threshold can also be defined in terms of the matrix to fracture resistivity ratio, M. The value of M at the percolation threshold, MPT, varies with the ratio of rock to fluid resistivity, the fault spacing, and the fault offset. However, MPT is almost always less than 10. Greater M values are associated with fractures above their percolation threshold. Therefore, if such M values are observed over fluid‐filled fractures, it is likely that they are open for fluid flow.
Elastic softening in Fe7C3 with implications for Earth's deep carbon reservoirs
Authors: Liu Jiachao , Li Jie , Ikuta Daijo
Published: February 2016

Iron carbide Fe7C3 has recently emerged as a potential host of reduced carbon in Earth's mantle and a candidate component of the inner core, but the equation of state of Fe7C3 is still uncertain, partly because the nature of pressure‐induced magnetic transitions in Fe7C3 and their elastic effects remain controversial. Here we report the compression curve of hexagonal Fe7C3 in neon medium with dense pressure sampling and in comparison with pure iron in the same loading. The results revealed elastic softening between 7 GPa and 20 GPa, which can be attributed to noncollinear alignment of spin moments in a state between the ferromagnetic and paramagnetic phases, as expected for Invar‐type alloys. The volume reduction associated with the softening would enhance the stability of Fe7C3 in the deeper part of the upper mantle and transition zone. As a result of subsequent spin crossover at higher pressures, Fe7C3 at inner core conditions likely occurs as the nonmagnetic phase, which remains a candidate for the major component of the Earth's central sphere.
Dynamic friction in sheared fault gouge: Implications of acoustic vibration on triggering and slow slip
Authors: Lieou Charles K. C. , Elbanna Ahmed E. , Carlson Jean M.
Published: February 2016

Friction and deformation in granular fault gouge are among various dynamic interactions associated with seismic phenomena that have important implications for slip mechanisms on earthquake faults. To this end, we propose a mechanistic model of granular fault gouge subject to acoustic vibrations and shear deformation. The grain‐scale dynamics is described by the Shear‐Transformation‐Zone theory of granular flow, which accounts for irreversible plastic deformation in terms of flow defects whose density is governed by an effective temperature. Our model accounts for stick‐slip instabilities observed at seismic slip rates. In addition, as the vibration intensity increases, we observe an increase in the temporal advancement of large slip events, followed by a plateau and gradual decrease. Furthermore, slip becomes progressively slower upon increasing the vibration intensity. The results shed important light on the physical mechanisms of earthquake triggering and slow slip and provide essential elements for the multiscale modeling of earthquake ruptures. In particular, the results suggest that slow slip may be triggered by tremors.
Enhanced soil moisture drying in transitional regions under a warming climate
Authors: Cheng Shanjun , Huang Jianping
Published: February 2016

We analyzed global trends of soil moisture for the period 1948–2010 using the Global Land Data Assimilation System data set. Soil moisture was dominated by negative trends, with pronounced drying over East Asia and the Sahel. Spatial analysis according to climatic region revealed that the most obvious drying occurred over transitional regions between dry and wet climates. The noticeable drying first took place in the humid transitional regions and extended to the dry transitional regions, beginning in the 1980s. The variability of soil moisture was notably related to the changes in precipitation and temperature, but with different roles. For the global average, precipitation had a dominant effect on the variability of soil moisture at interannual to decadal time scales, but temperature was the main cause of the long‐term trend of soil moisture on the whole. The enhanced soil drying in the transitional regions was primarily caused by global warming, which is illustrated by regression analysis and the land surface model.
Paleoseawater density reconstruction and its implication for cold‐water coral carbonate mounds in the northeast Atlantic through time
Authors: Rüggeberg Andres , Flögel Sascha , Dullo Wolf‐Christian , Raddatz Jacek , Liebetrau Volker
Published: February 2016

