Pointing Analysis and Design Drivers for Low Earth Orbit Satellite Quantum Key Distribution

The world relies on encryption to perform critical and sensitive tasks every day. If quantum computing matures, the capability to decode keys and decrypt messages becomes possible. Quantum key distribution (QKD) is a method of distributing secure cryptographic keys which relies on the laws of quantum mechanics. Current implementations of QKD use fiber-based channels which limit the number of users and the distance between users. Satellite-based QKD using free-space channels is proposed as a feasible secure global communication solution. Since a free-space link does not use a waveguide, pointing a transmitter to receiver is required to ensure signal arrival. In this thesis, a scenario consisting of five ground sites is used to compare the amount of raw key material that can be received from four different orbits when perfect pointing is assumed. A second scenario utilizing one ground site is used to model the effect of pointing accuracy for the four orbits. The data from the first scenario indicates that lower altitudes produce higher key rates and sun-synchronous orbits don’t always produce the longest or most consistent keys. Data from the second scenario reveals a pointing bias of 1.3 μrad or less is most desirable and that with 1.3 μrad of pointing bias, a pointing jitter of 0.4 μrad will have no significant effect on key rates

Growth and Characterization of Gold Nanostructures Produced from Diatomaceous Algae

Silica nanostructures (frustules) grown by the algae Thalassiosira eccentrica can be used to template the production of regular arrays of supported gold nanodots, with sizes ranging from 30 to 50 nm. This growth is of particular interest because it represents a novel and efficient way to produce and distribute nanoparticles, particularly for applications in catalysis, and may demonstrate a value for a byproduct ash produced when diatomaceous algae is used to produce biofuel. Growth has been characterized by both SEM and AFM imagery. This growth of regular nanoparticles has also been demonstrated with carbon evaporation, and may be a means to produce similar structures using a diversity of materials. This research explores the explanation, replication, and potential applications of this phenomenon

Polarization-controlled single photons

Vacuum-stimulated Raman transitions are driven between two magnetic substates of a rubidium-87 atom strongly coupled to an optical cavity. A magnetic field lifts the degeneracy of these states, and the atom is alternately exposed to laser pulses of two different frequencies. This produces a stream of single photons with alternating circular polarization in a predetermined spatio-temporal mode. MHz repetition rates are possible as no recycling of the atom between photon generations is required. Photon indistinguishability is tested by time-resolved two-photon interference.Comment: 4 pages, 3 figure

Local texture and percolative paths for long-range conduction in high critical current density TlBa₂Ca₂Cu₃O₈₊ₓ deposits

©1994 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: http://link.aip.org/link/?APPLAB/64/106/1DOI:10.1063/1.110908A possible microstructural origin of the high critical current densities which have been obtained in c-axis-aligned, polycrystalline TlBa₂Ca₂Cu₃O₈₊ₓdeposits has been identified. The results of x-ray diffraction determinations of basal plane texture of Tl-1223 deposits prepared by spray pyrolysis are observed to depend on the size of the x-ray beam. Furthermore, most grain boundaries were found from transmission electron microscopy to have small misorientation angles. It is concluded that although overall the basal plane orientations are nearly random, there is a high degree of local texture indicative of colonies of similarly oriented grains. The spread in a-axis orientation within a colony is ~10°–15°. Intercolony conduction, it is suggested, may be enhanced by a percolative network of small-angle grain boundaries at colony interfaces

Predictors of Teacher Efficacy for Inclusive Practice in Pre-service Teachers

Teachers who show high teacher efficacy affect student achievement positively. Teaching is sometimes seen as an overwhelming profession because of classroom diversity and expectations placed on teachers. It is important to bring beginning teachers to the point at which they feel they are capable and will be more emotionally equipped to take on the stressors of the classroom. The current study focused on predicting pre-service teachers’ efficacy for inclusive practice from variables found to be important in the literature: gender, inclusion-related beliefs, and experiences with individuals with disabilities. Participants consisted of 1,026 students completing the in-faculty component of their pre-service program in 9 faculties of education across Canada. They completed the Teacher Efficacy for Inclusive Practice survey and the Beliefs about Learning and Teaching Questionnaire. All teacher candidates appeared to benefit from experience with people with disabilities. General findings indicated more positive inclusive beliefs for women than men and for pre-service teachers in elementary than in secondary programs. Important differences emerged, however, concerning which beliefs contributed to each area of teacher efficacy for secondary as compared to elementary programs. Results are discussed in terms of issues to consider in initial teacher education programs

Mariposas em parreirais na região da Serra Gaúcha e informações sobre espécies com potencial para perfurar frutos.

Esta Circular Técnica apresenta informações sobre as mariposas registradas nos parreirais, bem como suas características morfológicas e biológicas, visando orientar técnicos e produtores quanto ao manejo que pode ser adotado nas áreas com presença desses insetos.bitstream/item/62488/1/cir089.pd

Immature stages of Spodoptera eridania (Lepidoptera: noctuidae): developmental parameters and host plants.

This study aimed to detail the temporal and morphological parameters of the immature stages of southern armyworm Spodoptera eridania (Stoll, 1782) with larvae feed on artificial diet, under controlled conditions (25?±?1°C, 70?±?10% relative humidity and 14-h photophase) and gather information about their larval host plants. The viability of the egg, larval, pupal, and prepupal stages was 97.82, 93.62, 96.42, and 97.03%, respectively. The average duration of the egg, larval, pupal, and pre-pupal stages was 4.00, 16.18, 1.58, and 9.17 d, respectively. During the larval stage, 43.44% of females passed through seven instars, observing that the female's development was significant slower than males. The female larvae that developed through six and seven instars exhibited a mean growth rate of 1.52 and 1.44, respectively. Female pupae were significantly larger, exhibiting faster development than males. The rearing method proved to be adequate, providing more detailed observations of the biological cycle, especially at the larval stage, and resulting in an overall survival of almost 85%. Two hundred two plant species belonging to 58 families are listed as natural hosts for S. eridania, mainly including Asteraceae, Fabaceae, Solanaceae, Poaceae, Amaranthaceae, and Malvaceae

Cell wall chitosan is necessary for virulence in the opportunistic pathogen Cryptococcus neoformans

Cryptococcus neoformans is an opportunistic fungal pathogen that causes meningoencephalitis. Its cell wall is composed of glucans, proteins, chitin, and chitosan. Multiple genetic approaches have defined a chitosan-deficient syndrome that includes slow growth and decreased cell integrity. Here we demonstrate chitosan is necessary for virulence and persistence in the mammalian host

Mechanical Behavior of Mushy Zone in DC casting using a Viscoplastic Material Model

Direct Chill (DC) casting is a semi-continuous metal manufacturing process for producing non-ferrous alloys such as aluminum and magnesium. During the solidification of the alloy, there exists a semi-solid state of material known as mushy zone which is more prone to hot tearing. Precise modeling of hot tearing is the most challenging task due to the interaction of many physical fields. The deformation of the partially coherent solid strongly influences the hot cracking. This work focuses on the material behavior of the mushy zone which is the prerequisite for the development of hot tearing criteria. The rate-dependent nature plays a crucial role at higher temperatures. Therefore, the viscoplastic material models with temperature-dependent coefficients are implemented for the characterization of the mushy zone. The numerical integration of the constitute equations are explained in detail. The liquid flow is neglected, and the momentum and energy equations are solved for the mushy and solid phases. With the help of a viscoplastic material models, the stress and strain evolution in the mushy zone is captured. It is found that the state of stress in mushy region is tensile in nature which is a favorable situation for the hot cracks. The influence of the casting speed and secondary cooling on the mushy stress state are analyzed in detail