Influence of Laser Processing Parameters on the Corrosion Behavior in 316L Stainless Steel Laser Powder Depositions

Mechanical Engineerin

Natural History and Development of \u3cem\u3e Melittobia acasta \u3c/em\u3e on \u3cem\u3e Megachile rotunda \u3c/em\u3e

Alfalfa is one of the most economically important crops in North America. To produce alfalfa seed, a pollinator must release plant reproductive organs by applying pressure to keel petals. The alfalfa leafcutting bee, Megachile rotundata, is the primary commercial pollinator of alfalfa. U.S. bee managers struggle to maintain populations due to many mortality factors. One cause is attack from parasitoid wasps such as Melittobia acasta. Females can lay hundreds of eggs and have multiple generations, which can decimate bee stocks. Chapter Two investigates the life cycle and base temperature that allows development of M. acasta on bee hosts. In each of 20 vials, I exposed four bee larvae (prepupae) to several wasps and kept them at 30°C. Wasp progenies were observed daily until death. I described 12 distinct life stages, and adult wasps emerged in 16 to 20 days. I also raised M. acasta from eggs to adults along a temperature gradient bar. Statistical analysis revealed the minimum temperature for development was 8.5°C and that development from egg to adult averaged 305.8-degree days. Chapter Three determined the M. rotundata life stages upon which wasps lay eggs and offspring survive. I also determined M. acasta female survival on resources found in bee nests (an empty cell, a provision mass with and without a bee egg, and a bee prepupa). Each nest resource was exposed to a wasp (replicated 40 times). Wasps survived an average of 5, 8, and 34 days on an empty cell, either mass provision, and the bee prepupa, respectively. I also exposed 40 replicates of bee larvae and each of the pupal stages to 10-20 wasps. Wasps laid eggs on bee prepupae and their offspring developed to adulthood, while offspring from eggs laid on pupae usually died. This showed that if a wasp emerged in the field, it could live long enough for newly developed bee prepupae to serve as hosts. This research helps in understanding leafcutting bees as hosts, alert M. acasta biology when using alfalfa s bee managers to the need for controlling these wasps during bee incubation and supports future development and application of management strategies

Health and Outdoor Settings: A Summary of the Coalition for Education in the Outdoors Pre-Symposium Workshop, 2018

At the Coalition for Education in the Outdoors (CEO) 14th Biennial Research Symposium, researchers and practitioners explored the intersection between outdoor education settings and practices and human health during a pre-symposium workshop. Guided by a supposition that outdoor education experiences impact one or more dimensions of health, participants first aligned around a collective foundation of 1) definitions of nature and health and 2) formative scholarship in outdoor exposure and natural elements. With this foundation, existing paradigms were questioned: Are mainstay methodologies used in outdoor education efficacious, particularly if researchers are to engage with cross-disciplinary research teams or seek new funding sources? Given the United States’ increasing urbanization, should those working in outdoor recreation reconsider the prevailing idealization of pristine landscapes (e.g., mountain vistas and whitewater rapids), and instead celebrate both “sequoias and street trees”? Moreover, questions regarding the long-term health benefits of outdoor education remain largely unanswered. These questions resulted in the identification of gaps in research and practice. “Dosage” of outdoor exposure was one common query, as were concerns of social justice. Ultimately, workshop attendees expressed support for continued work in the intersection of health and outdoor education. This research note summarizes the Health & Outdoor Settings workshop and resulting recommended steps for subsequent research efforts

The Enigmatic Function of Chandelier Cells

Chandelier (or axo-axonic) cells are one of the most distinctive GABAergic interneurons in the brain. Their exquisite target specificity for the axon initial segment of pyramidal neurons, together with their GABAergic nature, long suggested the possibility that they provide the ultimate inhibitory control of pyramidal neuron output. Recent findings indicate that their function may be more complicated, and perhaps more interesting, than initially believed. Here we review these recent developments and their implications. We focus in particular on whether chandelier cells may provide a depolarizing, excitatory effect on pyramidal neuron output, in addition to a powerful inhibition

IR Kuiper Belt Constraints

We compute the temperature and IR signal of particles of radius $a$ and albedo $\alpha$ at heliocentric distance $R$, taking into account the emissivity effect, and give an interpolating formula for the result. We compare with analyses of COBE DIRBE data by others (including recent detection of the cosmic IR background) for various values of heliocentric distance, $R$, particle radius, $a$, and particle albedo, $\alpha$. We then apply these results to a recently-developed picture of the Kuiper belt as a two-sector disk with a nearby, low-density sector (40<R<50-90 AU) and a more distant sector with a higher density. We consider the case in which passage through a molecular cloud essentially cleans the Solar System of dust. We apply a simple model of dust production by comet collisions and removal by the Poynting-Robertson effect to find limits on total and dust masses in the near and far sectors as a function of time since such a passage. Finally we compare Kuiper belt IR spectra for various parameter values.Comment: 34 pages, LaTeX, uses aasms4.sty, 11 PostScript figures not embedded. A number of substantive comments by a particularly thoughtful referee have been addresse

Modelling extreme concentration from a source in a turbulent flow over rough wall

