113 research outputs found
A Comparison of VNIR and MIR Spectroscopy for Predicting Various Soil Properties
Soil plays an important role in our daily lives, namely producing food, cleaning water and storing carbon. The ability to rapidly and cost-effectively quantify the various components of soils can help us understand and better manage this important resource. This study aims to compare the ability of visible near-infrared (VNIR) spectroscopy and mid-infrared (MIR) spectroscopy to quickly and accurately predict various important soil properties (electrical conductivity, soil pH, cation exchange capacity, exchangeable cations, phosphorus, carbon, beta-glucosidase enzyme activity and nitrogen). Prediction models were developed using partial least squares regression (PLSR) techniques. Three different calibration sampling methods were tested along with various spectral preprocessing techniques to find the best predictive ability of VNIR and MIR. Soil components related to carbon, nitrogen, and cation exchange capacity had good predictive ability (R2 \u3e 0.8) by both VNIR and MIR, but MIR was more accurate. Electrical conductivity, sodium cations, and phosphorus were poorly predicted by both (\u3c0.71). VNIR models were not as robust as MIR models but could be potentially useful for qualitative analyses when rapid analyses are preferred over methods are more accurate. MIR predictions overall yielded more accurate predictions than VNIR and could potentially be used as a surrogate method for timely laboratory techniques for spectrally active soil components.
Advisor: Paul Hanso
Vision-Based Close Formation Flight of Unmanned Aerial Vehicles (UAVs)
Since cost of unmanned aircraft vehicles have decreased recently due to technological advancement, there has been a growing interest in developing and implementing systems for close formation missions. Our research objective is to investigate and implement low-cost vision-based tracking algorithms for such a flight formation. For the first technical objective (TO), we are developing an algorithm for vision-based tracking using a Raspberry-Pi hardware. For the second TO, we assembled a quadcopter to be equipped with a camera module and a calibrated flight control computer. In addition, the research team has performed flight testing to obtain video data of a flying marked quadcopter as a reference for developing the tracking algorithm. The final TO is to test-fly two quadcopters in close formation using vision-based tracking algorithm. Ultimately, this research will provide a reliable platform to further investigate formation flight capabilities, and to extrapolate the technology to a wide range of applications
Cp*Fe(Me2PCH2CH2PMe2)(CHO) : hydride shuttle reactivity of a thermally stable formyl complex.
[Cp*Fe(Me2PCH2CH2PMe2)(CO)]+ [BArF24]− has been synthesised and characterised using single crystal X-ray diffraction, NMR and IR spectroscopies. Reduction of the CO ligand using Na[Et3BH] produces the corresponding neutral formyl complex Cp*Fe(Me2PCH2CH2PMe2)(CHO), that is very thermally stable, and which is attributed to the electron-releasing properties of the spectator ligands. This compound is a potent hydride donor which exists in equilibrium with [Et3BH]−, Et3B, and the structural isomer (η4-C5Me5H)Cp*Fe(Me2PCH2CH2PMe2)(CO), resulting from reversible hydride migration to the Cp* ligand
Medication use, renin-angiotensin system inhibitors, and acute care utilization after hospitalization in patients with chronic kidney disease.
OBJECTIVES: The aims of this secondary analysis were to: (a) characterize medication use following hospital discharge for patients with chronic kidney disease (CKD), and (b) investigate relationships of medication use with the primary composite outcome of acute care utilization 90 days after hospitalization.
METHODS: The CKD-Medication Intervention Trial (CKD-MIT) enrolled acutely ill hospitalized patients with CKD stages 3-5 not dialyzed (CKD 3-5 ND). In this post hoc analysis, data for medication use were characterized, and the relationship of medication use with the primary outcome was evaluated using Cox proportional hazards models.
RESULTS: Participants were taking a mean of 12.6 (standard deviation=5.1) medications, including medications from a wide variety of medication classes. Nearly half of study participants were taking angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARB). ACE inhibitor/ARB use was associated with decreased risk of the primary outcome (hazard ratio=0.51; 95% confidence interval 0.28-0.95;
CONCLUSIONS: A large number, variety, and complexity of medications were used by hospitalized patients with CKD 3-5 ND. ACE inhibitor or ARB use at hospital discharge was associated with a decreased risk of 90-day acute care utilization
Analysis of Neptune's 2017 Bright Equatorial Storm
We report the discovery of a large (8500 km diameter) infrared-bright
storm at Neptune's equator in June 2017. We tracked the storm over a period of
7 months with high-cadence infrared snapshot imaging, carried out on 14 nights
at the 10 meter Keck II telescope and 17 nights at the Shane 120 inch reflector
at Lick Observatory. The cloud feature was larger and more persistent than any
equatorial clouds seen before on Neptune, remaining intermittently active from
at least 10 June to 31 December 2017. Our Keck and Lick observations were
augmented by very high-cadence images from the amateur community, which
permitted the determination of accurate drift rates for the cloud feature. Its
zonal drift speed was variable from 10 June to at least 25 July, but remained a
constant m s from 30 September until at least 15
November. The pressure of the cloud top was determined from radiative transfer
calculations to be 0.3-0.6 bar; this value remained constant over the course of
the observations. Multiple cloud break-up events, in which a bright cloud band
wrapped around Neptune's equator, were observed over the course of our
observations. No "dark spot" vortices were seen near the equator in HST imaging
on 6 and 7 October. The size and pressure of the storm are consistent with
moist convection or a planetary-scale wave as the energy source of convective
upwelling, but more modeling is required to determine the driver of this
equatorial disturbance as well as the triggers for and dynamics of the observed
