Topologically-forced electro-modulation of friction

Controlling the friction between sliding surfaces via their electric potential (electro-modulation) is a long-standing tribological goal. Phospholipid assemblies, whether as continuous bilayers or as close-packed vesicles (liposomes), form highly-lubricious surface boundary layers in aqueous media, via the hydration lubrication mechanism at the lipid-lipid interfaces, with friction coefficients {\mu}(= [force to slide]/load) down to 10-4, thus offering scope for large friction changes. Here we show that the friction between two such lipid-coated surfaces can be massively modulated through very small potentials applied to one of them, changing reversibly by up to 200-fold or more. Atomistic simulations indicate that this arises from (fully reversible) electroporation of the lipid bilayers under the potential-driven inter-surface electric fields. The porated topology of the bilayers leads to increased dehydration-induced attraction between the headgroups of opposing bilayers; at the same time, the porated bilayer structures may bridge the gap between the sliding surfaces. These effects act in parallel to modulate the friction by topologically-forcing the slip plane to pass through the intra-bilayer acyl tail interface, for which {\mu}{\approx}0.1. This enables facile, fully-reversible electro-modulation of the friction, with a dynamic range up to some 2 orders of magnitude larger than achieved to date.Comment: Yu Zhang and Di Jin contributes equally to this wor

Digit-only sauropod pes trackways from China – evidence of swimming or a preservational phenomenon?

For more than 70 years unusual sauropod trackways have played a pivotal role in debates about the swimming ability of sauropods. Most claims that sauropods could swim have been based on manusonly or manus-dominated trackways. However none of these incomplete trackways has been entirely convincing, and most have proved to be taphonomic artifacts, either undertracks or the result of differential depth of penetration of manus and pes tracks, but otherwise showed the typical pattern of normal walking trackways. Here we report an assemblage of unusual sauropod tracks from the Lower Cretaceous Hekou Group of Gansu Province, northern China, characterized by the preservation of only the pes claw traces, that we interpret as having been left by walking, not buoyant or swimming, individuals. They are interpreted as the result of animals moving on a soft mud-silt substrate, projecting their claws deeply to register their traces on an underlying sand layer where they gained more grip during progression. Other sauropod walking trackways on the same surface with both pes and manus traces preserved, were probably left earlier on relatively firm substrates that predated the deposition of soft mud and silt . Presently, there is no convincing evidence of swimming sauropods from their trackways, which is not to say that sauropods did not swim at all

Glial Choristoma in the Middle Ear and Mastoid Bone: A Case Report

Heterotopic brain tissue usually involves extracranial midline structures of the head and neck such as nose, nasopharynx, and oral cavity. Its occurrence in the non-midline structures, including middle ear, is rare. We described a 50-yr-old-man with heterotopic glial tissue in the middle ear and mastoid bone. The patient presented with progressive hearing loss for 8 yr. There was no history of congenital anomalies, trauma, or ear surgery. Computed tomography revealed a mass-like lesion with soft tissue density occupying the middle ear cavity and mastoid antrum. At the operation, a graywhite fibrotic mass was detected in the epitympanic area. Mesotympanum and ossicles were intact. The patient underwent left simple mastoidectomy with type I tympanoplasty. During operation, definite cranial bone defect or cerebrospinal fluid leakage was not found. Histologically, the lesion was composed of exclusively mature, disorganized glial tissue with fibrovascular elements in a rather loose fibrillary background. Glial tissue showed diffuse positive reaction for glial fibrillar acidic protein and S100 protein on immunohistochemical study

C-axis electronic Raman scattering in Bi_2Sr_2CaCu_2O_{8+\delta}

We report a c-axis-polarized electronic Raman scattering study of Bi_2Sr_2CaCu_2O_{8+\delta} single crystals. In the normal state, a resonant electronic continuum extends to 1.5 eV and gains significant intensity as the incoming photon energy increases. In the superconducting state, a coherence 2\Delta peak appears around 50 meV, with a suppression of the scattering intensity at frequencies below the peak position. The peak energy, which is higher than that seen with in-plane polarizations, signifies distinctly different dynamics of quasiparticle excitations created with out-of-plane polarization.Comment: 12 pages, REVTEX, 3 postscript figure

SHARC-II 350 micron Observations of Thermal Emission from Warm Dust in z>=5 Quasars

We present observations of four z>= SDSS quasars at 350 micron with the SHARC-II bolometer camera on the Caltech Submillimeter Observatory. These are among the deepest observations that have been made by SHARC-II at 350 micron, and three quasars are detected at >=3 sigma significance, greatly increasing the sample of 350 micron (corresponds to rest frame wavelengths of <60 micron at z>=5), detected high-redshift quasars. The derived rest frame far-infrared (FIR) emission in the three detected sources is about five to ten times stronger than that expected from the average SED of the local quasars given the same 1450A luminosity. Combining the previous submillimeter and millimeter observations at longer wavelengths, the temperatures of the FIR-emitting warm dust from the three quasar detections are estimated to be in the range of 39 to 52 K. Additionally, the FIR-to-radio SEDs of the three 350 micron detections are consistent with the emission from typical star forming galaxies. The FIR luminosities are ~10^{13} L_solar and the dust masses are >= 10^{8}M_solar. These results confirm that huge amounts of warm dust can exist in the host galaxies of optically bright quasars as early as z~6. The universe is so young at these epochs (~1 Gyr) that a rapid dust formation mechanism is required. We estimate the size of the FIR dust emission region to be about a few kpc, and further provide a comparison of the SEDs among different kinds of dust emitting sources to investigate the dominant dust heating mechanism.Comment: 15 pages, 3 figures, accepted for publication in A

