A fast and reliable method for the delineation of tree crown outlines for the computation of crown openness values and other crown parameters

Numerous crown parameters (e.g., leaf area index, diameter, height, volume) can be obtained via the analysis of tree crown photographs. In all cases, parameter values are functions of the position of the crown outline. However, no standardized method to delineate crowns exists. To explore the effect of different outlines on tree crown descriptors, in this case crown openness (CO), and facilitate the adoption of a standard method free of user bias, we developed the program Crown Delineator that automatically delineates any outline around tree crowns following predetermined sensibility settings. We used different outlines to analyze tree CO in contrasting settings: using saplings from four species in young boreal mixedwood forests and medium-sized hybrid poplar trees from a low-density plantation. In both cases, the estimated CO increases when calculated from a looser outline, which had a strong influence on understory available light simulations using a forest simulator. These results demonstrate that the method used to trace crown outlines is an important step in the determination of CO values. We provide a much-needed computer-assisted solution to help standardize this procedure, which can also be used in many other situations in which the delineation of tree crowns is needed (e.g., competition and crown shyness)

The Impact of Simulation Sequencing on Perceived Clinical Decision Making

An emerging nursing education trend is to utilize simulated learning experiences as a means to optimize competency and decision making skills. The purpose of this study was to examine differences in students\u27 perception of clinical decision making and clinical decision making-related self-confidence and anxiety based on the sequence (order) in which they participated in a block of simulated versus hospital-based learning experiences. A quasi-experimental crossover design was used. Between and within group differences were found relative to self-confidence with the decision making process. When comparing groups, at baseline the simulation followed by hospital group had significantly higher self-confidence scores, however, at 14-weeks both groups were not significantly different. Significant within group differences were found in the simulation followed by hospital group only, demonstrating a significant decrease in clinical decision making related anxiety across the semester. Finally, there were no significant difference in; perceived clinical decision making within or between the groups at the two measurement points. Preliminary findings suggest that simulated learning experiences can be offered with alternating sequences without impacting the process, anxiety or confidence with clinical decision making. This study provides beginning evidence to guide curriculum development and allow flexibility based on student needs and available resources

Synthesis and Investigation of the Liquid Crystalline Properties of Polycyclic Aromatic Hydrocarbons

In this thesis, the synthesis and liquid crystalline properties of a series of novel substituted dibenz[a,c]anthracenes is reported. Specifically, a series of hexaalkoxydibenz[a,c]anthracenes were prepared and found not to exhibit a mesophase. In contrast, when substituents are introduced on the aromatic core, columnar mesophases are observed over broad temperature ranges. A series substituted derivatives was prepared and their mesomorphic properties compared. In general, electron-withdrawing substituents promote broad mesophase temperature ranges, as do larger substituents. The liquid crystalline phase is a result of the electronic effects, size and shape of the substituents in the 10 and 13 positions. We also synthesized a series of discotic compounds based on substituted dibenzo[a,c]tetracenedione, dibenzo[a,c]pentacenedione and tetrabenze[a,c,d,f]pentacenedione, with 4, 4 and 8 aliphatic side chains, respectively, using similar methodologies to that of the dibenz[a,c]anthracene compound. These compounds were also found to exhibit columnar mesophases. The mesophase temperature range suggests that the larger aromatic core stabilizes both the crystalline and liquid crystalline phases. The dione functional groups also give a synthetic handle for further synthetic modifications to probe the structure-property relationships of these PAHs

Synthesis of Metal-Containing Polymers and Stable Organic Radical-Containing Polymers and Their Use as Advanced Functional Materials

The work presented in this thesis details the synthesis and characterization of two different families of multifunctional polymers. The first family involved the incorporation of stable 6-oxoverdazyl radicals into polymer scaffolds. This was originally achieved by the polymerization of the radical precursors, phenyl- and isopropyl-6-oxotetrazanes, followed by post-polymerization oxidation to afford the phenyl- and isopropyl-6-oxoverdazyl polymers. A second methodology involved the direct polymerization of isopropyl-6-oxoverdazyl radicals using ring-opening metathesis polymerization (ROMP) to afford polymers with controlled molecular weights and narrow molecular weight distributions. The polymers were characterized by the close comparison of the physical and spectroscopic properties to related model compounds. The semiconducting behaviour of the latter polymer was explored and ultimately exploited in flash memory devices. The second family included redox-active Ni(II) complexes of Goedken’s macrocycle. This macrocycle was incorporated into main-chain polymers via a step growth mechanism involving Sonogashira cross-coupling with π-conjugated solubilizing organic spacers and into side-chain polymers via a chain growth polymerization using ROMP. The resulting polymers spectroscopic and physical properties were characterized and compared to a variety of model compounds. Main-chain Ni(II) complexes of Goedken’s macrocycle and fluorene copolymers were further functionalized with Co2(CO)8 via the alkyne synthetic handle to yielded heterobimetallic copolymers that yielded metal-rich nanomaterials upon pyrolysis in a reducing atmosphere. Combined, this work represents a significant advance in the synthesis, characterization and application of synthetic multifunctional polymers

