The Simons Observatory: metamaterial microwave absorber and its cryogenic applications.

Controlling stray light at millimeter wavelengths requires special optical design and selection of absorptive materials that should be compatible with cryogenic operating environments. While a wide selection of absorptive materials exists, these typically exhibit high indices of refraction and reflect/scatter a significant fraction of light before absorption. For many lower index materials such as commercial microwave absorbers, their applications in cryogenic environments are challenging. In this paper, we present a new tool to control stray light: metamaterial microwave absorber tiles. These tiles comprise an outer metamaterial layer that approximates a lossy gradient index anti-reflection coating. They are fabricated via injection molding commercially available carbon-loaded polyurethane (25% by mass). The injection molding technology enables mass production at low cost. The design of these tiles is presented, along with thermal tests to 1 K. Room temperature optical measurements verify their control of reflectance to less than 1% up to 65∘ angles of incidence, and control of wide angle scattering below 0.01%. The dielectric properties of the bulk carbon-loaded material used in the tiles is also measured at different temperatures, confirming that the material maintains similar dielectric properties down to 3 K.

Evidence of lensing of the cosmic microwave background by dark matter halos.

We present evidence of the gravitational lensing of the cosmic microwave background by 10(13) solar mass dark matter halos. Lensing convergence maps from the Atacama Cosmology Telescope Polarimeter (ACTPol) are stacked at the positions of around 12 000 optically selected CMASS galaxies from the SDSS-III/BOSS survey. The mean lensing signal is consistent with simulated dark matter halo profiles and is favored over a null signal at 3.2σ significance. This result demonstrates the potential of microwave background lensing to probe the dark matter distribution in galaxy group and galaxy cluster halos.

Detection of the power spectrum of cosmic microwave background lensing by the Atacama Cosmology Telescope.

We report the first detection of the gravitational lensing of the cosmic microwave background through a measurement of the four-point correlation function in the temperature maps made by the Atacama Cosmology Telescope. We verify our detection by calculating the levels of potential contaminants and performing a number of null tests. The resulting convergence power spectrum at 2° angular scales measures the amplitude of matter density fluctuations on comoving length scales of around 100 Mpc at redshifts around 0.5 to 3. The measured amplitude of the signal agrees with Lambda cold dark matter cosmology predictions. Since the amplitude of the convergence power spectrum scales as the square of the amplitude of the density fluctuations, the 4σ detection of the lensing signal measures the amplitude of density fluctuations to 12%.

Evidence for dark energy from the cosmic microwave background alone using the Atacama Cosmology Telescope lensing measurements.

For the first time, measurements of the cosmic microwave background radiation (CMB) alone favor cosmologies with w = -1 dark energy over models without dark energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing deflection power spectrum from the Atacama Cosmology Telescope with temperature and polarization power spectra from the Wilkinson Microwave Anisotropy Probe. The lensing data break the geometric degeneracy of different cosmological models with similar CMB temperature power spectra. Our CMB-only measurement of the dark energy density Ω(Λ) confirms other measurements from supernovae, galaxy clusters, and baryon acoustic oscillations, and demonstrates the power of CMB lensing as a new cosmological tool.

When language comprehension reflects production constraints: resolving ambiguities with the help of past experience.

A key assumption in language comprehension is that biases in behavioral data, such as the tendency to interpret John said that Mary left yesterday to mean that yesterday modifies the syntactically local verb left, not the distant verb said, reflect inherent biases in the language comprehension system. In the present article, an alternative production-distribution-comprehension (PDC) account is pursued; this account states that comprehension biases emerge from different interpretation frequencies in the language, which themselves emerge from pressures on the language production system to produce some structures more than others. In two corpus analyses and two self-paced reading experiments, we investigated these claims for verb modification ambiguities, for which phrase length is hypothesized to shape production. The results support claims that tendencies to produce short phrases before long ones create distributional regularities for modification ambiguities in the language and that learning over these regularities shapes comprehenders' interpretations of modification ambiguities. Implications for the PDC and other accounts are discussed.

Correcting the effects of background microcirculation in the measurement of arterial input functions using dynamic susceptibility contrast MRI of the brain.

