Matching Items (44)
Description
Lonsdaleite, also called hexagonal diamond, has been widely used as a marker of asteroidal impacts. It is thought to play a central role during the graphite-to-diamond transformation, and calculations suggest that it possesses mechanical properties superior to diamond. However, despite extensive efforts, lonsdaleite has never been produced or described as a separate, pure material. Here we show that defects in cubic diamond provide an explanation for the characteristic d-spacings and reflections reported for lonsdaleite. Ultrahigh-resolution electron microscope images demonstrate that samples displaying features attributed to lonsdaleite consist of cubic diamond dominated by extensive {113} twins and {111} stacking faults. These defects give rise to nanometre-scale structural complexity. Our findings question the existence of lonsdaleite and point to the need for re-evaluating the interpretations of many lonsdaleite-related fundamental and applied studies.
ContributorsNemeth, Peter (Author) / Garvie, Laurence (Author) / Aoki, Toshihiro (Author) / Dubrovinskaia, Natalia (Author) / Dubrovinsky, Leonid (Author) / Buseck, Peter (Author) / Department of Chemistry and Biochemistry (Contributor) / College of Liberal Arts and Sciences (Contributor) / School of Earth and Space Exploration (Contributor) / Center for Meteorite Studies (Contributor) / Ira A. Fulton Schools of Engineering (Contributor) / LeRoy Eyring Center for Solid State Science (Contributor) / School of Molecular Sciences (Contributor)
Created2014-11-01
Description
The relative importance of adaptation and individual ontogenetic experience in dogs' high levels of behavioral compatibility with humans has been a topic of intense scientific attention over the past two decades. Salomons et al. Current Biology, 31, 3137-3144, (2021) recently presented a particularly rich data set of observations on both wolf and dog puppies that has the potential to contribute substantially to this debate. In their study subjecting wolf and dog puppies to batteries of tests, including the ability to follow human pointing gestures, Salomons et al. (2021) reported that dogs, but not wolves, have a specialized innate capacity for cooperation with humans. However, upon reanalyzing this data set, we reach a different conclusion-namely, that when controlling adequately for various environmental factors, wolves and dogs perform similarly in their cooperation with humans.
ContributorsHansen Wheat, Christina (Author) / Van Der Bijl, Wouter (Author) / Wynne, Clive D. L. (Author)
Created2022-09-07
Description
Journal article.
ContributorsProtopopova, Alexandra (Author) / Gilmour, Amanda (Author) / Weiss, Rebecca (Author) / Shen, Jacqueline (Author) / Wynne, Clive D. L. (Author)
Created2012
Description
Journal article.
ContributorsHall, Nathan J. (Author) / Protopopova, Alexandra (Author) / Wynne, Clive D. L. (Author)
Created2014
Description
Journal article.
ContributorsHall, Nathan J. (Author) / Smith, David (College student) (Author) / Wynne, Clive D. L. (Author)
Created2013
ContributorsHall, Nathan J. (Author) / Lord, Kathryn (Author) / Arnold, Anne-Marie (Author) / Wynne, Clive D. L. (Author)
Created2015
ContributorsProtopopova, Alexandra (Author) / Wynne, Clive D. L. (Author)
Created2014-08-01
Description
This dissertation examines dog training in the United States to see how it is implemented and practiced and the potential ramifications for our pet dogs. In Chapter 2, word-based analysis compared the words practicing dog trainers use to describe their work and examined how gender and experience differ between methodologies. Given both the vast history of dog training and the variety of training information available to dog owners, in Chapter 3, I surveyed undergraduate students to determine where dog guardians obtain their information and how they might tackle dog problem behavior. Of 100 practicing dog trainers, only 20%, mostly female trainers using non-aversive methods, were certified. When asked who they asked for dog training advice, most dog guardians reached out to friends, family, or online sources and only about 20% ever attended a formal dog training class.
