Physics and Astronomy

AFM was used to non-invasively characterize the nanoscale crystal interfaces of the organic solar cells. Needlelike growths dominate the large, ordered regions. The crystal structures display circular and bow-tie growth patterns and, upon annealing, the crystals become more well-defined, larger in size, and the needle-like features are longer. Spherical growths are observed on the film surface, consistent with the spherical PCBM crystals seen in other BHJs. 4,5 Upon annealing, both crystal structures become much more well-defined, with boundaries between crystal grains becoming clearly visible and demarcated by film separation as is expected for film crystallization.

Since durable technology emerged between 3.4 and 3.2 million years ago, stone tools served as a major material means that hominins used to survive. Determining how different lithic tools functioned is a principal question in human evolution. The main experimentally based approach to the functional study of lithic technology uses stereo and incident-light microscopy, and is known as the Keeley Method. Although this method has demonstrated success in linking the morphology of microwear traces on flint tools to the function of the tool, there is no agreed upon model of how these microwear polishes form. At the same time, the characterization of these polishes has been a largely qualitative process. Herein, we use the atomic force microscope (AFM) to scan microwear traces on Middle Palaeolithic (Mousterian) tools from Weasel Cave, Russia to show quantitative data and small scale features of microwear polishes interpreted (using the Keeley Method) as due to contact with meat, fresh hide, dry hide, bone, wood, and hafting. These results follow those of to the previous AFM study on the experimental tools, namely that the meat and dry hide polishes are the least developed polishes with smaller changes in roughness and that the bone polish and wood polishes are more highly developed polishes and exhibit larger changes in roughness. SCANNING 33: 1-12, 2011. r 2011 Wiley Periodicals, Inc.

The morphology of organic solar cell bulk heterojunctions were characterized using atomic force microscopy (AFM). The RMS roughness of solar cells composed of 1, 3-bis [4-(N, N-diisopentylamino)-2, 6-dihydroxyphenyl] squaraine [DiPSQ (OH) $ _2 $] and phenyl [C $ _ {61} $]-butyric acid methyl ester [PCBM] through spin casting were measured. Solar cells of various blend concentrations, anneal times, and cooling methods were characterized. Through RMS roughness analysis we can study the crystallization process in solar cell ...

Forest University -Crystalline organic semiconductors often display carrier mobilities that vary with environmental conditions and fabrication parameters. Additionally, the electrical properties of organic thin-film devices are highly dependent on film structure, crystallinity, and molecular packing. In solution-deposited polycrystalline thin-films, the regions between crystals often affect the overall device performance, as molecular ordering and crystal structure may differ significantly from neighboring regions. Device characterization and Kelvin Probe Force Microscopy (KPFM) is used to analyze the electrical properties of grain boundaries, electrodes, and crystalline regions within 2,8-difluoro-5,11-triethysilylethynyl anthradithiophene (diF TESADT) thin-film transistor surfaces. The influence of both atmospheric dopants and exposure time is examined and explained in the context of device characterization and interfacial effects.

Dust accumulation on thermal radiator surfaces planned for lunar exploration will significantly reduce their efficiency. Evidence from the Apollo missions shows that an insulating layer of dust accumulated on radiator surfaces could not be removed and caused serious thermal control problems. Temperatures measured at different locations the magnetometer on Apollo 12 were 38°C warmer than expected due to lunar dust accumulation. In this paper, we report on the application of the Electrodynamic Dust Shield (EDS) technology being developed in our NASA laboratory and applied to thermal radiator The EDS uses electrostatic and dielectrophoretic forces generated by a grid of electrodes running a 2 IJ,A electric current to remove dust particles from surfaces. Working prototypes of EDS systems on solar panels and on radiators developed at vacuum efficiencies above EDS prototypes on u~'uv'''' and rigid were developed

The solubility of vapors within semicrystalline polyethylenes produced in the gas phase process is examined. Experimentally measured solubilities of ethylene, 1-butene, isobutane, isopentane, 1-hexene, and n-hexane as a function of temperature, pressure, and vapor composition are reported for a series of semicrystalline linear low density polyethylenes, and a model for predicting these results is presented in detail. This paper demonstrates that conventional thermodynamic methods, which accurately predict polymer phase behavior in fluid systems, fail to account for a critical concept associated with semicrystalline polymers; the elastic constraint. Through application of a simple thermodynamic model addressing this effect, vapor solubility in such systems can be accurately predicted using a limited number of adjustable parameters.

