Energy-balance climate models

An introductory survey of the global energy balance climate models is presented with an emphasis on analytical results. A sequence of increasingly complicated models involving ice cap and radiative feedback processes are solved and the solutions and parameter sensitivities are studied. The model parameterizations are examined critically in light of many current uncertainties. A simple seasonal model is used to study the effects of changes in orbital elements on the temperature field. A linear stability theorem and a complete nonlinear stability analysis for the models are developed. Analytical solutions are also obtained for the linearized models driven by stochastic forcing elements. In this context the relation between natural fluctuation statistics and climate sensitivity is stressed

A method to quantitatively evaluate Hamaker constant using the jump-into-contact effect in Atomic Force microscopy

We find that the jump-into-contact of the cantilever in the atomic force microscope (AFM) is caused by an inherent instability in the motion of the AFM cantilever. The analysis is based on a simple model of the cantilever moving in a nonlinear force field. We show that the jump-into-contact distance can be used to find the interaction of the cantilever tip with the surface. In the specific context of the attractive van der Waals interaction, this method can be realized as a new method of measuring the Hamaker constant for materials. The Hamaker constant is determined from the deflection of the cantilever at the jump-into-contact using the force constant of the cantilever and the tip radius of curvature, all of which can be obtained by measurements. The results have been verified experimentally on a sample of cleaved mica, a sample of Si wafer with natural oxide and a silver film, using a number of cantilevers with different spring constants. We emphasize that the method described here is applicable only to surfaces that have van der Waals interaction as the tip-sample interaction. We also find that the tip to sample separation at the jump-into-contact is simply related to the cantilever deflection at this point, and this provides a method to exactly locate the surface.Comment: 11 pages, 4 figures, 1 tabl

The Wisconsin H-Alpha Mapper Northern Sky Survey

The Wisconsin H-Alpha Mapper (WHAM) has surveyed the distribution and kinematics of ionized gas in the Galaxy above declination -30 degrees. The WHAM Northern Sky Survey (WHAM-NSS) has an angular resolution of one degree and provides the first absolutely-calibrated, kinematically-resolved map of the H-Alpha emission from the Warm Ionized Medium (WIM) within ~ +/-100 km/s of the Local Standard of Rest. Leveraging WHAM's 12 km/s spectral resolution, we have modeled and removed atmospheric emission and zodiacal absorption features from each of the 37,565 spectra. The resulting H-Alpha profiles reveal ionized gas detected in nearly every direction on the sky with a sensitivity of 0.15 R (3 sigma). Complex distributions of ionized gas are revealed in the nearby spiral arms up to 1-2 kpc away from the Galactic plane. Toward the inner Galaxy, the WHAM-NSS provides information about the WIM out to the tangent point down to a few degrees from the plane. Ionized gas is also detected toward many intermediate velocity clouds at high latitudes. Several new H II regions are revealed around early B-stars and evolved stellar cores (sdB/O). This work presents the details of the instrument, the survey, and the data reduction techniques. The WHAM-NSS is also presented and analyzed for its gross properties. Finally, some general conclusions are presented about the nature of the WIM as revealed by the WHAM-NSS.Comment: 42 pages, 14 figures (Fig 6-9 & 14 are full color); accepted for publication in 2003, ApJ, 149; Original quality figures (as well as data for the survey) are available at http://www.astro.wisc.edu/wham

Continuous near-bottom gravity measurements made with a BGM-3 gravimeter in DSV Alvin on the East Pacific Rise crest near 9°31 'N and 9°50'N