In Chapter 4, dogs were walked on four different types of leash walking equipment which were attached to a strain gauge to assess if these equipment were any better or worse at reducing a dog’s pulling force; dogs pulled most on a martingale collar and there were no statistically significant differences among the other equipment types to each other. Through behavior analysis, none of the dogs in our study showed impaired welfare.
In Chapter 5, I compared e-collar training to non-aversive methods in the ability to stop chasing of a lure. Dogs experiencing e-collar stimulation were successful in stopping chase of the lure both during training sessions and in testing. None of the dogs in either non-aversive group was successful in the tests. The findings did not indicate that dogs in the e-collar group, or the non-aversive groups, differed in welfare.
As in Chapter 4, despite the lack of immediate negative welfare effects for the dogs experiencing aversive methods like the e-collar, given the demonstrated evidence for Chapters 2 and 3 that individuals who use these aversive tools, either practicing trainers or the general public, may lack the foundation to properly implement them, I recommend caution in their public sale and do not advocate for their use.
ContributorsJohnson, Anamarie Clare (Author) / Wynne, Clive D. L. (Thesis advisor) / Sanabria, Federico (Committee member) / Udell, Monique A. R. (Committee member) / Stenhoff, Donald (Committee member) / Arizona State University (Publisher)
Created2024
Description
Optoelectronic and microelectronic applications of germanium-based materials have received considerable research interest in recent years. A novel method for Ge on Si heteroepitaxy required for such applications was developed via molecular epitaxy of Ge5H12. Next, As(GeH3)3, As(SiH3)3, SbD3, S(GeH3)2 and S(SiH3)2 molecular sources were utilized in degenerate n-type doping of Ge. The epitaxial Ge films produced in this work incorporate donor atoms at concentrations above the thermodynamic equilibrium limits. The donors are nearly fully activated, and led to films with lowest resistivity values thus far reported.
Band engineering of Ge was achieved by alloying with Sn. Epitaxy of the alloy layers was conducted on virtual Ge substrates, and made use of the germanium hydrides Ge2H6 and Ge3H8, and the Sn source SnD4. These films exhibit stronger emission than equivalent material deposited directly on Si, and the contributions from the direct and indirect edges can be separated. The indirect-direct crossover composition for Ge1-ySny alloys was determined by photoluminescence (PL). By n-type doping of the Ge1-ySny alloys via P(GeH3)3, P(SiH3)3 and As(SiH3)3, it was possible to enhance photoexcited emission by more than an order-of-magnitude.
The above techniques for deposition of direct gap Ge1-ySny alloys and doping of Ge were combined with p-type doping methods for Ge1-ySny using B2H6 to fabricate pin heterostructure diodes with active layer compositions up to y=0.137. These represent the first direct gap light emitting diodes made from group IV materials. The effect of the single defected n-i¬ interface in a n-Ge/i-Ge1-ySny/p-Ge1-zSnz architecture on electroluminescence (EL) was studied. This led to lattice engineering of the n-type contact layer to produce diodes of n-Ge1-xSnx/i-Ge1-ySny/p-Ge1-zSnz architecture which are devoid of interface defects and therefore exhibit more efficient EL than the previous design. Finally, n-Ge1-ySny/p-Ge1-zSnz pn junction devices were synthesized with varying composition and doping parameters to investigate the effect of these properties on EL.
Band engineering of Ge was achieved by alloying with Sn. Epitaxy of the alloy layers was conducted on virtual Ge substrates, and made use of the germanium hydrides Ge2H6 and Ge3H8, and the Sn source SnD4. These films exhibit stronger emission than equivalent material deposited directly on Si, and the contributions from the direct and indirect edges can be separated. The indirect-direct crossover composition for Ge1-ySny alloys was determined by photoluminescence (PL). By n-type doping of the Ge1-ySny alloys via P(GeH3)3, P(SiH3)3 and As(SiH3)3, it was possible to enhance photoexcited emission by more than an order-of-magnitude.