Carbonate buildups and mounds are impressive biogenic structures throughout Earth history. In the recent NE Atlantic, cold‐water coral (CWC) reefs form giant carbonate mounds of up to 300 m of elevation. The expansion of these coral carbonate mounds is paced by climatic changes during the past 2.7 Myr. Environmental control on their development is directly linked to controls on its main constructors, the reef‐building CWCs. Seawater density has been identified as one of the main controlling parameter of CWC growth in the NE Atlantic. One possibility is the formation of a pycnocline above the carbonate mounds, which is increasing the hydrodynamic regime, supporting elevated food supply, and possibly facilitating the distribution of coral larvae. The potential to reconstruct past seawater densities from stable oxygen isotopes of benthic foraminifera has been further developed: a regional equation gives reliable results for three different settings,peak interglacials(e.g., Holocene),peak glacials(e.g., Last Glacial Maximum), andintermediatesetting (between the two extremes). Seawater densities are reconstructed for two different NE Atlantic CWC carbonate mounds in the Porcupine Seabight indicating that the development of carbonate mounds is predominantly found at a seawater density range between 27.3 and 27.7 kg m−3(σΘnotation). Comparable to recent conditions, we interpret the reconstructed density range as a pycnocline serving as boundary layer, on which currents develop, carrying nutrition and possibly coral larvae. The close correlation of CWC reef growth with reconstructed seawater densities through the Pleistocene highlights the importance of pycnoclines and intermediate water mass dynamics.
On the reconstruction of ocean circulation and climate based on the “Gardar Drift”
Authors: Langehaug H. R. , Mjell T. L. , Otterå O. H. , Eldevik T. , Ninnemann U. S. , Kleiven H. F.
Published: February 2016

Sediment‐based reconstructions of bottom water velocity at the Gardar Drift are commonly interpreted to reflect changes in the eastern Nordic Seas overflows. Here we investigate the relationship between changes in the water that overflows through the Faroe Shetland Channel and downstream bottom velocity at the location of the Gardar Drift as represented in a 500 year long simulation with the Bergen Climate Model. We identify a region in our simulation proximal to the geographical location of the northern Gardar Drift where 76% of the variance in bottom velocity can be explained by changes in the volume transport and density of the Faroe Shetland Channel overflow. By contrast, Labrador Sea Water changes do not appear to play a significant role in the bottom flow over the Gardar Drift. Our findings support the assumption in the paleo literature that reconstructions of bottom water velocity at the Gardar Drift reflect past changes in the eastern Nordic Seas overflows. However, our results suggest that velocity changes downstream are not a simple metric for the strength of the overflow, rather overflow density plays the largest role.
Lithospheric structure of Central Europe: Puzzle pieces from Pannonian Basin to Trans‐European Suture Zone resolved by geophysical‐petrological modeling
Authors: Alasonati Tašárová Zuzana , Fullea Javier , Bielik Miroslav , Środa Piotr
Published: February 2016

We have analyzed the thermochemical structure of the mantle in Central Europe, a complex area with a highly heterogeneous lithospheric structure reflecting the interplay of contraction, strike slip, subduction, and extension tectonics. Our modeling is based on an integrative 3‐D approach (LitMod) that combines in a self‐consistent manner concepts and data from thermodynamics, mineral physics, geochemistry, petrology, and solid Earth geophysics. This approach minimizes uncertainties of the estimates derived from modeling of various data sets separately. To further constrain our 3‐D model we have made use of the vast geophysical and geological data (2‐D and 3‐D, shallow/crustal versus deep lithospheric experiments) based on experiments performed in Central Europe in the past decades. Given the amount and the different nature/resolution of the available constraints, one of the most challenging tasks of this study was to consistently combine them, finding a trade‐off between all local and regional data sets available in a way that (i) preserves as many structural details as possible and (ii) summarizes those data sets into a single robust regional model. The resulting P/T‐dependent mantle densities are in LitMod 3‐D calculated based on a given mineralogical composition. They therefore provide more reliable estimates compared to pure gravity models, which enhance modeling of the crustal structures. Our results clearly indicate presence of several lithospheric domains characterized by distinct features, Pannonian Basin being one of the most outstanding ones. It has the thinnest crust and lithosphere in the area modeled, characterized by relatively fertile composition.
Dispersion and dissolution of a buoyancy driven gas plume in a layered permeable rock
Authors: Woods Andrew W. , Norris Simon
Published: February 2016