The concentration fluctuations in passive plumes from an elevated and a groundlevel source in a turbulent boundary layer over a rough wall were studied using large eddy simulation and wind tunnel experiment. The predictions of statistics up to second order moments were thereby validated. In addition, the trend of relative fluctuations far downstream for a ground level source was estimated using dimensional analysis. The techniques of extreme value theory were then applied to predict extreme concentrations by modelling the upper tail of the probability density function of the concentration time series by the Generalised Pareto Distribution. Data obtained from both the simulations and experiments were analysed in this manner. The predicted maximum concentration (?0) normalized by the local mean concentration (Cm) or by the local r.m.s of concentration fluctuation (crms), was extensively investigated. Values for ?0/Cm and ?0/crms as large as 50 and 20 respectively were found for the elevated source and 10 and 15 respectively for the ground-level source

Emittance compensation with dynamically optimized photoelectron beam profiles

Much of the theory and experimentation concerning creation of a high-brightness electron beam from a photocathode, and then applying emittance compensation techniques, assumes that one must strive for a uniform density electron beam, having a cylindrical shape. On the other hand, this shape has large nonlinearities in the space-charge field profiles near the beam's longitudinal extrema. These nonlinearities are known to produce both transverse and longitudinal emittance growth. On the other hand, it has recently been shown by Luiten that by illuminating the cathode with an ultra-short laser pulse of appropriate transverse profile, a uniform density, ellipsoidally shaped bunch is dynamically formed, which then has linear space-charge fields in all dimensions inside of the bunch. We study here this process, and its marriage to the standard emittance compensation scenario that is implemented in most recent photoinjectors. It is seen that the two processes are compatible, with simulations indicating a very high brightness beam can be obtained. The robustness of this scheme to systematic errors is examined. Prospects for experimental tests of this scheme are discussed

Liquid Chromatography Mass Spectrometry-Based Proteomics: Biological and Technological Aspects

Mass spectrometry-based proteomics has become the tool of choice for identifying and quantifying the proteome of an organism. Though recent years have seen a tremendous improvement in instrument performance and the computational tools used, significant challenges remain, and there are many opportunities for statisticians to make important contributions. In the most widely used "bottom-up" approach to proteomics, complex mixtures of proteins are first subjected to enzymatic cleavage, the resulting peptide products are separated based on chemical or physical properties and analyzed using a mass spectrometer. The two fundamental challenges in the analysis of bottom-up MS-based proteomics are as follows: (1) Identifying the proteins that are present in a sample, and (2) Quantifying the abundance levels of the identified proteins. Both of these challenges require knowledge of the biological and technological context that gives rise to observed data, as well as the application of sound statistical principles for estimation and inference. We present an overview of bottom-up proteomics and outline the key statistical issues that arise in protein identification and quantification.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS341 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

The historical dependency of organic carbon burial efficiency

Many studies have viewed lakes as quasi-static systems with regard to the rate of organic carbon (OC) burial, assuming that the dominant control on BE is sediment mineralization. However, in systems undergoing eutrophication or oligotrophication (i.e., altered nutrient loading), or climatic forcing, the changes in primary production will vary on both longer (> 10 yr) and shorter (seasonal) timescales, influencing the rate of OC accumulation and subsequent permanent burial. Here, we consider the extent to which permanent OC burial reflects changing production in a deep monomictic lake (Rostherne Mere, UK) that has been culturally eutrophied (present TP>200 μg L-1), but has undergone recent reductions in nutrient loading. We compare multi-year dynamics of OC fluxes using sediment traps to longer-term burial rates estimated from two 210Pb-dated sediment cores. The recent sediment record demonstrates that most of the autochthonous OC is preserved (∼95% of OC captured in the deep trap and 86% of the NEP in the contemporary system), contrary to widely held assumptions that this more labile, algal-dominated OC component is not well preserved in lake sediments. A revised method for calculating BE for lakes which have undergone changes in primary productivity in recent decades is developed, which reduces some of problems inherent in existing approaches using historical sediment records averaged over the last 25-150 yr. We suggest that an appreciation of lakes in all biomes as ecosystems responding dynamically to recent human impact and climate change (for example) can improve up-scaled regional and global estimates of lake OC burial

Functional imaging of hippocampal dysfunction among persons with Alzheimer’s disease: a proof-of-concept study

Cholinergic deficits are an early and functionally significant manifestation of Alzheimer’s disease (AD). These deficits contribute to impairment of hippocampally mediated information processing, including declarative memory impairments and abnormal auditory sensory gating. A functional imaging technique that facilitates identification of changes in cholinergically dependent hippocampal information processing would be of considerable use in the study and clinical evaluation of persons with this condition. Techniques that interrogate hippocampal function passively, ie, in a manner requiring no cognitive effort or novel task learning during the neuroimaging procedure, would also be especially useful in this cognitively impaired population. The functional magnetic resonance imaging sensory gating paradigm developed at the University of Colorado, CO, USA, is a functional neuroimaging technique that possesses both of these characteristics. We developed a demonstration project using this paradigm in which we passively interrogated hippocampal function in two subjects with probable AD of mild severity. Imaging data were quick and easy in these subjects and served usefully as an initial demonstration of the feasibility of using this neuroimaging method in this population. Preliminary analyses of the data obtained from these subjects identified abnormal blood oxygen level-dependent responses when compared with four healthy comparators, and the pattern of these responses was consistent with impaired function of the auditory sensory gating network. The strengths and limitations of this neuroimaging paradigm and the additional issues that require investigation in order to continue its development into a research and clinical technique for use in this population are discussed