The October 27-28, 1986, FIRE cirrus case study: Cloud microstructure

Using aircraft in-situ measurements, the microphysics of cirrus clouds observed on 28 Oct. 1986 during FIRE were examined. Results are presented as one component of a coordinated study of the cirrus on the day. The study contributes to the understanding of cold clouds by: (1) providing microphysical data to supplement satellite and aircraft data for investigating cirrus cloud radiative effects; (2) providing more complete information on ice particle evolution and cloud forcing mechanisms than has been available through the use of instrumentation with higher resolution and more accurate calibration; (3) expanding the knowledge of the particle characteristics in cold liquid water clouds, through improved instrumentation and by making use of sensors on other platforms, such as lidar; and (4) by estimating the ice nucleus concentrations active at low temperatures in the upper troposphere from the concentrations of ice particles in colloidally stable liquid water clouds

Ramsey Theory Problems over the Integers: Avoiding Generalized Progressions

Two well studied Ramsey-theoretic problems consider subsets of the natural numbers which either contain no three elements in arithmetic progression, or in geometric progression. We study generalizations of this problem, by varying the kinds of progressions to be avoided and the metrics used to evaluate the density of the resulting subsets. One can view a 3-term arithmetic progression as a sequence $x, f_n(x), f_n(f_n(x))$, where $f_n(x) = x + n$, $n$ a nonzero integer. Thus avoiding three-term arithmetic progressions is equivalent to containing no three elements of the form $x, f_n(x), f_n(f_n(x))$ with $f_n \in\mathcal{F}_{\rm t}$, the set of integer translations. One can similarly construct related progressions using different families of functions. We investigate several such families, including geometric progressions ($f_n(x) = nx$ with $n > 1$ a natural number) and exponential progressions ($f_n(x) = x^n$). Progression-free sets are often constructed "greedily," including every number so long as it is not in progression with any of the previous elements. Rankin characterized the greedy geometric-progression-free set in terms of the greedy arithmetic set. We characterize the greedy exponential set and prove that it has asymptotic density 1, and then discuss how the optimality of the greedy set depends on the family of functions used to define progressions. Traditionally, the size of a progression-free set is measured using the (upper) asymptotic density, however we consider several different notions of density, including the uniform and exponential densities.Comment: Version 1.0, 13 page

Hormone Replacement Therapy and Risk for Neurodegenerative Diseases

Over the past two decades, there has been a significant amount of research investigating the risks and benefits of hormone replacement therapy (HRT) with regards to neurodegenerative disease. Here, we review basic science studies, randomized clinical trials, and epidemiological studies, and discuss the putative neuroprotective effects of HRT in the context of Alzheimer's disease, Parkinson's disease, frontotemporal dementia, and HIV-associated neurocognitive disorder. Findings to date suggest a reduced risk of Alzheimer's disease and improved cognitive functioning of postmenopausal women who use 17β-estradiol. With regards to Parkinson's disease, there is consistent evidence from basic science studies for a neuroprotective effect of 17β-estradiol; however, results of clinical and epidemiological studies are inconclusive at this time, and there is a paucity of research examining the association between HRT and Parkinson's-related neurocognitive impairment. Even less understood are the effects of HRT on risk for frontotemporal dementia and HIV-associated neurocognitive disorder. Limits to the existing research are discussed, along with proposed future directions for the investigation of HRT and neurodegenerative diseases

Generation of the Transient Electrical and Spontaneous Magnetic Fields by Solid State Combustion

Experiments revealed that transient electric field intensities up to 2.5 V/cm were generated during the initial period of combustion synthesis of the ferromagnetic products before the maximum temperature was reached. This occurred when the iron particles were partially oxidized and the reaction product was mainly magnetite sFe3O4d. The electromagnetic field caused spontaneous magnetization of the product in the postcombustion zone. Magnetic field values up to 4 µT formed after the sample temperature fell below the Curie temperature and the initial reactants were completely converted to the ferromagnetic phase PbFe12O19. Increasing the volume of the samples increases the absolute residual magnetic field magnitude after cooling. We present possible mechanisms of the electromagnetic field generation during the combustion

