3,399 research outputs found
Polyion Detection via Allâsolidâcontact Paperâbased Polyionâsensitive Polymeric Membrane Electrodes
The first allâsolidâcontact paperâbased singleâuse polyionâsensitive ionâselective electrodes (ISEs) are described. These polyionâsensitive ISEs are fabricated using cellulose filter paper coated with a carbon ink conductive layer. A polyanion sensing membrane is cast on a section of the coated paper and the sensor is insulated, resulting in a disposable, singleâuse device. Various polyanions are shown to yield large negative potentiometric responses when using these disposable devices for direct polyanion detection. These new sensors are further demonstrated to be useful in indirect polycation detection when polycations (i.âe., polyquaterniums (PQs)) are titrated with polyanionic dextran sulfate (DS). Titrations monitored using these paperâbased, allâsolidâcontact devices yield endpoints proportional to the given PQ concentration present in the test sample.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151253/1/elan201900155.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151253/2/elan201900155_am.pd
The Stellar Populations and Evolution of Lyman Break Galaxies
Using deep near-IR and optical observations of the HDF-N from the HST NICMOS
and WFPC2 and from the ground, we examine the spectral energy distributions
(SEDs) of Lyman break galaxies (LBGs) at 2.0 < z < 3.5. The UV-to-optical
rest-frame SEDs of the galaxies are much bluer than those of present-day spiral
and elliptical galaxies, and are generally similar to those of local starburst
galaxies with modest amounts of reddening. We use stellar population synthesis
models to study the properties of the stars that dominate the light from LBGs.
Under the assumption that the star-formation rate is continuous or decreasing
with time, the best-fitting models provide a lower bound on the LBG mass
estimates. LBGs with ``L*'' UV luminosities are estimated to have minimum
stellar masses ~ 10^10 solar masses, or roughly 1/10th that of a present-day L*
galaxy. By considering the effects of a second component of maximally-old
stars, we set an upper bound on the stellar masses that is ~ 3-8 times the
minimum estimate. We find only loose constraints on the individual galaxy ages,
extinction, metallicities, initial mass functions, and prior star-formation
histories. We find no galaxies whose SEDs are consistent with young (< 10^8
yr), dust-free objects, which suggests that LBGs are not dominated by ``first
generation'' stars, and that such objects are rare at these redshifts. We also
find that the typical ages for the observed star-formation events are
significantly younger than the time interval covered by this redshift range (~
1.5 Gyr). From this, and from the relative absence of candidates for quiescent,
non-star-forming galaxies at these redshifts in the NICMOS data, we suggest
that star formation in LBGs may be recurrent, with short duty cycles and a
timescale between star-formation events of < 1 Gyr. [Abridged]Comment: LaTeX, 37 pages, 21 figures. Accepted for publication in the
Astrophysical Journa
Information Sharing to Improve Retail Product Freshness of Perishables (ed.3)
We explore the value of information (VOI) in the context of a retailer that provides a
perishable product to consumers and receives replenishment from a single supplier. We assume a
periodic review model with stochastic demand, lost sales, and order quantity restrictions. The
product lifetime is fixed and deterministic once received by the retailer, although the age of
replenished items provided by the supplier varies stochastically over time. Since the product is
perishable, any unsold inventory remaining after the lifetime elapses must be discarded
(outdated). Without the supplier explicitly informing the retailer of the product age, the age
remains unknown until receipt. With information sharing, the retailer is informed of the product
age prior to placing an order and hence can utilize this information in its decisionâmaking. We
formulate the retailerâs replenishment policies, with and without knowing the age of the product
upon receipt, and measure the VOI as the marginal improvement in profit that the retailer
achieves with information sharing, relative to the case when no information is shared. We
establish the importance of information sharing and identify the conditions under which
substantial benefits can be realized
Revenue Management and the Analytics Explosion: Perspectives from Industry Experts
On October 2-3, 2007, the third annual Revenue Management and Price Optimization conference was held at the Georgia Institute of Technology. The conference explored how multiple factors, including fragmentation of customer markets, transparency in markets, and globalization have spurred a transformation from intuition-based to analytical-based decision making across many industries. Panelists included representatives from industries spanning airline, hotel, gaming, grocery, jewelry, package delivery, consumer goods, manufacturing, and consulting. This paper summarizes key discussions that emerged from the conference and highlights success stories portrayed in keynote addresses given by James Whitehurst, former chief operating office of Delta Air Lines; Rick Campana, Vice President of Corporate Marketing of the United Parcel Service; and, Chuck Neville, Executive Director of Finance of General Motors Service and Parts Operations
The Evolution of Early-type Field Galaxies Selected from a NICMOS Map of the Hubble Deep Field North
The redshift distribution of well-defined samples of distant early-type
galaxies offers a means to test the predictions of monolithic and hierarchical
galaxy formation scenarios. NICMOS maps of the entire Hubble Deep Field North
in the F110W and F160W filters, when combined with the available WFPC2 data,
allow us to calculate photometric redshifts and determine the morphological
appearance of galaxies at rest-frame optical wavelengths out to z ~ 2.5. Here
we report results for two subsamples of early-type galaxies, defined primarily
by their morphologies in the F160W band, which were selected from the NICMOS
data down to H160_{AB} < 24.0. The observed redshift distributions of our two
early-type samples do not match that predicted by a monolithic collapse model,
which shows an overabundance at z > 1.5. A hierarchical formation model better
matches the redshift distribution of the HDF-N early-types at z > 1.5, but
still does not adequately describe the observed early-types. The hierarchical