Using a series of simplified models, we explore the controls on the migration, dispersion and eventual dissolution of a plume of hydrogen gas which may, in principle, rise under buoyancy through a layered permeable rock if released from a Geological Disposal Facility (GDF). We show that the presence of low permeability shale barriers causes the gas to spread laterally as it rises. Averaging over the length scale of the barriers, we use expressions for the Darcy velocity of the gas to describe the dispersion of a tracer and illustrate the effect with a new experiment using a baffled Hele‐Shaw cell. While the plume is flowing, a large volume of gas may build up beneath the barriers. If the gas flux subsequently wanes, much of the gas will drain upward through the formation and spread on the upper impermeable boundary of the formation. However, a significant capillary‐trapped wake of gas may develop beneath each barrier. Owing to the low solubility of hydrogen in water and assuming relatively slow groundwater flow rates, this trapped hydrogen may require a period of tens to hundreds of thousands of years to dissolve and form a cloud of hydrogen rich water. Although simplified, these models provide a framework to assess the possible travel times and pathways of such a gas plume.
The implication of nonradiative energy fluxes dominating Greenland ice sheet exceptional ablation area surface melt in 2012
Authors: Fausto Robert S. , van As Dirk , Box Jason E. , Colgan William , Langen Peter L. , Mottram Ruth H.
Published: February 2016

During two exceptionally large July 2012 multiday Greenland ice sheet melt episodes, nonradiative energy fluxes (sensible, latent, rain, and subsurface collectively) dominated the ablation area surface energy budget of the southern and western ice sheet. On average the nonradiative energy fluxes contributed up to 76% of daily melt energy at nine automatic weather station sites in Greenland. Comprising 6% of the ablation period, these powerful melt episodes resulted in 12–15% of the south and west Greenland automatic weather station annual ablation totals. Analysis of high resolution (~5 km) HIRHAM5 regional climate model output indicates widespread dominance of nonradiative energy fluxes across the western ablation area during these episodes. Yet HIRHAM5 still underestimates melt by up to 56% during these episodes due to a systematic underestimation of turbulent energy fluxes typical of regional climate models. This has implications for underestimating future melt, when exceptional melt episodes are expected to occur more frequently.
Response of northern winter polar cap to auroral substorms
Authors: Liou Kan , Sotirelis Thomas
Published: February 2016

The three‐phase substorm sequence has been generally accepted and is often tied to the Dungey cycle. Although previous studies have mostly agreed on the increase and decrease in the polar cap area during an episode of substorm, there are disparate views on when the polar cap starts to contract relative to substorm onset. Here we address this conflict using high‐resolution (~1–3 min) snapshot global auroral images from the ultraviolet imager on board the Polar spacecraft. On the basis of 28 auroral substorm events, all observed in the Northern Hemispheric winter, it is found that the polar cap inflated prior to onset in all events and it attained the largest area ~6 min prior to the substorm expansion phase onset, while the dayside polar cap area remained steady around the onset. The onset of nightside polar cap deflation is found to be attributed to intensifications of aurora on the poleward edge of the nightside oval, mostly in the midnight sector. Although this result supports the loading‐unloading and reconnection substorm models, it is not clear if the initial polar cap deflation and the substorm expansion are parts of the same process.
Fast and slow precipitation responses to individual climate forcers: A PDRMIP multimodel study
Authors: Samset B. H. , Myhre G. , Forster P. M. , Hodnebrog Ø. , Andrews T. , Faluvegi G. , Fläschner D. , Kasoar M. , Kharin V. , Kirkevåg A. , Lamarque J.‐F. , Olivié D. , Richardson T. , Shindell D. , Shine K. P. , Takemura T. , Voulgarakis A.
Published: February 2016

Precipitation is expected to respond differently to various drivers of anthropogenic climate change. We present the first results from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), where nine global climate models have perturbed CO2, CH4, black carbon, sulfate, and solar insolation. We divide the resulting changes to global mean and regional precipitation into fast responses that scale with changes in atmospheric absorption and slow responses scaling with surface temperature change. While the overall features are broadly similar between models, we find significant regional intermodel variability, especially over land. Black carbon stands out as a component that may cause significant model diversity in predicted precipitation change. Processes linked to atmospheric absorption are less consistently modeled than those linked to top‐of‐atmosphere radiative forcing. We identify a number of land regions where the model ensemble consistently predicts that fast precipitation responses to climate perturbations dominate over the slow, temperature‐driven responses.
Controlled Mechanical Buckling for Origami‐Inspired Construction of 3D Microstructures in Advanced Materials
Authors: Yan Zheng , Zhang Fan , Wang Jiechen , Liu Fei , Guo Xuelin , Nan Kewang , Lin Qing , Gao Mingye , Xiao Dongqing , Shi Yan , Qiu Yitao , Luan Haiwen , Kim Jung Hwan , Wang Yiqi , Luo Hongying , Han Mengdi , Huang Yonggang , Zhang Yihui , Rogers John A.
Published: February 2016