Erosion Mitigation at Fort Hase Beach and at Pyramid Rock Recreational Areas

The U.S. Marine Corps Base Hawaii is responsible for management of the military lands at Mokapu Peninsula in the Kaneohe Bay area, on the island of Oahu, including the shoreline recreational areas known as Fort Hase and Pyramid Rock Beaches. These two beach parks are popular recreational sites and are used extensively by military personnel. The beach at Pyramid Rock Recreational Subarea is also open to the general public on weekends. Unfortunately, this use has resulted in considerable stress to the physical characteristics of the parks. The lack of directional walkways has led to multiple paths across and through the dune vegetation. Inadequate drainage from a shower facility and rainfall runoff have led to erosion in the parking lot at Pyramid Rock Recreational Subarea. High waves have exacerbated the erosion caused by unregulated foot traffic at the Fort Hase beach park, in particular, and have led to the formation of a .5 meter coastal escarpment at the Fort Hase beach and the exposure of an archaeological site. To assure effective and informed management of their coastal and cultural resources, the Marine Corps Base Hawaii (MCBH) is interested in developing methods to mitigate coastal erosion problems and to simultaneously improve the recreational use of these beach parks in accordance with their administrative directives and need to comply with federal statutes. Hence, the purpose of this study has been to examine the environmental characteristics of the two recreational parks; Fort Hase and Pyramid Rock beaches, and to make recommendations on non-structural ways to mitigate both anthropogenic and natural impacts to these parks while assuring that historical and cultural resources are protected.Ogden Environmental and Energy Services Co., Inc

NMR Chemical Shifts of Trace Impurities: Common Laboratory Solvents, Organics, and Gases in Deuterated Solvents Relevant to the Organometallic Chemist

Tables of ^1H and ^(13)C NMR chemical shifts have been compiled for common organic compounds often used as reagents or found as products or contaminants in deuterated organic solvents. Building upon the work of Gottlieb, Kotlyar, and Nudelman in the Journal of Organic Chemistry, signals for common impurities are now reported in additional NMR solvents (tetrahydrofuran-d_8, toluene-d_8, dichloromethane-d_2, chlorobenzene-d_5, and 2,2,2-trifluoroethanol-d_3) which are frequently used in organometallic laboratories. Chemical shifts for other organics which are often used as reagents or internal standards or are found as products in organometallic chemistry are also reported for all the listed solvents

Physical Activity and Hippocampal Sub-Region Structure in Older Adults with Memory Complaints.

BackgroundPhysical activity (PA) plays a major role in maintaining cognition in older adults. PA has been shown to be correlated with total hippocampal volume, a memory-critical region within the medial temporal lobe (MTL). However, research on associations between PA and MTL sub-region integrity is limited.ObjectiveTo examine the relationship between PA, MTL thickness, and its sub-regions, and cognitive function in non-demented older adults with memory complaints.MethodsTwenty-nine subjects aged ≥60 years, with memory complaints were recruited for this cross-sectional study. PA was tracked for 7 days using accelerometers, and average number of steps/day determined. Subjects were categorized into two groups: those who walked ≤4000 steps/day (lower PA) and those with >4000 steps/day (higher PA). Subjects received neuropsychological testing and 3T MRI scans. Nonparametric ANCOVAs controlling for age examined differences between the two groups.ResultsTwenty-six subjects aged 72.7(8.1) years completed the study. The higher PA group (n = 13) had thicker fusiform gyrus (median difference = 0.11 mm, effect size (ES) = 1.43, p = 0.001) and parahippocampal cortex (median difference = 0.12 mm, ES = 0.93, p = 0.04) compared to the lower PA group. The higher PA group also exhibited superior performance in attention and information-processing speed (median difference = 0.90, ES = 1.61, p = 0.003) and executive functioning (median difference = 0.97, ES = 1.24, p = 0.05). Memory recall was not significantly different between the two groups.ConclusionOlder non-demented individuals complaining of memory loss who walked >4000 steps each day had thicker MTL sub-regions and better cognitive functioning than those who walked ≤4000 steps. Future studies should include longitudinal analyses and explore mechanisms mediating hippocampal related atrophy

BaCu5Al8: A Structure Containing Interconnected [Al8Cu4]2- Icosahedra

BaCu5Al8 was synthesized from stoichiometric amounts of the elements by heating in a tube furnace or melting in an arc welder. BaCu5Al8 forms a variation of the NaZn13 structure in which large Ba2+ cations are surrounded by a three-dimensional network of interconnected Cu-centered, [Al8Cu4]2- icosahedra. The compound was characterized by both powder and single crystal X-ray diffraction. BaCu5Al8 crystallizes in the space group Fm5c (no.226); a = 12.2049(38) Å; Z = 8; R = 0.018; Goof = 1.16. EUCU5A18 was characterized by powder X-ray diffraction, and lattice parameters were refined from the measured 2-theta values; a = 11.9715(19) A. Magnetic susceptibility for both BaCusAlg and EuCu5Al8, and resistivity measurements on EuCu5Al8 are reported. Extended Hückel calculations on stoichiometries ranging from BaCu13 to BaCuAl12, demonstrate the tuning of the system’s stoichiometry to balance the Fermi energy and overlap populations