In dynamic susceptibility contrast MRI, the shape of the arterial input function (AIF) is commonly obtained in the near vicinity of the middle cerebral artery (MCA). However, the tissue regions where the AIF is sampled also have significant perfusion, which contributes to T(2)* changes. We investigate whether correction of this effect will introduce significant changes in the measurement of the AIF and, subsequently, the assessment of the mean transit time (MTT). Clinical dynamic susceptibility data from 13 patients with brain tumors were analyzed. Patients received either single or double doses of Magnevist followed by a saline flush through a power injector. In the correction procedure, DeltaR(2)* was sampled in a region of gray matter approximately 1-2 cm away from the MCA and then subtracted from the DeltaR(2)* sampled in the immediate vicinity of the MCA. We demonstrate that in the brain, this correction of DeltaR(2)* due to tissue perfusion leads to a narrower width of the AIF curve obtained with DeltaR(2)* (mean+/-S.D.=7.3+/-2.0 and 6.4+/-1.7 s, before and after correction, respectively, P<.001 using a two-tailed paired t-test). Furthermore, the peak of the AIF also moved to a slightly earlier time relative to the time of arrival (mean+/-S.D.=4.7+/-0.9 and 4.3+/-0.8 s, before and after correction, with P<.001). With the use of the corrected AIF, the measured MTT had increased values in areas of both gray and white matter.

Late proton MR spectroscopy in children after traumatic brain injury: correlation with cognitive outcomes.

BACKGROUND AND PURPOSE: Proton MR spectroscopy has demonstrated reduced levels of N-acetylaspartate (NAA) in normal-appearing occipital and frontal regions of patients with acute nonpenetrating traumatic brain injury (TBI). We studied the relationship of frontoparietal NAA, choline (Cho), and creatine (Cr) to test the hypothesis that reduction in NAA is predictive of cognitive outcome. METHODS: Proton spectra were collected by using conventional 2D chemical shift imaging in five healthy children and seven children (6 weeks to 3 years) with severe (n=4), moderate (n=2), or mild (n=1) TBI. Spectra in the anterior and posterior regions of the left and right frontoparietal areas were averaged for analysis by using LCModel, with a phantom-established basis function, for quantification of NAA, Cho, and Cr concentrations. Intellectual function, expressive language, and arithmetic capability were measured within 4 months of imaging. RESULTS: NAA/Cho concentration was lower in TBI patients than in control subjects, but no group differences were present for Cho or Cr. Hemispheric levels for NAA, Cho, and Cr were higher on the left than on the right, but we found no effect of region and no interactions. Cognition was lower in the TBI group than the control group and correlated with NAA levels. Left frontal Cho was also correlated with arithmetic scores, whereas Cr was not significantly correlated. CONCLUSION: NAA levels remain low after TBI and are related to cognitive function. Neurometabolite values are greater in the left frontoparietal region than in the right, and the left frontal Cho level is related to arithmetic ability.

Magical Empiricism and 'Exposed Being' in Medicine and Traditional Healing.

Southern African traditional healers often generalize too broadly from discrete ('accidental') instances of success, partly to recruit a clientele, while biomedicine frequently reasons incorrectly from the general to the specific. Both logics are based on empirical observations, but are inversions of each other; these I characterize as 'magical empiricism.' 'Magic' functions as a metapragmatic discourse to recruit a clientele from a skeptical public that doubts the efficacy of any therapeutic interventions, and it acts in parallel with other practical (and efficacious) healing acts. I introduce the concept of 'exposed beings' to describe locally specific constructions of the person as patient and healer. This helps to explain the existence and enduring appeal of many different medical practices and beliefs in South Africa, but I suggest that 'medical parallelism' rather than 'pluralism' might be more accurate.

Development and evaluation of a training program in peer support for former consumers.

While mental health policy in Australia promotes the involvement of mental health consumers in service planning, implementation and evaluation, little has been reported on the training required for the new roles that consumers are being expected to undertake. In this study, 10 former consumers of mental health services participated in a 16-week training program in peer support. The impact of the program on the psychological well-being of the participants was assessed using a battery of self-evaluation questionnaires and focus group interviews. Findings suggest that exposure to people with acute mental health problems (i.e. inpatients), did not, in this instance, adversely impact on the psychological well-being of the participants. Barriers to consumer participation in the mental health field are discussed and recommendations for the content and structure of future consumer peer support training initiatives are proposed.

Innovations in aged care: study tours for Japanese health professionals.

