Scaling laws for light weight optics, studies of light weight mirrors mounting and dynamic mirror stress, and light weight mirror and mount designs

Scaling laws for light-weight optical systems are examined. A cubic relationship between mirror diameter and weight has been suggested and used by many designers of optical systems as the best description for all light-weight mirrors. A survey of existing light-weight systems in the open literature was made to clarify this issue. Fifty existing optical systems were surveyed with all varieties of light-weight mirrors including glass and beryllium structured mirrors, contoured mirrors, and very thin solid mirrors. These mirrors were then categorized and weight to diameter ratio was plotted to find a best curve for each case. A best fitting curve program tests nineteen different equations and ranks a goodness-to-fit for each of these equations. The resulting relationship found for each light-weight mirror category helps to quantify light-weight optical systems and methods of fabrication and provides comparisons between mirror types

Time walkers and spatial dynamics of ageing information

The distribution of information is essential for living system's ability to coordinate and adapt. Random walkers are often used to model this distribution process and, in doing so, one effectively assumes that information maintains its relevance over time. But the value of information in social and biological systems often decay and must continuously be updated. To capture the spatial dynamics of ageing information, we introduce time walkers. A time walker moves like a random walker, but interacts with traces left by other walkers, some representing older information, some newer. The traces forms a navigable information landscape. We quantify the dynamical properties of time walkers moving on a two-dimensional lattice and the quality of the information landscape generated by their movements. We visualise the self-similar landscape as a river network, and show that searching in this landscape is superior to random searching and scales as the length of loop-erased random walks

Electron diffraction studies of supersonic jets. II. Formation of benzene clusters

Expansions of benzene at 1–10 mol % in neon or helium with various nozzle types have produced clusters of benzene molecules. Preliminary comparisons with intensities from the bulk liquid and with model calculations based on solid state crystal structures suggest that on the average the clusters are probably considerably larger than a 13 molecule unit, and have a vibrational temperature on the order of 100–150 K. Unlike clusters of spherical or quasispherical molecules previously found to pack in nearly crystalline arrays, benzene molecules appear to be unable to organize into regular arrays in the time of our experiments. Local order in clusters is similar but not identical to that in the solid, resembling that expected for a supercooled liquid. The present approach, exploiting several advantages of electron diffraction over alternative methods, shows promise as a new means of studying liquids or glasses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71235/2/JCPSA6-78-1-243-1.pd

Coherent spectroscopy of optical activity

Control of light with light is at the heart of optical information processing. Here we demonstrate for the first time, optical control of light polarization without nonlinearity by exploiting the coherent interaction of light waves on optically active metasurfaces. This polarization effect is ultrafast, compatible with arbitrarily low intensities and offers new opportunities within long-established polarization spectroscopy and sensing techniques

Coherent polarization spectroscopy of metamaterials

We demonstrate control of light polarization with light, without nonlinearity. The manifestation of optical activity in a metasurface is dynamically controlled using the coherent interaction of light waves on the nanostructure to enhance and suppress the light-matter interaction. This enables ultrafast polarization modulation and highly sensitive detection of optical activity

Deoxyephedrine -- mandelic acid diastereomers

Resolution of mandelic acid with (-)(R)-deoxyephedrine in 95% ethanol produces essentially nondiscriminating unsolvated binary mandelate salts. (R)deoxyephedrinium (R)-mandelate (I) is orthorhombic, P212121, a = 8.076(2) Å, b = 8.926(3) Å, c = 23.242(15) Å, V = 1675.3(14) Å3 , Z = 4. (R)-deoxyephedrinium (S)-mandelate (II) is monoclinic, P21, a = 16.061(14) Å, b = 8.902(8) Å, c = 19.585(20) Å, β = 111.76(8)°, V = 2600(4) Å3, Z = 6 with three ionpairs comprising the asymmetric unit. The principle interionic interactions are ribbon-like chains of salt-bridge hydrogen bonds which associate protonated secondary ammonium ions with carboxylates in I and II along crystallographic screw axes with a six-atom repeating unit H-N+-H ··· O-C--O [C22(6)]. The (R)-mandelate additionally shows intraion hydrogen bonding and the (S)-mandelate shows interanion hydrogen bonding. Solubilities (in 95% ethanol), fusion points and heats of fusion indicate essentially no diastereometric discrimination. From acetone, the (S)-mandelate salt forms a efflorescent hemiacetone solvated binary phase (III), triclinic, P1, a = 10.869(9) Å, b = 10.838(13) Å, c = 17.138(18) Å, α = 90.32(9)°, β = 91.34(8)°, γ = 108.20(8)°, V = 1917(4) Å3, Z = 4. Ions form hydrogen bonded chains similar to those in II; acetones are unassociated. In I, columns form with the polar hydrogen bonded chains at the core and nonpolar aryl rings radiating and interdigitating adjacent columns. Packing in II and III produces bilayers of alternating polar and nonpolar regions, with acetones of III in the nonpolar regions

Dispositivos poéticos para nuevos sentidos sobre el trabajo y la cultura

En este trabajo se abordarán algunas prácticas artísticasentendidas como parte de la construcción de procesoscolectivos. De forma particular se trabajará a partir de lasimágenes plasmadas en dos murales realizados en la fachadadel Centro Social y Cultural Olga Vázquez, un espacioautónomo de la ciudad de La Plata. A partir de estas imágenesy poniendo en juego diferentes repertorios poéticos, seexplicitaron concepciones disruptivas sobre el trabajo y lacultura, así como formas de reinstauración del vínculo social yafectivo, ligadas principalmente a nuevas formas políticas ysociales postcrisis del 2001 en Argentina.Se buscará dar cuenta de diferentes aspectos de dichosmurales, quiénes los realizaron y en qué contextos. Por otraparte, serán también abordados a partir de la noción dedispositivo, y en relación con una nueva visualidad urbana, portratarse de imágenes que ocupan los muros externos delinmueble y, de este modo, participan del espacio público