Origami is a topic of rapidly growing interest in both the scientific and engineering research communities due to its promising potential in a broad range of applications. Previous assembly approaches for origami structures at the micro/nanoscale are constrained by the applicable classes of materials, topologies, and/or capability for reversible control over the transformation process. Here, a strategy is introduced that exploits mechanical buckling for autonomic origami assembly of 3D structures across material classes from soft polymers to brittle inorganic semiconductors, and length scales from nanometers to centimeters. This approach relies on a spatial variation of thickness in the initial 2D structures as a means to produce engineered folding creases during the compressive buckling process. The elastic nature of the assembly scheme enables active, deterministic control over intermediate states in the 2D to 3D transformation in a continuous and reversible manner. Demonstrations include a broad set of 3D structures formed through unidirectional, bidirectional, and even hierarchical folding, with examples ranging from half cylindrical columns and fish scales, to cubic boxes, pyramids, starfish, paper fans, skew tooth structures, and to amusing system‐level examples of soccer balls, model houses, cars, and multifloor textured buildings.
Guided Formation of 3D Helical Mesostructures by Mechanical Buckling: Analytical Modeling and Experimental Validation
Authors: Liu Yuan , Yan Zheng , Lin Qing , Guo Xuelin , Han Mengdi , Nan Kewang , Hwang Keh‐Chih , Huang Yonggang , Zhang Yihui , Rogers John A.
Published: February 2016

3D helical mesostructures are attractive for applications in a broad range of microsystem technologies due to their mechanical and electromagnetic properties as stretchable interconnects, radio frequency antennas, and others. Controlled compressive buckling of 2D serpentine‐shaped ribbons provides a strategy to formation of such structures in wide ranging classes of materials (from soft polymers to brittle inorganic semiconductors) and length scales (from nanometer to centimeter), with an ability for automated, parallel assembly over large areas. The underlying relations between the helical configurations and fabrication parameters require a relevant theory as the basis of design for practical applications. Here, an analytic model of compressive buckling in serpentine microstructures is presented based on the minimization of total strain energy that results from various forms of spatially dependent deformations. Experiments at micro‐ and millimeter scales, together with finite element analyses, have been exploited to examine the validity of developed model. The theoretical analyses shed light on general scaling laws in terms of three groups of fabrication parameters (related to loading, material, and 2D geometry), including a negligible effect of material parameters and a square root dependence of primary displacements on the compressive strain. Furthermore, analytic solutions were obtained for the key physical quantities (e.g., displacement, curvature and maximum strain). A demonstrative example illustrates how to leverage the analytic solutions in choosing the various design parameters, such that brittle fracture or plastic yield can be avoided in the assembly process.
Electrochemical Synthesis and Characterization of Interpenetrating Networks of Conducting Polymers for Enhanced Charge Storage
Authors: Admassie Shimelis , Elfwing Anders , Inganäs Olle
Published: February 2016

A supercapacitor electrode consisting of an interpenetrating network of poly(aminoanthraquinone) (PAAQ) and poly(3,4‐ethylenedioxythiophene) (PEDOT) is synthesized by a simple two‐step galvanostatic deposition and characterized by electrochemical methods. By electrodepositing PEDOT on top of PAAQ, it is possible to access the quinones in PAAQ and as a result the specific capacitance of PAAQ increases from 90 to 383 F g−1 and also significantly improves the charge‐storage capacity from 25 to 106 mAh g−1 at a discharge current of 1 A g−1. These values are also significantly higher than most reported values for PEDOT and hybrids. Moreover, the hybrid material shows excellent stability with 91% of the initial capacitance being retained after 2000 cycles at a discharge rate of 2 A g−1.