Australian health care management is of increasing interest to Asian organisations, and there have been many advances in the conduct of informative tours. Points to consider when conducting such tours for Japanese visitors are described under the mnemonic STUDY TOURS: Specifications, Translation, Understanding culture, Delivering education, Yen, Timing, Organisation, Unique needs, Residents' values and Safety.

Experience and grammatical agreement: statistical learning shapes number agreement production.

A robust result in research on the production of grammatical agreement is that speakers are more likely to produce an erroneous verb with phrases such as the key to the cabinets, with a singular noun followed by a plural one, than with phrases such as the keys to the cabinet, where a plural noun is followed by a singular. These asymmetries are thought to reflect core language production processes. Previous accounts have attributed error patterns to a syntactic number feature present on plurals but not singulars. An alternative approach is presented in which a process similar to structural priming contributes to the error asymmetry via speakers' past experiences with related agreement constructions. A corpus analysis and two agreement production studies test this account. The results suggest that agreement production is shaped by statistical learning from past language experience. Implications for accounts of agreement are discussed.

Sexual networks and social capital: multiple and concurrent sexual partnerships as a rational response to unstable social networks.

Multiple and concurrent sexual partnerships (MCP) are prevalent in southern Africa and have been identified as a primary cause of high HIV prevalence in this region. Sexual liaisons with multiple partners serve to increase the size and diversity of an individual's sexual-and social-network and therefore to increase their social capital. This maximisation of social capital may minimise the risk to relationship(s) at the cost of maximising the biological risk of HIV infection. Many sexually active individuals appear to neglect their biological risk of HIV infection in order to maximise their 'social capital.' This would seem to be irrational from the perspective of any individual actor, but on a larger social scale, this may give individuals better access to some social and economic goods. The article argues that people who are in unstable and less-connected parts of the sexual network are those most active in building their sexual networks, even where they are not especially promiscuous. However, such strategies may increase exposure to HIV infection in particular populations, such as intravenous drug users, sex workers, and men having sex with men, as well as in the general population of heterosexual southern Africans. What these high HIV-prevalence populations have in common is their participation in sexual-social networks in which individuals try to maximise their social capital by extending the diversity and density of their sexual networks. The discussion shifts analytic attention away from the notion of higher-risk sexual practices of individuals towards consideration for the structure and dynamics of social and sexual networks at a societal level.

Clinical placements in residential aged care facilities: the impact on nursing students' perception of aged care and the effect on career plans.

OBJECTIVES: Undergraduate nursing students have often found clinical placements in aged care unsatisfactory and/or unsettling, dissuading them from considering aged care as an employment option on graduation. This study asked which elements of the clinical placement experience produced that outcome; and what changes could yield more positive outcomes. DESIGN: A descriptive qualitative pilot study was carried out in late 2003. A combination of nominal groups and semi-structured interviews was used with students and experienced nurses to identify commonalities and variations in issues nominated as important and in the views expressed on those issues. Transcripts were independently analysed by two experienced investigators. Themes identified were discussed among the researchers. SUBJECTS: Fourteen volunteer undergraduate nursing students, all of whom had completed clinical placements in residential care and some of whom had prior experience in such facilities, participated in the nominal groups. Twelve registered nurses who had acted as clinical teachers in aged care facilities were interviewed. RESULTS: Perceived issues included: unexamined assumptions about nursing's core skills; lack of pre-placement orientation to the residential care environment; the appeal of and apprehension aroused by autonomous practice; and status, income and career progression considerations. CONCLUSIONS: Analysis of the sometimes ambivalent and conflicting views expressed pointed to possible changes, all within the domain of training and employing institutions, capable of bringing submerged issues to the surface for examination and resolution as part of raising student understanding of gerontology as a demanding specialty and residential care as a rewarding career.

Ultrahigh light transmission through a C-shaped nanoaperture.

Optical resolution beyond the diffraction limit can be achieved by use of a metallic nanoaperture in a near-field optical system. Conventional nanoapertures have very low power throughput. Using a numerical finite-difference time domain method, we discovered a unique C-shaped aperture that provides approximately 3 orders of magnitude more power throughput than a conventional square aperture with a similar near-field spot size of approximately 0.1 lambda. Microwave experiments at 6 GHz quantitatively confirmed the simulated transmission enhancement. The high transmission of the C-aperture--or one of the related shapes--is linked to both a propagation mode in the aperture and local surface plasmons.