Increasing HIV screening in a secondary hospital emergency department in Brazil: searching for opportunities

Patients seeking emergency care have higher HIV prevalence than the general population, but HIV testing is often not offered in these settings, constituting missed opportunities for HIV testing. Semi structured interviews were conducted withemergency department health workers in a secondary hospital in Brazil. Interviews were recorded, transcribed, and analyzed for themes related to barriers and facilitator to HIV testing in emergency departments (EDs) and strategies to implement HIV screening programs. Currently, most providers reported only offering HIV testing when suspecting that the health problem that motivated the patient to seek care could be HIV-related. Although some providers believed that EDs would not be appropriate to implement screening programs, acceptability of HIV screening programs in this setting was overall high, particularly among nurses. Barriers to increasing HIV testing in EDs included concerns about time, understaffing, and increased costs. The initial triage was identified as a leverage point to obtain consent for HIV screening. Advantages and limitations of HIV screening programs at initial triage, testing blood samples collected for other reasons, and for patients undergoing emergency surgical procedures are discussed. EDs in medium income countries constitute a potential scenario to implement HIV screening programs, and such programs may benefit from empowering nursing staff to that end.Los pacientes que acuden a urgencias presentan una prevalencia del VIH superior a la de la población general, pero a menudo no se ofrecen pruebas del VIH en estos entornos, lo que constituye una pérdida de oportunidades para realizarlas. Se realizaronentrevistas semiestructuradas a trabajadores sanitarios del servicio de urgencias de un hospital secundario de Brasil. Las entrevistas fueron grabadas, transcritas y analizadas en busca de temas relacionados con las barreras y los facilitadores de las pruebas del VIH en los servicios de urgencias (SU) y las estrategias para implementar programas de cribado del VIH. En la actualidad, la mayoría de los proveedores informaron que sólo ofrecen la prueba del VIH cuando sospechan que el problema de salud que motivó al paciente a buscar atención podría estar relacionado con el VIH. Aunque algunos proveedores creían que los SUH no serían apropiados para implementar programas de cribado, la aceptación de los programas de cribado del VIH en este entorno era en general alta, especialmente entre las enfermeras. Los obstáculos para aumentar las pruebas del VIH en los SUH incluían la preocupación por el tiempo, la falta de personal y el aumento de los costes. El triaje inicial se identificó como un punto de apoyo para obtener el consentimiento para el cribado del VIH. Se discuten las ventajas y limitaciones de los programas de cribado del VIH en el triaje inicial, el análisis de muestras de sangre recogidas por otras razones, y para los pacientes sometidos a procedimientos quirúrgicos de emergencia. Los SUH de países de renta media constituyen un escenario potencial para implementar programas de cribado del VIH, y dichos programas pueden beneficiarse de la capacitación del personal de enfermería para tal fin.Os pacientes que procuram atendimento de emergência têm maior prevalência de HIV do que a população em geral, mas o teste de HIV muitas vezes não é oferecido nesses ambientes, o que constitui oportunidades perdidas para o teste de HIV. Foram realizadas entrevistas semiestruturadas com profissionais de saúde do departamento de emergência em um hospital secundário no Brasil. As entrevistas foram gravadas, transcritas e analisadas quanto a temas relacionados a barreiras e facilitadores do teste de HIV em departamentos de emergência (EDs) e estratégias para implementar programas de triagem de HIV. Atualmente, a maioria dos provedores relatou que só oferece testes de HIV quando suspeita que o problema de saúde que motivou o paciente a procurar atendimento pode estar relacionado ao HIV. Embora alguns provedores acreditassem que os departamentos de emergência não seriam apropriados para implementar programas de triagem, a aceitabilidade dos programas de triagem de HIV nesse ambiente foi, em geral, alta, especialmente entre os enfermeiros. As barreiras para aumentar os testes de HIV nos DEs incluíam preocupações com o tempo, falta de pessoal e aumento dos custos. A triagem inicial foi identificada como um ponto de alavancagem para obter o consentimento para a triagem de HIV. São discutidas as vantagens e as limitações dos programas de triagem de HIV na triagem inicial, no teste de amostras de sangue coletadas por outros motivos e para pacientes submetidos a procedimentos cirúrgicos de emergência. As salas de emergência em países de renda média constituem um cenário em potencial para a implementação de programas de triagem de HIV, e esses programas podem se beneficiar da capacitação da equipe de enfermagem para esse fim

Decoherence by electromagnetic fluctuations in double-quantum-dot charge qubits

We discuss decoherence due to electromagnetic fluctuations in charge qubits formed by two lateral quantum dots. We use an effective circuit model to evaluate correlations of voltage fluctuations in the qubit setup. These correlations allows us to estimate energy (T1) and phase (T2) relaxation times of the the qubit system. Our theoretical estimate of the quality factor due to dephasing by electromagnetic fluctuations yields values much higher than those found in recent experiments, indicating that other sources of decoherence play a dominant role.Comment: 12 pages, 5 figure