118 research outputs found
Distributions and abundances of Pacific sardine (Sardinops sagax) and other pelagic fishes in the California Current Ecosystem during spring 2006, 2008, and 2010, estimated from acoustic–trawl surveys
The abundances and distributions of coastal pelagic fish
species in the California Current Ecosystem from San Diego to southern Vancouver Island, were estimated from combined acoustic and trawl surveys conducted in the spring of 2006, 2008, and 2010. Pacific sardine (Sardinops sagax), jack mackerel (Trachurus symmetricus), and Pacific mackerel (Scomber japonicus) were the dominant coastal pelagic fish species, in that order. Northern anchovy (Engraulis mordax) and Pacific herring (Clupea pallasii) were sampled only sporadically and therefore estimates for these species were
unreliable. The estimates of sardine biomass compared well with those of the annual assessments and confirmed a declining trajectory of the “northern stock” since 2006. During the sampling period, the biomass of jack mackerel was stable or increasing, and that of Pacific mackerel was
low and variable. The uncertainties in these estimates are mostly the result of spatial patchiness which increased
from sardine to mackerels to anchovy and herring. Future surveys of coastal pelagic fish species in the California
Current Ecosystem should benefit from adaptive sampling based on modeled habitat; increased echosounder and trawl sampling, particularly for the most patchy and nearshore species; and directed-trawl sampling for improved species identification and estimations of their acoustic target
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Investigation of Spiral Bevel Gear Condition Indicator Validation via AC-29-2C Using Fielded Rotorcraft HUMS Data
This report presents the analysis of gear condition indicator data collected on a helicopter when damage occurred in spiral bevel gears. The purpose of the data analysis was to use existing in-service helicopter HUMS flight data from faulted spiral bevel gears as a Case Study, to better understand the differences between HUMS data response in a helicopter and a component test rig, the NASA Glenn Spiral Bevel Gear Fatigue Rig. The reason spiral bevel gear sets were chosen to demonstrate differences in response between both systems was the availability of the helicopter data and the availability of a test rig that was capable of testing spiral bevel gear sets to failure. The objective of the analysis presented in this paper was to re-process helicopter HUMS data with the same analysis techniques applied to the spiral bevel rig test data. The damage modes experienced in the field were mapped to the failure modes created in the test rig. A total of forty helicopters were evaluated. Twenty helicopters, or tails, experienced damage to the spiral bevel gears in the nose gearbox. Vibration based gear condition indicators data was available before and after replacement. The other twenty tails had no known anomalies in the nose gearbox within the time frame of the datasets. These twenty tails were considered the baseline dataset. The HUMS gear condition indicators evaluated included gear condition indicators (CI) Figure of Merit 4 (FM4), Root Mean Square (RMS) or Diagnostic Algorithm 1 (DA1) and +/- 3 Sideband Index (SI3). Three additional condition indicators, not currently calculated on-board, were calculated from the archived data. These three indicators were +/- 1 Sideband Index (SI1), the DA1 of the difference signal (DiffDA1) and the peak-to-peak of the difference signal (DP2P). Results found the CI DP2P, not currently available in the on-board HUMS, performed the best, responding to varying levels of damage on thirteen of the fourteen helicopters evaluated. Two additional CIs also not in the on-board system, DiffDA1and SI1, also performed well responding to twelve and ten of the fourteen helicopters evaluated respectively. Of the three CIs currently available in the MSPU, DA1, FM4 and SI3, SI3, responded to eight, DA1 responded to six and FM4 responded to four of the fourteen helicopters evaluated. FM4, the poorest performing CI, was not as responsive to damage as the other five CIs. Conversely, when compared to the other two, it was the only CI that responded to damage on two helicopters. CI response could not be correlated to specific failure modes due to limited pictures and subjective descriptions found within the TDA. Flight regime did affect CI response to some gear faults. Due to the range of operating conditions for each regime, more studies are required to determine their sensitivity to regimes
