Annealing of fast neutron damage in impurity-conducting n-type germanium

Thermal annealing of fast neutron induced changes in electrical properties of highly doped n-type germaniu

FREE-FLIGHT MEASUREMENTS OF STATIC AND DYNAMIC STABILITY OF MODELS OF THE PROJECT MERCURY RE-ENTRY CAPSULE AT MACH NUMBERS 3 AND 9.5

Static & dynamic stability of mercury reentry capsule scale models at mach 3 & 9.

Non-radial oscillations in M-giant semi-regular variables: Stellar models and Kepler observations

The success of asteroseismology relies heavily on our ability to identify the frequency patterns of stellar oscillation modes. For stars like the Sun this is relatively easy because the mode frequencies follow a regular pattern described by a well-founded asymptotic relation. When a solar like star evolves off the main sequence and onto the red giant branch its structure changes dramatically resulting in changes in the frequency pattern of the modes. We follow the evolution of the adiabatic frequency pattern from the main sequence to near the tip of the red giant branch for a series of models. We find a significant departure from the asymptotic relation for the non-radial modes near the red giant branch tip, resulting in a triplet frequency pattern. To support our investigation we analyze almost four years of Kepler data of the most luminous stars in the field (late K and early M type) and find that their frequency spectra indeed show a triplet pattern dominated by dipole modes even for the most luminous stars in our sample. Our identification explains previous results from ground-based observations reporting fine structure in the Petersen diagram and sub ridges in the period-luminosity diagram. Finally, we find `new ridges' of non-radial modes with frequencies below the fundamental mode in our model calculations, and we speculate they are related to f modes.Comment: 8 page, 5 figures, accepted by ApJL (ApJ, 788, L10

Multi-Gain-Stage InGaAs Avalanche Photodiode with Enhanced Gain and Reduced Excess Noise

We report the design, fabrication, and test of an InGaAs avalanche photodiode (APD) for 950-1650 nm wavelength sensing applications. The APD is grown by molecular beam epitaxy on InP substrates from lattice-matched InGaAs and InAlAs alloys. Avalanche multiplication inside the APD occurs in a series of asymmetric gain stages whose layer ordering acts to enhance the rate of electron-initiated impact ionization and to suppress the rate of hole-initiated ionization when operated at low gain. The multiplication stages are cascaded in series, interposed with carrier relaxation layers in which the electric field is low, preventing avalanche feedback between stages. These measures result in much lower excess multiplication noise and stable linear-mode operation at much higher avalanche gain than is characteristic of APDs fabricated from the same semiconductor alloys in bulk. The noise suppression mechanism is analyzed by simulations of impact ionization spatial distribution and gain statistics, and measurements on APDs implementing the design are presented. The devices employing this design are demonstrated to operate at linear-mode gain in excess of 6000 without avalanche breakdown. Excess noise characterized by an effective impact ionization rate ratio below 0.04 were measured at gains over 1000

Trauma and Trichotillomania: A Tenuous Relationship

Some have argued that hair pulling in trichotillomania (TTM) is triggered by traumatic events, but reliable evidence linking trauma to TTM is limited. However, research has shown that hair pulling is associated with emotion regulation, suggesting a connection between negative affect and TTM. We investigated the associations between trauma, negative affect, and hair pulling in a cross-sectional sample of treatment seeking adults with TTM (N=85). In the current study, participants’ self-reported traumatic experiences were assessed during a structured clinical interview, and participants completed several measures of hair pulling severity, global TTM severity, depression, anxiety, experiential avoidance, and quality of life. Those who experienced trauma had more depressive symptoms, increased experiential avoidance, and greater global TTM severity. Although the presence of a trauma history was not related to the severity of hair pulling symptoms in the past week, depressive symptoms mediated the relationship between traumatic experiences and global TTM severity. These findings cast doubt on the notion that TTM is directly linked to trauma, but suggest that trauma leads to negative affect that individuals cope with through hair pulling. Implications for the conceptualization and treatment of TTM are discussed

Non-pollinator fig wasp impact on the reproductive success of an invasive fig tree: why so little?

Classical biological control agents fail to achieve an impact on their hosts for a variety of reasons and an understanding of why they fail can help shape decisions on subsequent releases. Ornamental Ficus microcarpa is a widely planted avenue fig tree that is invasive in countries where its pollinator (Eupristina verticillata) is also introduced. This tree also supports more than 20 species of non-pollinating fig wasps (NPFW) that feed in the figs and have the potential to reduce the plant’s reproduction. Odontofroggatia galili, one of the most widely introduced NPFW, has larvae that develop in galled ovules that might otherwise develop into seeds or support pollinator larvae. We examined the distribution and relative abundance of the pollinator and O. galili on F. microcarpa in China, towards the northern limit of the tree’s natural range, and in Italy where the two species have been introduced. Where they co-existed, we also recorded the impact of varying densities of O. galili on F. microcarpa seed and pollinator production. O. galili and E. verticillata displayed contrasting habitat preferences in China, with O. galili almost absent from warmer sites. O. galili abundance and sex ratios varied between the natural and introduced ranges. Figs with more O. galili contained fewer seeds and pollinator offspring, but reproduction was rarely inhibited totally. Additional species with a greater impact in the figs they occupy are needed if biocontrol of F. microcarpa is to be effective

Vacancies, twins, and the thermal stability of ultrafine-grained copper

Ultrafine-grained metals have impressive strength but lack the thermal stability necessary for most applications. Nano-scale, deformation twinned copper microstructures exhibit a rare combination of strength and stability. While storing less energy in their interfaces than other nanostructured metals, they also exhibit lower vacancy supersaturations, reducing the driving force and mobility for microstructure evolution. From a thermal stability perspective, the nano-twinned microstructure may thus be preferred over the more commonly produced nano-scale equiaxed microstructures