Arbitrary beam control using passive lossless metasurfaces enabled by orthogonally-polarized custom surface waves

For passive, lossless impenetrable metasurfaces, a design technique for arbitrary beam control of receiving, guiding, and launching is presented. Arbitrary control is enabled by a custom surface wave in an orthogonal polarization such that its addition to the incident (input) and the desired scattered (output) fields is supported by a reactive surface impedance everywhere on the reflecting surface. Such a custom surface wave (SW) takes the form of an evanescent wave propagating along the surface with a spatially varying envelope. A growing SW appears when an illuminating beam is received. The SW amplitude stays constant when power is guided along the surface. The amplitude diminishes as a propagating wave (PW) is launched from the surface as a leaky wave. The resulting reactive tensor impedance profile may be realized as an array of anisotropic metallic resonators printed on a grounded dielectric substrate. Illustrative design examples of a Gaussian beam translator-reflector, a probe-fed beam launcher, and a near-field focusing lens are provided

Functional metasurfaces: Do we need normal polarizations?

We consider reciprocal metasurfaces with engineered reflection and transmission coefficients and study the role of normal (with respect to the metasurface plane) electric and magnetic polarizations on the possibilities to shape the reflection and transmission responses. We demonstrate in general and on a representative example that the presence of normal components of the polarization vectors does not add extra degrees of freedom in engineering the reflection and transmission characteristics of metasurfaces. Furthermore, we discuss advantages and disadvantages of equivalent volumetric and fully planar realizations of the same properties of functional metasurfaces.Comment: 3 pages, 2 figures, XXXIInd International Union of Radio Science General Assembly and Scientific Symposium, paper B7-1, pp. 1-3, Montreal, Canada, 19-26 August 2017 (invited

Skyrmions and Anomalous Hall Effect in a Dzyloshinskii-Moriya Spiral Magnet

Monte Carlo simulation study of a classical spin model with Dzylosinskii-Moriya interaction and the spin anisotropy under the magnetic field is presented. We found a rich phase diagram containing the multiple spin spiral (or skyrme crystal) phases of square, rectangular, and hexagonal symmetries in addition to the spiral spin state. The Hall conductivity $\sigma_{xy}$ is calculated within the $sd$ model for each of the phases. While $\sigma_{xy}$ is zero in the absence of external magnetic field, applying a field strength $H$ larger than a threshold value $H_c$ leads to the simultaneous onset of nonzero chirality and Hall conductivity. We find $H_c = 0$ for the multiple spin spiral states, but $H_c > 0$ for a single spin spiral state regardless of the field orientation. Relevance of the present results to MnSi is discussed

Identification of antigen-presenting dendritic cells in mouse aorta and cardiac valves

Presumptive dendritic cells (DCs) bearing the CD11c integrin and other markers have previously been identified in normal mouse and human aorta. We used CD11c promoter-enhanced yellow fluorescent protein (EYFP) transgenic mice to visualize aortic DCs and study their antigen-presenting capacity. Stellate EYFP + cells were readily identified in the aorta and could be double labeled with antibodies to CD11c and antigen-presenting major histo-compatability complex (MHC) II products. The DCs proved to be particularly abundant in the cardiac valves and aortic sinus. In all aortic locations, the CD11c + cells localized to the subintimal space with occasional processes probing the vascular lumen. Aortic DCs expressed little CD40 but expressed low levels of CD1d, CD80, and CD86. In studies of antigen presentation, DCs selected on the basis of EYFP expression or binding of anti-CD11c antibody were as effective as DCs similarly elected from the spleen. In particular, the aortic DCs could cross-present two different protein antigens on MHC class I to CD8 + TCR transgenic T cells. In addition, after intravenous injection, aortic DCs could capture anti-CD11c antibody and cross-present ovalbumin to T cells. These results indicate that bona fide DCs are a constituent of the normal aorta and cardiac valves

Characteristics and treatments of large cystic brain metastasis: radiosurgery and stereotactic aspiration.

Brain metastasis represents one of the most common causes of intracranial tumors in adults, and the incidence of brain metastasis continues to rise due to the increasing survival of cancer patients. Yet, the development of cystic brain metastasis remains a relatively rare occurrence. In this review, we describe the characteristics of cystic brain metastasis and evaluate the combined use of stereotactic aspiration and radiosurgery in treating large cystic brain metastasis. The results of several studies show that stereotactic radiosurgery produces comparable local tumor control and survival rates as other surgery protocols. When the size of the tumor interferes with radiosurgery, stereotactic aspiration of the metastasis should be considered to reduce the target volume as well as decreasing the chance of radiation induced necrosis and providing symptomatic relief from mass effect. The combined use of stereotactic aspiration and radiosurgery has strong implications in improving patient outcomes

‘By prophesying to the wind, the wind came and the dry bones lived’: John Eliot’s puritan ministry to New England Indians

John Eliot (1604-1690) has been called ‘the apostle to the Indians’. This thesis looks at Eliot not from the perspective of modern Protestant ‘mission’ studies (the approach mainly adopted by previous research) but in the historical and theological context of 17th century puritanism. Drawing on recent research on migration to New England, the thesis argues that Eliot, like many other migrants, went to New England primarily in search of a safe haven to practise pure reformed Christianity, not to convert Indians. Eliot’s Indian ministry started from a fundamental concern for the conversion of the unconverted, which he derived from his experience of the puritan movement in England. Consequently, for Eliot, the notion of New England Indian ‘mission’ was essentially conversion-oriented, Wordcentred, and pastorally focussed, and (in common with the broader aims of New England churches) pursued a pure reformed Christianity. Eliot hoped to achieve this through the establishment of Praying Towns organised on a biblical model – where preaching, pastoral care and the practice of piety could lead to conversion – leading to the formation of Indian churches composed of ‘sincere converts’. The thesis starts with a critical historiographical reflection on how missiologists deploy the term ‘mission’, and proposes a perspectival shift for a better understanding of Eliot (Chapter 1). The groundwork for this new perspective is laid by looking at key themes in recent scholarship on puritanism, focusing on motives for the Great Migration, millenarian beliefs, and the desire for Indian conversion (Chapter 2). This chapter concludes that Indian conversion and millenarianism were not the main motives for Eliot’s migration to the New World, nor were his thoughts on the millennium an initial or lasting motive for Indian ministry. Next, the thesis investigates Eliot’s historical and theological context as a minister, through the ideas of puritan contemporaries in Old and New England, and presents a new perspective on Eliot by suggesting that conversion theology and pastoral theology were the most fundamental and lasting motives for his Indian ministry (Chapter 3). After the first three chapters, which relocate Eliot in his historical context, the last three chapters consider Eliot’s pastoral activities with the Indians. These have usually been understood as ‘mission’, without sufficient understanding of Eliot’s historical and theological context in the puritan movement and how he applied its ideas to Indian ministry. The thesis examines Eliot’s views on ‘Praying Towns’ as settlements for promoting civility and religion, and ‘Indian churches’ as congregations of true believers formed by covenant (Chapter 4). It investigates Eliot’s activities in the Indian communities, to apply puritan theology and ministerial practice to the Indians as his new parishioners (Chapter 5). Finally, the thesis offers a comparison of puritan and Indian conversion narratives, to try to recover Praying Indians’ own voices about conversion and faith (Chapter 6). This analysis finds both similarities and differences. The extent of the similarities does not necessarily mean (as some have alleged) that puritanism was unilaterally imposed on the Indians. The evidence equally well suggests a nuanced picture of Eliot’s engagement with the Indians from the perspective of 17th century puritanism and its conversion-oriented parish ministry