The above techniques for deposition of direct gap Ge1-ySny alloys and doping of Ge were combined with p-type doping methods for Ge1-ySny using B2H6 to fabricate pin heterostructure diodes with active layer compositions up to y=0.137. These represent the first direct gap light emitting diodes made from group IV materials. The effect of the single defected n-i¬ interface in a n-Ge/i-Ge1-ySny/p-Ge1-zSnz architecture on electroluminescence (EL) was studied. This led to lattice engineering of the n-type contact layer to produce diodes of n-Ge1-xSnx/i-Ge1-ySny/p-Ge1-zSnz architecture which are devoid of interface defects and therefore exhibit more efficient EL than the previous design. Finally, n-Ge1-ySny/p-Ge1-zSnz pn junction devices were synthesized with varying composition and doping parameters to investigate the effect of these properties on EL.
ContributorsSenaratne, Charutha Lasitha (Author) / Kouvetakis, John (Thesis advisor) / Chizmeshya, Andrew (Committee member) / Menéndez, Jose (Committee member) / Arizona State University (Publisher)
Created2016
Description
Each year, nearly three million dogs will enter one of over 13,000 animal shelters in the United States. The purpose of this dissertation is to better understand how breed identity and dog welfare in the shelter, in addition to post-adoption and fostering interventions out of the shelter, can contribute to the betterment of dog lives. In Chapter 2, I conducted the largest sampling of shelter dogs’ breed identities to-date to determine their breed heritage and compare shelter breed assignment by staff as determined by visual appearance to that of genetic testing. In Chapter 4, I examined the efficacy of a post-adoption intervention intended to reduce returns by encouraging physical activity between adopters and their dogs. In Chapter 6, I examined the effects of brief stays in a foster home on the urinary cortisol: creatinine ratios of dogs awaiting adoption compared to ratios collected before or after their stays; and in Chapter 7, I characterized the relationships between multiple physiological, health, and cognitive measures and the in-kennel behavior of shelter dogs.
Four suggestions from the findings of this dissertation that will likely better the lives of dogs living in animal shelters are: 1) Shelter dog breed heritage is complex and visually identifying multiple breeds in a mixed breed dog is difficult at best. Shelters should instead focus on communicating the morphology and behavior of the dogs in their care to best support adopters. 2) While encouraging walking did not influence owner behavior, adopters who reported higher obligation and self-efficacy in dog walking were more active with their dogs. Thus, post-adoption interventions that can effectively target owner perceptions of obligation and self-efficacy may be more successful in changing behavior. 3) Temporary fostering is an impactful intervention that reduces stress for dogs awaiting adoption; however addressing stressors present at shelters that are likely contributing to higher stress responding is also needed. 4) It is possible to predict the internal stress responding of shelter dogs by observing their overt, in-kennel behavior, and this study is a first step in assessing and improving the welfare of dogs living in animal shelters.
Four suggestions from the findings of this dissertation that will likely better the lives of dogs living in animal shelters are: 1) Shelter dog breed heritage is complex and visually identifying multiple breeds in a mixed breed dog is difficult at best. Shelters should instead focus on communicating the morphology and behavior of the dogs in their care to best support adopters. 2) While encouraging walking did not influence owner behavior, adopters who reported higher obligation and self-efficacy in dog walking were more active with their dogs. Thus, post-adoption interventions that can effectively target owner perceptions of obligation and self-efficacy may be more successful in changing behavior. 3) Temporary fostering is an impactful intervention that reduces stress for dogs awaiting adoption; however addressing stressors present at shelters that are likely contributing to higher stress responding is also needed. 4) It is possible to predict the internal stress responding of shelter dogs by observing their overt, in-kennel behavior, and this study is a first step in assessing and improving the welfare of dogs living in animal shelters.
ContributorsGunter, Lisa (Author) / Wynne, Clive D. L. (Thesis advisor) / Luecken, Linda J. (Committee member) / Barber, Rebecca T. (Committee member) / Casey, Rachel A. (Committee member) / Arizona State University (Publisher)
Created2018