4,331 research outputs found
Solar Irradiance Variability is Caused by the Magnetic Activity on the Solar Surface
The variation in the radiative output of the Sun, described in terms of solar
irradiance, is important to climatology. A common assumption is that solar
irradiance variability is driven by its surface magnetism. Verifying this
assumption has, however, been hampered by the fact that models of solar
irradiance variability based on solar surface magnetism have to be calibrated
to observed variability. Making use of realistic three-dimensional
magnetohydrodynamic simulations of the solar atmosphere and state-of-the-art
solar magnetograms from the Solar Dynamics Observatory, we present a model of
total solar irradiance (TSI) that does not require any such calibration. In
doing so, the modeled irradiance variability is entirely independent of the
observational record. (The absolute level is calibrated to the TSI record from
the Total Irradiance Monitor.) The model replicates 95% of the observed
variability between April 2010 and July 2016, leaving little scope for
alternative drivers of solar irradiance variability at least over the time
scales examined (days to years).Comment: Supplementary Materials;
https://journals.aps.org/prl/supplemental/10.1103/PhysRevLett.119.091102/supplementary_material_170801.pd
Reconstruction of spectral solar irradiance since 1700 from simulated magnetograms
We present a reconstruction of the spectral solar irradiance since 1700 using
the SATIRE-T2 (Spectral And Total Irradiance REconstructions for the Telescope
era version 2) model. This model uses as input magnetograms simulated with a
surface flux transport model fed with semi-synthetic records of emerging
sunspot groups. We used statistical relationships between the properties of
sunspot group emergence, such as the latitude, area, and tilt angle, and the
sunspot cycle strength and phase to produce semi-synthetic sunspot group
records starting in the year 1700. The semisynthetic records are fed into a
surface flux transport model to obtain daily simulated magnetograms that map
the distribution of the magnetic flux in active regions (sunspots and faculae)
and their decay products on the solar surface. The magnetic flux emerging in
ephemeral regions is accounted for separately based on the concept of extended
cycles whose length and amplitude are linked to those of the sunspot cycles
through the sunspot number. The magnetic flux in each surface component
(sunspots, faculae and network, and ephemeral regions) was used to compute the
spectral and total solar irradiance between the years 1700 and 2009. This
reconstruction is aimed at timescales of months or longer although the model
returns daily values. We found that SATIRE-T2, besides reproducing other
relevant observations such as the total magnetic flux, reconstructs the total
solar irradiance (TSI) on timescales of months or longer in good agreement with
the PMOD composite of observations, as well as with the reconstruction starting
in 1878 based on the RGO-SOON data. The model predicts an increase in the TSI
of 1.2[+0.2, -0.3] Wm-2 between 1700 and the present. The spectral irradiance
reconstruction is in good agreement with the UARS/SUSIM measurements as well as
the Lyman-alpha composite.Comment: 13 pages, 10 figure
UV solar irradiance in observations and the NRLSSI and SATIRE-S models
Total solar irradiance and UV spectral solar irradiance have been monitored
since 1978 through a succession of space missions. This is accompanied by the
development of models aimed at replicating solar irradiance by relating the
variability to solar magnetic activity. The NRLSSI and SATIRE-S models provide
the most comprehensive reconstructions of total and spectral solar irradiance
over the period of satellite observation currently available. There is
persistent controversy between the various measurements and models in terms of
the wavelength dependence of the variation over the solar cycle, with
repercussions on our understanding of the influence of UV solar irradiance
variability on the stratosphere. We review the measurement and modelling of UV
solar irradiance variability over the period of satellite observation. The
SATIRE-S reconstruction is consistent with spectral solar irradiance
observations where they are reliable. It is also supported by an independent,
empirical reconstruction of UV spectral solar irradiance based on UARS/SUSIM
measurements from an earlier study. The weaker solar cycle variability produced
by NRLSSI between 300 and 400 nm is not evident in any available record. We
show that although the method employed to construct NRLSSI is principally
sound, reconstructed solar cycle variability is detrimentally affected by the
uncertainty in the SSI observations it draws upon in the derivation. Based on
our findings, we recommend, when choosing between the two models, the use of
SATIRE-S for climate studies
Surface Acoustic Wave Driven Microchannel Flow
We demonstrate that the propagation of surface acoustic waves, arising from the excitation of the acoustic field on a piezoelectric crystal (lithium niobate) substrate, along the sidewalls of microchannels (50 Ī¼m or 280 Ī¼m wide and 200 Ī¼m deep) fabricated in the substrate, can give rise to throughflow with velocities of the order 10 mm/s. This streaming flow in the direction along which the surface acoustic wave propagates is a result of the leakage of acoustic radiation from the substrate walls into the fluid. Good agreement is obtained between these preliminary experimental results with those from numerical simulations of the classical acoustic streaming model. In any case, these results show the potential of surface acoustic wave micropumps to be an effective fluid-driving mechanism for microfluidic devices