Optimally Repeatable Kinetic Model Variant for Myocardial Blood Flow Measurements with 82Rb PET

Purpose. Myocardial blood flow (MBF) quantification with R b 82 positron emission tomography (PET) is gaining clinical adoption, but improvements in precision are desired. This study aims to identify analysis variants producing the most repeatable MBF measures. Methods. 12 volunteers underwent same-day test-retest rest and dipyridamole stress imaging with dynamic R b 82 PET, from which MBF was quantified usin

Caregiver-reported delay in presentation to pediatric emergency departments for fear of contracting COVID-19: a multi-national cross-sectional study

Objective: To determine if caregivers of children presenting to pediatric emergency departments (EDs) during the COVID-19 pandemic are delaying presenting to care for fear of contracting COVID-19. Methods: This was a pre-planned secondary analysis of a cross-sectional survey study of caregivers accompanying their children aged 0-19 years to 16 pediatric EDs in 5 countries from May to June 2020. An anonymous online survey, completed by caregivers via RedCAP, included caregiver and child demographics, presenting complaints, if they delayed presentation and whether symptoms worsened during this interval, as well as caregiver concern about the child or caregiver having COVID-19 at the time of ED visit. Results: Of 1543 caregivers completing the survey, 287 (18.6%) reported a delay in seeking ED care due to concerns of contracting COVID-19 in the hospital. Of those, 124 (43.2%) stated their child's symptoms worsened during the waiting interval. Caregiver relationship to child [mother] (OR 1.85, 95% CI 1.27-2.76), presence of chronic illness in child (OR 1.78. 95% CI 1.14-2.79), younger age of caregiver (OR 0.965, 95% CI 0.943-0.986), and caregiver concerns about lost work during the pandemic (OR 1.08, 95% CI 1.04-1.12) were independently associated with a COVID-19-related delayed presentation in multivariable regression analysis. Conclusions: Almost one in five caregivers reported delaying ED presentation for their ill or injured child specifically due to fear of contracting COVID-19 while in hospital, with mothers, younger caregivers, caregivers of children with chronic illness, and those concerned about lost work more likely to report delaying ED presentation. Keywords: COVID-19; Caregivers; Children; Emergency department; Presentation dela

Integration of hybridization-based markers (overgos) into physical maps for comparative and evolutionary explorations in the genus Oryza and in Sorghum

BACKGROUND: With the completion of the genome sequence for rice (Oryza sativa L.), the focus of rice genomics research has shifted to the comparison of the rice genome with genomes of other species for gene cloning, breeding, and evolutionary studies. The genus Oryza includes 23 species that shared a common ancestor 8–10 million years ago making this an ideal model for investigations into the processes underlying domestication, as many of the Oryza species are still undergoing domestication. This study integrates high-throughput, hybridization-based markers with BAC end sequence and fingerprint data to construct physical maps of rice chromosome 1 orthologues in two wild Oryza species. Similar studies were undertaken in Sorghum bicolor, a species which diverged from cultivated rice 40–50 million years ago. RESULTS: Overgo markers, in conjunction with fingerprint and BAC end sequence data, were used to build sequence-ready BAC contigs for two wild Oryza species. The markers drove contig merges to construct physical maps syntenic to rice chromosome 1 in the wild species and provided evidence for at least one rearrangement on chromosome 1 of the O. sativa versus Oryza officinalis comparative map. When rice overgos were aligned to available S. bicolor sequence, 29% of the overgos aligned with three or fewer mismatches; of these, 41% gave positive hybridization signals. Overgo hybridization patterns supported colinearity of loci in regions of sorghum chromosome 3 and rice chromosome 1 and suggested that a possible genomic inversion occurred in this syntenic region in one of the two genomes after the divergence of S. bicolor and O. sativa. CONCLUSION: The results of this study emphasize the importance of identifying conserved sequences in the reference sequence when designing overgo probes in order for those probes to hybridize successfully in distantly related species. As interspecific markers, overgos can be used successfully to construct physical maps in species which diverged less than 8 million years ago, and can be used in a more limited fashion to examine colinearity among species which diverged as much as 40 million years ago. Additionally, overgos are able to provide evidence of genomic rearrangements in comparative physical mapping studies

Prevalence of tick-borne encephalitis virus in ticks from southern Korea

The prevalence of tick-borne encephalitis virus (TBEV) in southern Korea was determined by collecting ticks using tick drags. A total of 4,077 of 6,788 ticks collected were pooled (649 pools) according to collection site, species, and developmental stage and assayed for TBEV. The TBEV protein E and NS5 gene fragments were detected using RT-nested PCR in six pools of nymphs collected from Jeju Island (2,491 ticks). The minimum field detection rates for TBEV were 0.17% and 0.14% for Haemaphysalis longicornis and Haemayphysalis flava nymphs, respectively. The 252 bp NS5 and 477 bp protein E gene amplicons were sequenced. Phylogenetic analysis showed that the NS5 and protein E genes of the Jeju strain were clustered with Western subtype (98.0% and 99.4% identity, respectively). The Western subtype of TBEV is endemic in Korea, including Jeju Island. The study of vector and zoonotic host susceptibility to TBEV is required to better understand its potential impact on public health