13,684 research outputs found
Accretion and photodesorption of CO ice as a function of the incident angle of deposition
Non-thermal desorption of inter- and circum-stellar ice mantles on dust
grains, in particular ultraviolet photon-induced desorption, has gained
importance in recent years. These processes may account for the observed gas
phase abundances of molecules like CO toward cold interstellar clouds. Ice
mantle growth results from gas molecules impinging on the dust from all
directions and incidence angles. Nevertheless, the effect of the incident angle
for deposition on ice photo-desorption rate has not been studied. This work
explores the impact on the accretion and photodesorption rates of the incidence
angle of CO gas molecules with the cold surface during deposition of a CO ice
layer. Infrared spectroscopy monitored CO ice upon deposition at different
angles, ultraviolet-irradiation, and subsequent warm-up. Vacuum-ultraviolet
spectroscopy and a Ni-mesh measured the emission of the ultraviolet lamp.
Molecules ejected from the ice to the gas during irradiation or warm-up were
characterized by a quadrupole mass spectrometer. The photodesorption rate of CO
ice deposited at 11 K and different incident angles was rather stable between 0
and 45. A maximum in the CO photodesorption rate appeared around
70-incidence deposition angle. The same deposition angle leads to the
maximum surface area of water ice. Although this study of the surface area
could not be performed for CO ice, the similar angle dependence in the
photodesorption and the ice surface area suggests that they are closely
related. Further evidence for a dependence of CO ice morphology on deposition
angle is provided by thermal desorption of CO ice experiments
Interaction Effects on the Magneto-optical Response of Magnetoplasmonic Dimers
The effect that dipole-dipole interactions have on the magneto-optical (MO)
properties of magnetoplasmonic dimers is theoretically studied. The specific
plasmonic versus magnetoplasmonic nature of the dimer's metallic components and
their specific location within the dimer plays a crucial role on the
determination of these properties. We find that it is possible to generate an
induced MO activity in a purely plasmonic component, even larger than that of
the MO one, therefore dominating the overall MO spectral dependence of the
system. Adequate stacking of these components may allow obtaining, for specific
spectral regions, larger MO activities in systems with reduced amount of MO
metal and therefore with lower optical losses. Theoretical results are
contrasted and confirmed with experiments for selected structures
Finding positive health in “fortalezas” and “comunidad”: A case study of Latinos/X in Sonoma Valley
Background: Psychological literature and needs-assessment reports emphasize that Latinos/X in Sonoma Valley continue to be impacted by the detrimental effects of the 2017 Northern California wildfires (Domínguez & Yeh, 2018), current immigration enforcement practices, higher rates of poverty, lower educational attainment, persistent barriers to health care access, and obstacles to proportionate leadership representation compared to White American families. To cope with these disparities and navigate life adversities, Sonoma Valley Latinos/X often rely on “fortalezas” [strengths] and community, political, spiritual, cultural, and physical assets. These assets, which often include meaningful interactions with family, friends, neighbors, folk healers, faith-based organizations, and community members, must be incorporated when health care, community, and social service initiatives are designed and implemented.
Method: Our community-engaged research team (CERT) used asset-based community development (ABCD) as a conceptual framework (Kretzmann & McKnight, 1993) and community-based participatory research (CBPR) (Wallerstein & Duran, 2003) as a methodological approach to explore the assets and “fortalezas” [strengths] that have enabled Latinos/X to overcome adverse experiences i n Sonoma Valley. Five focus groups and 29 in-depth interviews were conducted because these methods are well-suited for Latino/X relational styles of “platicando” [small talk] (Delgado-Romero, Singh, & De Los Santos, 2018) . Participants were 18 years or older, lived or worked i n Sonoma Valley, and self-identified as Latino/X. Our sample included Latino/X parents, grandparents, artists, folk healers, health and social service providers, community leaders, students, and school personnel. Specific locations where interviews took place include the Hanna Institute, Nuestra Voz, La Luz Center, Center for Well-Being, Boys and Girls Clubs of Sonoma Valley, the Family Resource Center in El Verano, the Sonoma Valley Community Health Center, participants’ houses, and the broader Sonoma Valley community. Our research prioritized depth of relational engagement rather than sample size (Bowden, Caine, Yohani, 2017). We discontinued data collection once our research objectives were achieved and data saturation was accomplished. For data analysis, we used quasi-statistics to quantify the frequency of asset endorsement; open, axial, and selective coding to identify and categorize the assets; and GIS software for the creation of our two asset maps.
Findings: Findings indicate that Latinos/X are marginally positioned within Sonoma Valley society. Latinos/X have coped with and adapted to adverse conditions and disparities using and relying on a variety of informal networks and formal sources of support. Their decision to rely on one source of support over another is often based on (a) the extent to which they can afford the services or support required; (b) their particular needs, goals, or objectives at the time the help i s needed; (c) their preference for support resources that honor “respeto” [respect], “personalismo” [a preference for close personal attention i n relationships], and stable and welcoming intimate relationships with others; (d) the accessibility associated with pursuing these support services (e.g., geographic and transportation limitations); and (e) the extent to which culturally relevant and Spanish-speaking support can be found.
Dissemination: All data i n this study i s co-owned with the Sonoma Valley community. With the help of our community partners, this report was disseminated in Sonoma Valley during community meetings and forums, offering residents the opportunity to provide feedback, debate preliminary results, and assess whether their voices were captured accurately. Once the community expressed that the findings were representative of the Latino/X experience in Sonoma Valley, we finalized recommendations to assist community members, government officials, and health care and social service providers in designing culturally informed social, health, and/or community programs
General Non-equilibrium Theory of Colloid Dynamics
A non-equilibrium extension of Onsager's canonical theory of thermal
fluctuations is employed to derive a self-consistent theory for the description
of the statistical properties of the instantaneous local concentration profile
n(r,t) of a colloidal liquid in terms of the coupled time evolution equations
of its mean value n(r,t) and of the covariance {\sigma}(r,r';t) \equiv
of its fluctuations {\delta}n(r, t) = n(r, t) -
n(r, t). These two coarse-grained equations involve a local mobility function
b(r, t) which, in its turn, is written in terms of the memory function of the
two-time correlation function C(r, r' ; t, t') \equiv <{\delta}n(r,
t){\delta}n(r',t')>. For given effective interactions between colloidal
particles and applied external fields, the resulting self-consistent theory is
aimed at describing the evolution of a strongly correlated colloidal liquid
from an initial state with arbitrary mean and covariance n^0(r) and
{\sigma}^0(r,r') towards its equilibrium state characterized by the equilibrium
local concentration profile n^(eq)(r) and equilibrium covariance
{\sigma}^(eq)(r,r').
This theory also provides a general theoretical framework to describe
irreversible processes associated with dynamic arrest transitions, such as
aging, and the effects of spatial heterogeneities
The Wigner function associated to the Rogers-Szego polynomials
We show here that besides the well known Hermite polynomials, the q-deformed
harmonic oscillator algebra admits another function space associated to a
particular family of q-polynomials, namely the Rogers-Szego polynomials. Their
main properties are presented, the associated Wigner function is calculated and
its properties are discussed. It is shown that the angle probability density
obtained from the Wigner function is a well-behaved function defined in the
interval [-Pi,Pi), while the action probability only assumes integer values
greater or equal than zero. It is emphasized the fact that the width of the
angle probability density is governed by the free parameter q characterizing
the polynomial.Comment: 12 pages, 2 (mathemathica) figure
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