SecureMEMS: Selective Deposition of Energetic Materials
There exists a pressing operational need to secure and control access to high-valued electromechanical systems, and in some cases render them inoperable. Developing a reliable method for depositing energetic materials will allow for the near-seamless integration of electromechanical systems and energetic material, and, in turn, provide the pathway for security and selective destruction that is needed. In this work, piezoelectric inkjet printing was used to selectively deposit energetic materials. Nanothermites, comprising of nanoscale aluminum and nanoscale copper oxide suspended in dimethyl-formamide (DMF), were printed onto silicon wafers, which enabled both thermal and thrust measurements of the decomposing energetic material. Various solids loadings were studied in order to optimize printing characteristics. Going forward, further studies will focus on the plausibility of inkjet printing other energetic materials for the purposes of the degradation of electromechanical systems
Prediction and confirmation of seasonal migration of Pacific sardine (Sardinops sagax) in the California Current Ecosystem
During the last century, the population of Pacific sardine
(Sardinops sagax) in the California Current Ecosystem has exhibited large fluctuations in abundance and migration behavior. From approximately 1900 to 1940, the abundance
of sardine reached 3.6 million metric tons and the “northern stock” migrated from offshore of California
in the spring to the coastal areas near Oregon, Washington, and Vancouver Island in the summer. In the 1940s, the sardine stock collapsed and the few remaining sardine schools concentrated in the coastal region off southern California, year-round, for the next 50 years. The stock gradually recovered in the late 1980s and resumed its seasonal migration between regions off southern California and Canada. Recently, a model was developed which predicts
the potential habitat for the northern stock of Pacific sardine and its seasonal dynamics. The habitat predictions were successfully validated using data from sardine surveys
using the daily egg production method; scientific trawl surveys off the Columbia River mouth; and commercial sardine landings off Oregon, Washington, and Vancouver Island. Here, the predictions of the potential habitat and seasonal migration of the northern stock of sardine are
validated using data from “acoustic–trawl” surveys of the entire west coast of the United States during the spring
and summer of 2008. The estimates of sardine biomass and lengths from the two surveys are not significantly
different between spring and summer, indicating that they are representative of the entire stock. The results
also confirm that the model of potential sardine habitat can be used to optimally apply survey effort and thus minimize random and systematic sampling error in the biomass
estimates. Furthermore, the acoustic–trawl survey data are useful to estimate concurrently the distributions and abundances of other pelagic fishes
Self-love and sociability: the ‘rudiments of commerce’ in the state of nature
Istvan Hont’s classic work on the theoretical links between the seventeenth-century natural jurists Hugo Grotius and Samuel Pufendorf and the eighteenth-century Scottish political economists remains a popular trope among intellectual and economic historians of various stamps. Despite this, a common criticism levelled at Hont remains his relative lack of engagement with the relationship between religion and economics in the early modern period. This paper challenges this aspect of Hont’s narrative by drawing attention to an alternative, albeit complementary, assessment of the natural jurisprudential heritage of eighteenth-century British political economy. Specifically, the article attempts to map on to Hont’s thesis the Christian Stoic interpretation of Grotius and Pufendorf which has gained greater currency in recent years. In doing so, the paper argues that Grotius and Pufendorf’s contributions to the ‘unsocial sociability’ debate do not necessarily lead directly to the Scottish school of political economists, as is commonly assumed. Instead, it contends that a reconsideration of Grotius and Pufendorf as neo-Stoic theorists, particularly via scrutiny of their respective adaptations of the traditional Stoic theory of oikeiosis, steers us towards the heart of the early English ‘clerical’ Enlightenment
Macrophage-derived human resistin is induced in multiple helminth infections and promotes inflammatory monocytes and increased parasite burden.