model predicts significantly bluer colors on average than the observed
early-type colors, and underpredicts the observed number of early-types at z <
1. [abridged]Comment: Accepted for publication in the Astronomical Journal; 54 pages, 21
figures. Figures 10 and 11 are included separately in JPEG forma
Returning Students in Engineering Education: Making a Case for âExperience Capitalâ
Students returning to college are not generally studied, where most of the research on non-traditional students is focused on individuals returning to earn their undergraduate degree. There are, however, many students returning to receive graduate degrees as they pursue new directions in life by interest or economic necessity. Undergraduate students with experience have clear educational related goals, practical approaches to problem-solving, and high learning motivation.Returning graduate students are expected to model similar behaviors. These individuals bring a lifetime of personal and professional expertise, which we identify as âexperience capital.âA review of the literature reveals that capital has been pondered since early western philosophers considered the concept of social capital in terms of âcommunity governanceâ. Others credit Dewey with the first use of the term âsocial capitalâ. Since then, development of other capitals include human, cultural, and symbolic. Human capital is viewed as knowledge, skills, and attributes; cultural capital as an indicator of class position acquired by family and education ; and symbolic as the prestige, recognition, and fame. Today, social capital is viewed as the networks,relationships, and connections of influence and support. Experience capital is the partial union of social, human, cultural, and symbolic capital, which individuals develop from their persona land professional experiences as they progress through life.This is an exploratory study capturing the perceptions of âexperience capitalâ of individuals with several years of professional experience in their discipline returning for a doctoral degree in engineering education. The research question this study addresses is: what âexperience capitalâdo returning students bring to an engineering education doctoral program? The participants will be interviewed; open coding will be used to identify common themes. The results of this qualitative study will position the experiences of the participants at the partial union of social,human, cultural, and symbolic capital, in a space called experience capital
High Redshift Galaxies in the Hubble Deep Field. Color Selection and Star Formation History to z=4
The Lyman decrement associated with the cumulative effect of HI in QSO
absorption systems along the line of sight provides a distinctive feature for
identifying galaxies at z>2.5. The Hubble Deep Field (HDF) observations offer
the opportunity to exploit the ubiquitous effect of intergalactic absorption
and obtain useful statistical constraints on the redshift distribution of
galaxies considerably fainter than current spectroscopic limits. We model the
HI cosmic opacity as a function of redshift, including scattering in resonant
lines of the Lyman series and Lyman-continuum absorption, and use stellar
population synthesis models with a wide variety of ages, metallicities, dust
contents, and redshifts, to derive color selection criteria that provide a
robust separation between high redshift and low redshift galaxies. From the HDF
images we construct a sample of star-forming galaxies at 2<z<4.5. While none of
the more than 60 objects in the HDF having known Keck/LRIS spectroscopic
redshifts in the range 0<z<1.4 is found to contaminate our high-redshift
sample, our color criteria are able to efficiently select the 2.6<z<3.2
galaxies identified by Steidel et al. (1996b). The ultraviolet (and blue)
dropout technique opens up the possibility of investigating cosmic star and
element formation in the early universe.Comment: TeX file, 21 pages + 11 figures and 3 tables (postscript), submitted
to MNRA
Bowhead whales use two foraging strategies in response to fine-scale differences in zooplankton vertical distribution
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fortune, S. M. E., Ferguson, S. H., Trites, A. W., Hudson, J. M., & Baumgartner, M. F. Bowhead whales use two foraging strategies in response to fine-scale differences in zooplankton vertical distribution. Scientific Reports, 10(1), (2020): 20249, doi:10.1038/s41598-020-76071-9.As zooplanktivorous predators, bowhead whales (Balaena mysticetus) must routinely locate patches of prey that are energy-rich enough to meet their metabolic needs. However, little is known about how the quality and quantity of prey might influence their feeding behaviours. We addressed this question using a new approach that included: (1) multi-scale biologging and unmanned aerial system observations of bowhead whales in Cumberland Sound, Nunavut (Canada), and (2) an optical plankton counter (OPC) and net collections to identify and enumerate copepod prey species through the water column. The OPC data revealed two prey layers comprised almost exclusively of lipid-rich calanoid copepods. The deep layer contained fewer, but larger, particles (10% greater overall biomass) than the shallow prey layer. Dive data indicated that the whales conducted long deep Square-shaped dives (80% of dives; averaging depth of 260.4 m) and short shallow Square-shaped dives (16%; averaging depth of 22.5 m) to feed. The whales tended to dive proportionally more to the greater biomass of zooplankton that occurred at depth. Combining behavioural recordings with prey sampling showed a more complex feeding ecology than previously understood, and provides a means to evaluate the energetic balance of individuals under current environmental conditions.Funding was awarded to S.H.F and provided by: Fisheries and Oceans Canada (Emerging Fisheries), World Wildlife Fund Canada (Arctic Species Conservation Fund), Nunavut Wildlife Research Trust Fund, Nunavut General Monitoring Program, Ocean Tracking Network and ArcticNet Centre of Excellence. Personal support was awarded to S.M.E.F and provided by Natural Sciences and Engineering Research Council Canadian Graduate Scholarship, Northern Scientific Training Program (Canadian Polar Commission), The Molson Foundation and the W.Garfield Weston Foundation
Appendix to "Relicensing Fees as a Secondary Market Strategy"
Appendix to "Relicensing Fees as a Secondary Market Strategy
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