Validity of the Adiabatic Approximation

We analyze the validity of the adiabatic approximation, and in particular the reliability of what has been called the "standard criterion" for validity of this approximation. Recently, this criterion has been found to be insufficient. We will argue that the criterion is sufficient only when it agrees with the intuitive notion of slowness of evolution of the Hamiltonian. However, it can be insufficient in cases where the Hamiltonian varies rapidly but only by a small amount. We also emphasize the distinction between the adiabatic {\em theorem} and the adiabatic {\em approximation}, two quite different although closely related ideas.Comment: 4 pages, 1 figur

A new perturbative approach to the adiabatic approximation

A new and intuitive perturbative approach to time-dependent quantum mechanics problems is presented, which is useful in situations where the evolution of the Hamiltonian is slow. The state of a system which starts in an instantaneous eigenstate of the initial Hamiltonian is written as a power series which has a straightforward diagrammatic representation. Each term of the series corresponds to a sequence of "adiabatic" evolutions, during which the system remains in an instantaneous eigenstate of the Hamiltonian, punctuated by transitions from one state to another. The first term of this series is the standard adiabatic evolution, the next is the well-known first correction to it, and subsequent terms can be written down essentially by inspection. Although the final result is perhaps not terribly surprising, it seems to be not widely known, and the interpretation is new, as far as we know. Application of the method to the adiabatic approximation is given, and some discussion of the validity of this approximation is presented.Comment: 9 pages. Added references, discussion of previous results, expanded upon discussion of main result and application of i

Sonic levitation apparatus

A sonic levitation apparatus is disclosed which includes a sonic transducer which generates acoustical energy responsive to the level of an electrical amplifier. A duct communicates with an acoustical chamber to deliver an oscillatory motion of air to a plenum section which contains a collimated hole structure having a plurality of parallel orifices. The collimated hole structure converts the motion of the air to a pulsed. Unidirectional stream providing enough force to levitate a material specimen. Particular application to the production of microballoons in low gravity environment is discussed

Synthesis, Characterization, and Pre-Ceramic Properties of π-Conjugated Polymers Based on Ni(II) Complexes of Goedken’s Macrocycle

Nickel(II) complexes of Goedken’s macrocycle bearing alkyne substituents were copolymerized with 2,7-dibromo-9,9-dihexylfluorene, 2,5-dibromo-3-hexylthiophene, and 1,4-dibromo-2,5-bis(hexyloxy)benzene via microwave-induced Sonogashira cross-coupling reactions to produce copolymers 6F, 6T, and 6B. The spectroscopic and electrochemical properties of the copolymers were examined and compared to model compounds. Specifically, each polymer exhibited a nickel-based absorption centered at ca. 589 nm and two π → π* transitions between 272 and 387 nm. While the copolymers did not exhibit extended π conjugation, the nature of the organic spacer did affect the high energy transitions. Furthermore, each copolymer underwent two ligand-based one-electron oxidations at potentials of ca. 0.24 V and ca. 0.75 V relative to the ferrocene/ferrocenium redox couple. Post-polymerization functionalization of the alkyne group in 6F with Co2(CO)8 afforded a novel heterobimetallic copolymer that yielded amorphous nanomaterials containing Ni/Co when pyrolyzed at 800 °C for 3 h under an atmosphere of N2/H2 (95:5)

On the uncertainty of real estate price predictions

Uncertainty quantification associated with real estate appraisal has largely been overlooked in the literature. In this paper, we address this gap by analyzing the uncertainty in automated property valuations using conformal prediction, a distribution-free procedure for constructing prediction intervals with valid coverage in finite samples. Through an empirical study of property prices in the San Francisco Bay Area, we find that prediction intervals obtained using conformal quantile regression have exact coverage. In contrast, prediction intervals obtained from nonconformal quantile regressions severely undercover the data. Furthermore, we show that the intervals adapt to various characteristics of the dwellings, which is crucial given the heterogeneous nature of real estate data. Indeed, we observe that larger and older properties, those in both low and high-income neighborhoods, as well as those on the market for less than one year are more challenging to evaluate.info:eu-repo/semantics/publishedVersio

Injection drug use, HIV/HCV, and related services in nonurban areas of the United States: A systematic review

Background—Injection drug use (IDU) in nonurban areas of the United States is a growing public health concern, but there has been no comprehensive assessment of existing research on injection-related HIV and hepatitis C (HCV) in nonurban communities. We conducted a systematic review to assess the current literature and identify knowledge gaps. Methods—We systematically searched six databases for relevant articles published between January 1990 and June 2016 and screened, extracted, and analyzed the resulting data. Studies were included if they reported original findings from the nonurban U.S. related to 1) IDU and its role in HIV/HCV transmission, and/or 2) HIV/HCV services for people who inject drugs (PWID). Results—Of 2,330 studies, 34 from 24 unique research projects in 17 states met inclusion criteria. Despite increasing HCV and high vulnerability to injection-related HIV outbreaks in nonurban areas, only three studies since 2010 recruited and tested PWID for HIV/HCV. Twelve reported on sharing injection equipment but used varying definitions of sharing, and only eight examined correlates of injection risk. Nine studies on syringe access suggest limited access through syringe exchange programs and pharmacies. Only two studies addressed HCV testing, none addressed HIV testing, and three examined behavioral or other interventions. Conclusions—Despite growing concern regarding nonurban IDU there are few studies of HIV/HCV and related services for PWID, and the existing literature covers a very limited geographical area. Current research provides minimal insights into any unique factors that influence injection risk and HIV/HCV service provision and utilization among nonurban PWID