Parasitic helminth infections can be associated with lifelong morbidity such as immune-mediated organ failure. A better understanding of the host immune response to helminths could provide new avenues to promote parasite clearance and/or alleviate infection-associated morbidity. Murine resistin-like molecules (RELM) exhibit pleiotropic functions following helminth infection including modulating the host immune response; however, the relevance of human RELM proteins in helminth infection is unknown. To examine the function of human resistin (hResistin), we utilized transgenic mice expressing the human resistin gene (hRetnTg+). Following infection with the helminth Nippostrongylus brasiliensis (Nb), hResistin expression was significantly upregulated in infected tissue. Compared to control hRetnTg- mice, hRetnTg+ mice suffered from exacerbated Nb-induced inflammation characterized by weight loss and increased infiltration of inflammatory monocytes in the lung, along with elevated Nb egg burdens and delayed parasite expulsion. Genome-wide transcriptional profiling of the infected tissue revealed that hResistin promoted expression of proinflammatory cytokines and genes downstream of toll-like receptor signaling. Moreover, hResistin preferentially bound lung monocytes, and exogenous treatment of mice with recombinant hResistin promoted monocyte recruitment and proinflammatory cytokine expression. In human studies, increased serum resistin was associated with higher parasite load in individuals infected with soil-transmitted helminths or filarial nematode Wuchereria bancrofti, and was positively correlated with proinflammatory cytokines. Together, these studies identify human resistin as a detrimental factor induced by multiple helminth infections, where it promotes proinflammatory cytokines and impedes parasite clearance. Targeting the resistin/proinflammatory cytokine immune axis may provide new diagnostic or treatment strategies for helminth infection and associated immune-mediated pathology
SRGeJ045359.9+622444: A 55-min Period Eclipsing AM CVn Discovered from a Joint SRG/eROSITA + ZTF Search
AM CVn systems are ultra-compact binaries where a white dwarf accretes from a
helium-rich degenerate or semi-degenerate donor. Some AM CVn systems will be
among the loudest sources of gravitational waves for the upcoming Laser
Interferometer Space Antenna (LISA), yet the formation channel of AM CVns
remains uncertain. We report the study and characterisation of a new eclipsing
AM CVn, SRGeJ045359.9+622444 (hereafter SRGeJ0453), discovered from a joint
SRG/eROSITA and ZTF program to identify cataclysmic variables (CVs). We
obtained optical photometry to confirm the eclipse of SRGeJ0453 and determine
the orbital period to be min. We
constrain the binary parameters by modeling the high-speed photometry and
radial velocity curves and find
and . The X-ray spectrum is
approximated by a power-law model with an unusually flat photon index of
previously seen in magnetic CVs with SRG/eROSITA, but verifying
the magnetic nature of SRGeJ0453 requires further investigation. Optical
spectroscopy suggests that the donor star of SRGeJ0453 could have initially
been a He star or a He white dwarf. SRGeJ0453 is the ninth eclipsing AM CVn
system published to date, and its lack of optical outbursts have made it
elusive in previous surveys. The discovery of SRGeJ0453 using joint X-ray and
optical surveys highlights the potential for discovering similar systems in the
near future.Comment: Submitted to Ap
SN 2020jgb: A Peculiar Type Ia Supernova Triggered by a Massive Helium-Shell Detonation in a Star-Forming Galaxy
The detonation of a thin () helium shell
(He-shell) atop a white dwarf (WD) is a promising
mechanism to explain normal Type Ia supernovae (SNe Ia), while thicker
He-shells and less massive WDs may explain some recently observed peculiar SNe
Ia. We present observations of SN 2020jgb, a peculiar SN Ia discovered by the
Zwicky Transient Facility (ZTF). Near maximum light, SN 2020jgb is slightly
subluminous (ZTF -band absolute magnitude between and
mag depending on the amount of host galaxy extinction) and shows an unusually
red color ( between 0.4 and 0.2 mag) due to
strong line-blanketing blueward of 5000 . These properties
resemble those of SN 2018byg, a peculiar SN Ia consistent with a thick He-shell
double detonation (DDet) SN. Using detailed radiative transfer models, we show
that the optical spectroscopic and photometric evolution of SN 2020jgb are
broadly consistent with a (C/O core + He-shell;
up to depending on the total host extinction)
progenitor ignited by a thick () He-shell. We
detect a prominent absorption feature at 1 in the
near-infrared (NIR) spectrum of SN 2020jgb, which could originate from unburnt
helium in the outermost ejecta. While the sample size is limited, similar 1
features have been detected in all the thick He-shell DDet
candidates with NIR spectra obtained to date. SN 2020jgb is also the first
subluminous, thick He-shell DDet SN discovered in a star-forming galaxy,
indisputably showing that He-shell DDet objects occur in both star-forming and
passive galaxies, consistent with the normal SN Ia population.Comment: 23 pages, 10 figures. Updated to accepted version (ApJ
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