6,448 research outputs found
Histologic and Clinical Follow-up of Thyroid Fine Needle Aspirates in Pediatric Patients
BACKGROUND
Although fine-needle aspiration (FNA) has an important role in evaluating thyroid nodules in adults, there is little published information regarding its utility in the pediatric population.
METHODS
A retrospective analysis of thyroid FNAs for patients who were 18 years old or younger at 2 institutions was conducted. Aspirates were retrospectively categorized with the Bethesda System for Reporting Thyroid Cytopathology. These diagnoses were then correlated with either final histopathology or clinical follow-up.
RESULTS
A total of 186 thyroid FNA samples from 154 patients (122 females and 32 males), who ranged in age from 9 months to 18 years (median, 16 years; mean, 14 years), were identified. FNA was performed to evaluate 1 to 3 nodules for each patient. Aspirates were classified as follows: nondiagnostic (n = 27), benign (n = 114), atypia of undetermined significance (AUS; n = 21), follicular neoplasm (FN; n = 8), suspicious for malignancy (n = 3), and malignant (n = 13). Sixty-one samples had a histologic correlation, 68 were followed clinically for ≥2 years, and 57 either had no follow-up or were followed for <2 years. For statistical purposes, FNA diagnoses of suspicious and malignant were considered positive, and benign lesions were considered negative. The accuracy was 99%, and the sensitivity and specificity were 94% and 100%, respectively. The risk of malignancy, not including papillary microcarcinoma, was 2% for benign aspirates, 21% for AUS, 57% for FN, and 100% for suspicious or malignant aspirates.
CONCLUSIONS
This analysis demonstrates that FNA is a sensitive and highly specific modality for evaluating thyroid nodules in pediatric patients. Each diagnostic category can facilitate communication and guide appropriate management
Strong-field general relativity and quasi-periodic oscillations in x-ray binaries
Quasi-periodic oscillations (QPOs) at frequencies near 1000 Hz were recently
discovered in several x-ray binaries containing neutron stars. Two sources show
no correlation between QPO frequency and source count rate (Berger et al. 1996,
Zhang et al. 1996). We suggest that the QPO frequency is determined by the
Keplerian orbital frequency near the marginally stable orbit predicted by
general relativity in strong gravitational fields (Muchotrzeb-Czerny 1986,
Paczynski 1987, Kluzniak et al. 1990). The QPO frequencies observed from 4U
1636-536 imply that the mass of the neutron star is 2.02 +/- 0.12 solar masses.
Interpretation of the 4.1 keV absorption line observed from 4U 1636-536 (Waki
et al. 1984) as due to Fe XXV ions then implies a neutron star radius of 9.6
+/-0.6 km.Comment: 4 pages, uses aas2pp4.sty, submitted to ApJ
Large-scale Graphitic Thin Films Synthesized on Ni and Transferred to Insulators: Structural and Electronic Properties
We present a comprehensive study of the structural and electronic properties
of ultrathin films containing graphene layers synthesized by chemical vapor
deposition (CVD) based surface segregation on polycrystalline Ni foils then
transferred onto insulating SiO2/Si substrates. Films of size up to several
mm's have been synthesized. Structural characterizations by atomic force
microscopy (AFM), scanning tunneling microscopy (STM), cross-sectional
transmission electron microscopy (XTEM) and Raman spectroscopy confirm that
such large scale graphitic thin films (GTF) contain both thick graphite regions
and thin regions of few layer graphene. The films also contain many wrinkles,
with sharply-bent tips and dislocations revealed by XTEM, yielding insights on
the growth and buckling processes of the GTF. Measurements on mm-scale
back-gated transistor devices fabricated from the transferred GTF show
ambipolar field effect with resistance modulation ~50% and carrier mobilities
reaching ~2000 cm^2/Vs. We also demonstrate quantum transport of carriers with
phase coherence length over 0.2 m from the observation of 2D weak
localization in low temperature magneto-transport measurements. Our results
show that despite the non-uniformity and surface roughness, such large-scale,
flexible thin films can have electronic properties promising for device
applications.Comment: This version (as published) contains additional data, such as cross
sectional TEM image
The effects of weak disorders on Quantum Hall critical points
We study the consequences of random mass, random scalar potential and random
vector potential on the line of clean fixed points between integer/fractional
quantum Hall states and an insulator. This line of fixed points was first
identified in a clean Dirac fermion system with both Chern-Simon coupling and
Coulomb interaction in Phys. Rev. Lett. {\bf 80}, 5409 (1998). By performing a
Renormalization Group analysis in 1/N (N is the No. of species of Dirac
fermions) and the variances of three disorders , we find that is irrelevant along this line, both
and are marginal. With the presence of all the three
disorders, the pure fixed line is unstable. Setting Chern-Simon interaction to
zero, we find one non-trivial line of fixed points in plane
with dynamic exponent z=1 and continuously changing , it is stable against
small in a small range of the line ,
therefore it may be relevant to integer quantum Hall transition. Setting
, we find a fixed plane with z=1, the part of this plane with
is stable against small , therefore it may be relevant to
fractional quantum Hall transition.Comment: 16 pages, 19 figure
More Filtering on SNP Calling Does Not Remove Evidence of Inter-Nucleus Recombination in Dikaryotic Arbuscular Mycorrhizal Fungi
Evidence for the existence of dikaryote-like strains, low nuclear sequence diversity and inter-nuclear recombination in arbuscular mycorrhizal fungi has been recently reported based on single nucleus sequencing data. Here, we aimed to support evidence of inter-nuclear recombination using an approach that filters SNP calls more conservatively, keeping only positions that are exclusively single copy and homozygous, and with at least five reads supporting a given SNP. This methodology recovers hundreds of putative inter-nucleus recombination events across publicly available sequence data from individual nuclei. Challenges related to the acquisition and analysis of sequence data from individual nuclei are highlighted and discussed, and ways to address these issues in future studies are presented
Observational evidence for the convective transport of dust over the central United States
Bulk aerosol composition and aerosol size distributions measured aboard the DC-8 aircraft during the Deep Convective Clouds and Chemistry Experiment mission in May/June 2012 were used to investigate the transport of mineral dust through nine storms encountered over Colorado and Oklahoma. Measurements made at low altitudes (\u3c5 km mean sea level (MSL)) in the storm inflow region were compared to those made in cirrus anvils (altitude \u3e 9 km MSL). Storm mean outflow Ca2+ mass concentrations and total coarse (1 µm \u3c diameter \u3c 5 µm) aerosol volume (Vc) were comparable to mean inflow values as demonstrated by average outflow/inflow ratios greater than 0.5. A positive relationship between Ca2+, Vc, ice water content, and large (diameter \u3e 50 µm) ice particle number concentrations was not evident; thus, the influence of ice shatter on these measurements was assumed small. Mean inflow aerosol number concentrations calculated over a diameter range (0.5 µm \u3c diameter \u3c 5.0 µm) relevant for proxy ice nuclei (NPIN) were ~15–300 times higher than ice particle concentrations for all storms. Ratios of predicted interstitial NPIN (calculated as the difference between inflow NPIN and ice particle concentrations) and inflow NPIN were consistent with those calculated for Ca2+ and Vc and indicated that on average less than 10% of the ingested NPIN were activated as ice nuclei during anvil formation. Deep convection may therefore represent an efficient transport mechanism for dust to the upper troposphere where these particles can function as ice nuclei cirrus forming in situ
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