cloud break-up events.Comment: 42 pages, 14 figures, 6 tables; Accepted to Icaru
Evidence Supporting a Zoonotic Origin of Human Coronavirus Strain NL63
The relationship between bats and coronaviruses (CoVs) has received considerable attention since the severe acute respiratory syndrome (SARS)-like CoV was identified in the Chinese horseshoe bat (Rhinolophidae) in 2005. Since then, several bats throughout the world have been shown to shed CoV sequences, and presumably CoVs, in the feces; however, no bat CoVs have been isolated from nature. Moreover, there are very few bat cell lines or reagents available for investigating CoV replication in bat cells or for isolating bat CoVs adapted to specific bat species. Here, we show by molecular clock analysis that alphacoronavirus (α-CoV) sequences derived from the North American tricolored bat (Perimyotis subflavus) are predicted to share common ancestry with human CoV (HCoV)-NL63, with the most recent common ancestor between these viruses occurring approximately 563 to 822 years ago. Further, we developed immortalized bat cell lines from the lungs of this bat species to determine if these cells were capable of supporting infection with HCoVs. While SARS-CoV, mouse-adapted SARS-CoV (MA15), and chimeric SARS-CoVs bearing the spike genes of early human strains replicated inefficiently, HCoV-NL63 replicated for multiple passages in the immortalized lung cells from this bat species. These observations support the hypothesis that human CoVs are capable of establishing zoonotic-reverse zoonotic transmission cycles that may allow some CoVs to readily circulate and exchange genetic material between strains found in bats and other mammals, including humans
Improved Standardization of Type II-P Supernovae: Application to an Expanded Sample
In the epoch of precise and accurate cosmology, cross-confirmation using a
variety of cosmographic methods is paramount to circumvent systematic
uncertainties. Owing to progenitor histories and explosion physics differing
from those of Type Ia SNe (SNe Ia), Type II-plateau supernovae (SNe II-P) are
unlikely to be affected by evolution in the same way. Based on a new analysis
of 17 SNe II-P, and on an improved methodology, we find that SNe II-P are good
standardizable candles, almost comparable to SNe Ia. We derive a tight Hubble
diagram with a dispersion of 10% in distance, using the simple correlation
between luminosity and photospheric velocity introduced by Hamuy & Pinto 2002.
We show that the descendent method of Nugent et al. 2006 can be further
simplified and that the correction for dust extinction has low statistical
impact. We find that our SN sample favors, on average, a very steep dust law
with total to selective extinction R_V<2. Such an extinction law has been
recently inferred for many SNe Ia. Our results indicate that a distance
measurement can be obtained with a single spectrum of a SN II-P during the
plateau phase combined with sparse photometric measurements.Comment: ApJ accepted version. Minor change
From polyps to pixels: understanding coral reef resilience to local and global change across scales
Abstract Context Coral reef resilience is the product of multiple interacting processes that occur across various interacting scales. This complexity presents challenges for identifying solutions to the ongoing worldwide decline of coral reef ecosystems that are threatened by both local and global human stressors. Objectives We highlight how coral reef resilience is studied at spatial, temporal, and functional scales, and explore emerging technologies that are bringing new insights to our understanding of reef resilience. We then provide a framework for integrating insights across scales by using new and existing technological and analytical tools. We also discuss the implications of scale on both the ecological processes that lead to declines of reefs, and how we study those mechanisms. Methods To illustrate, we present a case study from Kāneʻohe Bay, Hawaiʻi, USA, linking remotely sensed hyperspectral imagery to within-colony symbiont communities that show differential responses to stress. Results In doing so, we transform the scale at which we can study coral resilience from a few individuals to entire ecosystems. Conclusions Together, these perspectives guide best practices for designing management solutions that scale from individuals to ecosystems by integrating multiple levels of biological organization from cellular processes to global patterns of coral degradation and resilience
Berkeley Supernova Ia Program I: Observations, Data Reduction, and Spectroscopic Sample of 582 Low-Redshift Type Ia Supernovae
In this first paper in a series we present 1298 low-redshift (z\leq0.2)
optical spectra of 582 Type Ia supernovae (SNe Ia) observed from 1989 through
2008 as part of the Berkeley SN Ia Program (BSNIP). 584 spectra of 199 SNe Ia
have well-calibrated light curves with measured distance moduli, and many of
the spectra have been corrected for host-galaxy contamination. Most of the data
were obtained using the Kast double spectrograph mounted on the Shane 3 m
telescope at Lick Observatory and have a typical wavelength range of
3300-10,400 Ang., roughly twice as wide as spectra from most previously
published datasets. We present our observing and reduction procedures, and we
describe the resulting SN Database (SNDB), which will be an online, public,
searchable database containing all of our fully reduced spectra and companion
photometry. In addition, we discuss our spectral classification scheme (using
the SuperNova IDentification code, SNID; Blondin & Tonry 2007), utilising our
newly constructed set of SNID spectral templates. These templates allow us to
accurately classify our entire dataset, and by doing so we are able to
reclassify a handful of objects as bona fide SNe Ia and a few other objects as
members of some of the peculiar SN Ia subtypes. In fact, our dataset includes
spectra of nearly 90 spectroscopically peculiar SNe Ia. We also present
spectroscopic host-galaxy redshifts of some SNe Ia where these values were
previously unknown. [Abridged]Comment: 34 pages, 11 figures, 11 tables, revised version, re-submitted to
MNRAS. Spectra will be released in January 2013. The SN Database homepage
(http://hercules.berkeley.edu/database/index_public.html) contains the full
tables, plots of all spectra, and our new SNID template
- …