This paper extends the previous article by the authors on the solubility of hydrocarbon vapors in semicrystalline polyethylenes produced in the gas phase process. That work demonstrates a computational model for solubility based on an activity coefficient modification of the Sako–Wu–Prausnitz equation of state. In that work, by fitting a key parameter, one related to the constraint of tie chains on polymer fluid behavior, to a single isopentane solubility isotherm, accurate predictions of hydrocarbon solubility in polymer granules over a range of temperature, pressure, and composition are reported. In the present work, additional experimental solubility data are reported, an error in the authors' previous article is corrected, and a useful parameterization method that improves the predictive capabilities of the model is demonstrated. By using the model to predict much of the authors' own experimental data, as well as that published by others in the field, it is demonstrated ...

The solubility of vapors within semicrystalline polyethylenes produced in the gas phase process is examined. Experimentally measured solubilities of ethylene, 1-butene, isobutane, isopentane, 1-hexene, and n-hexane as a function of temperature, pressure, and vapor composition are reported for a series of semicrystalline linear low density polyethylenes, and a model for predicting these results is presented in detail. This paper demonstrates that conventional thermodynamic methods, which accurately predict polymer phase behavior in fluid systems, fail to account for a critical concept associated with semicrystalline polymers; the elastic constraint. Through application of a simple thermodynamic model addressing this effect, vapor solubility in such systems can be accurately predicted using a limited number of adjustable parameters.

Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmospheres and underlying pulsation mechanisms. For example, measuring variations in TiO, VO, and ZrO with phase can be used to help determine whether these molecular species are produced in an extended region above the layers where Balmer line emission occurs or below this shocked region. Using the same methods, the Balmer line increment, where the strongest Balmer line at phase zero is Hd and not Ha, can be measured and explanations tested, along with another peculiarity, the absence of the Hv line in the spectra of Mira variables when the other Balmer lines are strong. We present new spectra covering the spectral range from 6200 to 9000 of 20 Mira variables. A relationship between variations in the Ca II A IR triplet and Ha as a function of phase support the hypothesis that HvÏs observational characteristics result from an interaction of Hv photons with the Ca II H line. New periods and epochs of variability are also presented for each star.

ABSTRACT Spectra from the International Ultraviolet Explorer taken in 1989 September over one full orbital period of U Cephei (U Cep, HD 5796) are analyzed. The TLUSTY and SYNSPEC stellar atmospheric simulation programs are used to generate synthetic spectra to which U Cep continuum levels are normalized. Absorption lines attributed to the photosphere are divided out to isolate mass flow and accretion spectra. A radial velocity curve is constructed for conspicuous gas stream features, and shows evidence for a transient flow during secondary eclipse with outward velocities ranging between 200 and 350 km s–1, and a number density of (3 ± 2) × 1010 cm–3. The validity of C IV 1548 and 1550 and Si IV 1393 and 1402 lines are re-examined in the context of extreme rotational blending effects. A G-star to B-star mass transfer rate of (5 ± 4) × 10–9M ☉ yr–1 is calculated as an approximate upper limit, and a model system is presented.

CM Draconis is one of the few known M-dwarf eclipsing binary systems. It has been the target for a search for planetary transits by our group and others. During the monitoring of this system it went through a period of high stellar activity, with flares occurring clustered in one orbital phase range, from 0.25 to 0.55. Most of them occurred in the lower part of that range and all over a span of less than a week. We present the results of the last two years of monitoring CM Dra.

Six flare events detected in CM Draconis are presented. These flares were detected over three nights of observations in May 2006 as part of a transiting planet search program at Appalachian State. The observation time of the system totals 105 hours to date, yielding an estimated flare rate of 0.057 flares/hour.

We follow up on single coverage UBVRcIc light curves taken in 2011 and analyses. Our present BVRcIc light curves with ample coverage were taken October and November 2013 and January 2014 with the Dark Sky Observatory 0.81-meter reflector of Appalachian State University. They reveal the early-type V530 And as a totally eclipsing shallow or critical contact solar-type binary rather than semidetached near-contact one. In our extended period study, over a 14.25-year interval, we find a continuously decreasing period. This fits the scenario of magnetic braking for solar-type binaries. The temperatures of the primary and secondary components are estimated at 6750 and 6030 K. The component temperature difference is large for a contact binary. The fill-out, however, is a mere 5% so it is near critical contact. The mass ratio, M2 / M1, was found to be 0.386. Two star spots, probably magnetic in origin, were determined. We suspect that the binary has recently achieved physical contact for the...