A Bell BGM-3 gravimeter has been used to collect continuous, underway, near-bottom (3- to 10-m altitude) gravity measurements from the deep-diving submersible DSV Alvin during surveys on the East Pacific Rise (EPR) crest near 9° 31'N and 9° 50'N. Closely spaced (20- to 30-m) gravity measurements were made along transects up to 8 km-long in both regions. Repeatability of measurements made at the same location on different dives is ~ 0.3 mGal. Along-track spatial resolution of anomalies is ~130-160 m, with the limiting factors being precision and sampling rate of the pressure gauge depth data used to calculate vertical accelerations of the submersible. The average upper crustal density of the ridge crest determined from the relationship between depth and free-water gravity anomalies varies greatly between 9 °31 'N and 9° 50'N. Average upper crustal densities of2410 kg/m3 for the 9° 50'N area and 2690 kg/m3 for the 9° 31'N area were calculated. The different densities are not due to differing geometry of the Layer 2A-2B boundary or a regional cross-axis gravity gradient. Differences in porosity of the shallow crustal rocks, or a difference in the proportion of low-density extrusives to higher-density dikes and sills within Layer 2A in these two areas, are the likely causes of the different upper crustal densities. Bouguer gravity anomalies near the EPR axis are primarily small amplitude (0.5-2 mGal), are a few hundred meters across, and appear to be lineated parallel to the axis. Larger-amplitude Bouguer anomalies of up to 4 mGal were found at a few locations across the crestal plateau and are associated with pillow ridges composed of lavas which are clearly younger than the surrounding seafloor. These ridges have distinct chemical compositions compared to lavas from the axial summit collapse trough (ASCT) at the same latitude. Probable sources of the 0.5- to 2-mGal anomalies observed on the summit plateau include areas of collapsed and fissured terrain and dike swarms feeding melt through Layer 2A to the surface. A grid survey of the ridge axis near 9° 50'N shows Bouguer anomalies lineated along the axis, suggesting that dike swarms do contribute to the observed Bouguer anomalies. The along-axis continuity of the gravity anomalies is disrupted at a 75-m offset of the ASCT, suggesting that shallow feeders of lava to the surface may be segmented on a finer scale than the deeper crustal magmatic system. This initial study confirms the ability to conduct high-resolution, near-bottom, continuous gravity measurements from Alvin. It also provides important information on how the shallow crustal structure of a fast spreading mid-ocean ridge develops and how it varies with the surface morphology

Fetal tracheolaryngeal airway obstruction: prenatal evaluation by sonography and MRI

We reviewed the sonographic and MRI findings of tracheolaryngeal obstruction in the fetus. Conditions that can cause tracheolaryngeal obstruction include extrinsic causes such as lymphatic malformation, cervical teratoma and vascular rings and intrinsic causes such as congenital high airway obstruction syndrome (CHAOS). Accurate distinction of these conditions by sonography or MRI can help facilitate parental counseling and management, including the decision to utilize the ex utero intrapartum treatment (EXIT) procedure

The City: Art and the Urban Environment

The City: Art and the Urban Environment is the fifth annual exhibition curated by students enrolled in the Art History Methods class. This exhibition draws on the students’ newly developed expertise in art-historical methodologies and provides an opportunity for sustained research and an engaged curatorial experience. Working with a selection of paintings, prints, and photographs, students Angelique Acevedo ’19, Sidney Caccioppoli ’21, Abigail Coakley ’20, Chris Condon ’18, Alyssa DiMaria ’19, Carolyn Hauk ’21, Lucas Kiesel ’20, Noa Leibson ’20, Erin O’Brien ’19, Elise Quick ’21, Sara Rinehart ’19, and Emily Roush ’21 carefully consider depictions of the urban environment in relation to significant social, economic, artistic, and aesthetic developments. [excerpt]https://cupola.gettysburg.edu/artcatalogs/1029/thumbnail.jp

The identification of reasons, solutions, and techniques informing a theory-based intervention targeting recreational sports participation

This study is the 3rd piece of formative research utilizing the theory of planned behavior to inform the development of a behavior change intervention. Focus groups were used to identify reasons for and solutions to previously identified key beliefs in addition to potentially effective behavior change techniques. A purposive sample of 22 first-year undergraduate students (n = 8 men; M  = 19.8 years, SD = 1.3 years) attending a university in the North of England was used. Focus groups were audio-recorded; recordings were transcribed verbatim, analyzed thematically, and coded for recurrent themes. The data revealed 14 reasons regarding enjoyment, 11 reasons for friends' approval, 11 reasons for friends' own participation, 14 reasons for the approval of family members, and 10 solutions to time constraints. Twelve distinct techniques were suggested to attend to these reasons and solutions. This qualitative research will be used to inform the development of a theory-based intervention to increase students' participation in university recreational sports