Breastfeeding Education in Term of Knowledge and Attitude Through Mother Support Group
Knowledge and attitude are important factors for successful breastfeeding practice. The objective of this study was to examine the influence of knowledge and attitude on breastfeeding among Indonesian mothers who joined mother support group (MSG) program. This was a community based cross-sectional study. There were 221 mothers participated on this study. Multiple regression was used to asses the influence of knowledge and attitude on breastfeeding. Result of the study showed that knowledge and attitude influence breastfeeding practice
Microfluidic Channel Fabrication in Lithium Niobate using Focused Ion Beam
Microfluidic channels are fabricated in lithium niobate (LN) by Focused Ion Beam (FIB) milling. 127.68Ā° axis rotated Y-cut (SAW grade) and Z-cut LN wafers are used. Material removal rate is 0.34Ā±0.02 Āµm3/nC for Y-cut sample and 0.30 Ā± 0.02Āµm/nC for Z-cut sample. Experimental results show that the material removal rate decreases at high ion doses and high aspect ratios due to the increased significance of material deposition at these conditions. We also demonstrate the suitability of FIB-milled nanochannels for micro/nanofluidic applications
Discovery and Analysis of Evolutionarily Conserved Intronic Splicing Regulatory Elements
Knowledge of the functional cis-regulatory elements that regulate constitutive and alternative pre-mRNA splicing is fundamental for biology and medicine. Here we undertook a genome-wide comparative genomics approach using available mammalian genomes to identify conserved intronic splicing regulatory elements (ISREs). Our approach yielded 314 ISREs, and insertions of ~70 ISREs between competing splice sites demonstrated that 84% of ISREs altered 5ā² and 94% altered 3ā² splice site choice in human cells. Consistent with our experiments, comparisons of ISREs to known splicing regulatory elements revealed that 40%ā45% of ISREs might have dual roles as exonic splicing silencers. Supporting a role for ISREs in alternative splicing, we found that 30%ā50% of ISREs were enriched near alternatively spliced (AS) exons, and included almost all known binding sites of tissue-specific alternative splicing factors. Further, we observed that genes harboring ISRE-proximal exons have biases for tissue expression and molecular functions that are ISRE-specific. Finally, we discovered that for Nova1, neuronal PTB, hnRNP C, and FOX1, the most frequently occurring ISRE proximal to an alternative conserved exon in the splicing factor strongly resembled its own known RNA binding site, suggesting a novel application of ISRE density and the propensity for splicing factors to auto-regulate to associate RNA binding sites to splicing factors. Our results demonstrate that ISREs are crucial building blocks in understanding general and tissue-specific AS regulation and the biological pathways and functions regulated by these AS events
Antireflection silicon structures with hydrophobic property fabricated by three-beam laser interference
This paper demonstrates antireflective structures on silicon wafer surfaces with hydrophobic property fabricated by three-beam laser interference. In this work, a three-beam laser interference system was set up to generate periodic micro-nano hole structures with hexagonal distributions. Compared with the existing technologies, the array of hexagonally-distributed hole structures fabricated by three-beam laser interference reveals a design guideline to achieve considerably low solar-weighted reflectance (SWR) in the wavelength range of 300-780 nm. The resulting periodic hexagonally-distributed hole structures have shown extremely low SWR (1.86%) and relatively large contact angle (140Ā°) providing with a self-cleaning capability on the solar cell surface
Contribution of Knowledge on Breastfeeding Among Mothers Who Joined Mother Support Group Program
The infant feeding decision is complex and involves the influence of psychological, social, and economic factors, and health care system. This study aimed to determine the contribution of knowledge on breastfeeding among nonworking mothers. This was a cross-sectional study conducted in Yogyakarta, Indonesia. A total of 173 nonworking mothers with babies between 0-6 months who joined the mother support group (MSG) program participated in this study. The results showed that knowledge has significant influence on breastfeeding practice among the non working mothers (beta= .21, p= .01). MSG may be a suitable method to promote breastfeeding among Indonesian mothers
Intersite coupling effects in a Kondo lattice
The La dilution of the Kondo lattice CeCoIn_5 is studied. The scaling laws
found for the magnetic susceptibility and the specific heat reveal two
well-separated energy scales, corresponding to the single impurity Kondo
temperature T_K and an intersite spin-liquid temperature T^*. The Ce-dilute
alloy has the expected Fermi liquid ground state, while the specific heat and
resistivity in the dense Kondo regime exhibit non-Fermi-liquid behavior, which
scales with T^*. These observations indicate that the screening of the magnetic
moments in the lattice involves antiferromagnetic intersite correlations with a
larger energy scale in comparison with the Kondo impurity case.Comment: 4 pages, 4 figure
- ā¦