Image formation by manipulation of the entangled angular spectrum

We demonstrate theoretical and experimentally how it is possible to manipulate an entangled angular spectrum of twin beams, in order to reconstruct correlated images with coincidence detection. The entangled angular spectrum comes from the pump and the image is obtained only if signal and idler are properly treated.Comment: Submitted for publication in Optics Communication

Measurement of focusing properties for high numerical aperture optics using an automated submicron beamprofiler

The focusing properties of three aspheric lenses with numerical aperture (NA) between 0.53 and 0.68 were directly measured using an interferometrically referenced scanning knife-edge beam profiler with sub-micron resolution. The results obtained for two of the three lenses tested were in agreement with paraxial gaussian beam theory. It was also found that the highest NA aspheric lens which was designed for 830nm was not diffraction limited at 633nm. This process was automated using motorized translation stages and provides a direct method for testing the design specifications of high numerical aperture optics.Comment: 6 pages 4 figure

Sub-Pixel Response Measurement of Near-Infrared Sensors

Wide-field survey instruments are used to efficiently observe large regions of the sky. To achieve the necessary field of view, and to provide a higher signal-to-noise ratio for faint sources, many modern instruments are undersampled. However, precision photometry with undersampled imagers requires a detailed understanding of the sensitivity variations on a scale much smaller than a pixel. To address this, a near-infrared spot projection system has been developed to precisely characterize near-infrared focal plane arrays and to study the effect of sub-pixel non uniformity on precision photometry. Measurements of large format near-infrared detectors demonstrate the power of this system for understanding sub-pixel response.Comment: 9 pages, 13 figures, submitted to PAS

Tension Propagation Along Tip-Link Cadherins: Regulation and Implications for the Auditory System

Hair bundles detect sound by shearing in response to vibrations spanning orders of magnitude in intensity and frequency. Their responsiveness stems from mechanosensitive ion channels that sit atop the stereocilia and are gated by tension in tip links. Experimental evidence and theoretical arguments implicate a soft compliant element, with a stiffness of 1-4 mN/m, as necessary for mechanotransduction. Although the identity of this element remains an open question, direct measurements of a component of the tip link have highlighted entropic elasticity as one relevant characteristic. A tip link comprises a heterotetremer of protocadherin-15 and cadherin-23, arranged in a loose helical configuration and joined at their amino-terminals through a calcium ion dependent interaction. As for many other biopolymers, the tip link’s stiffness is several times greater than that of the empirically measured gating spring. To remain a viable candidate as a compliant element, entropic elasticity in the tip link must therefore be shown to support the full frequency and intensity range of auditory stimuli. In the present work, we model the tip link as a worm-like chain and evaluate its fast dynamic response using theoretical and numerical calculations. Our analysis uncovers frequencies at which the tip link exhibits viscoelastic behavior, and we evaluate how this behavior might alter auditory function. Critical to modulating the tip link’s frequency-dependent response is the resting tension, which controls both the frequency above which the tip link behaves viscoelastically and the tip-link’s local nonlinear stiffness. Under low resting tensions, we find that tension pools at the ends of the tip link and propagates poorly into the bulk of the chain. Upon application of high resting tensions, the frequency above which the tip link shows non-equilibrium behavior shifts beyond the range of human hearing

Complete Calabi-Yau metrics from smoothing Calabi-Yau complete intersections

We construct complete Calabi-Yau metrics on non-compact manifolds that are smoothings of an initial complete intersection $V_0$ that is a Calabi-Yau cone, extending the work of Sz\'ekelyhidi (2019). The constructed Calabi-Yau manifold has tangent cone at infinity given by $\mathbb{C} \times V_0$. This construction produces Calabi-Yau metrics with fibers having varying complex structures and possibly isolated singularities.Comment: Published version in Geometriae Dedicat

Roots of Conflict: A Multi-level Analysis of the South Atlantic War of 1982

On 2 April 1982, the Argentinian military had invaded and occupied a series of islands known as the Islas Malvinas, or Falkland Islands.* Subsequently, The United Kingdom had responded with a counter-invasion and occupation in an effort to deny the Argentinian claim of sovereignty over the archipelago. After nearly two months and combat casualties in excess of a thousand soldiers the British military was able to negate the Argentinian success and assert its ownsovereignty over the disputed territories. While the outcome of the dispute is clear, the impetus for its initiation is somewhat murky. This paper will attempt to highlight the various theoretical arguments that claim to explain the origin of the crisis. In order to accomplish this task, several levels of analysis will be explored. Such an approach will look at the individual, group, state, and systemic explanations of the conflict. * The terms Falkland Islands (the British term) and Islas Malvinas (the Argentinian term) are hereinafter referenced in a combined fashion as the Falklands/Malvinas. The war itself will be referenced in a neutral fashion as the South Atlantic War

Sub-wavelength terahertz beam profiling of a THz source via an all-optical knife-edge technique

Terahertz technologies recently emerged as outstanding candidates for a variety of applications in such sectors as security, biomedical, pharmaceutical, aero spatial, etc. Imaging the terahertz field, however, still remains a challenge, particularly when sub-wavelength resolutions are involved. Here we demonstrate an all-optical technique for the terahertz near-field imaging directly at the source plane. A thin layer (<100 nm-thickness) of photo carriers is induced on the surface of the terahertz generation crystal, which acts as an all-optical, virtual blade for terahertz near-field imaging via a knife-edge technique. Remarkably, and in spite of the fact that the proposed approach does not require any mechanical probe, such as tips or apertures, we are able to demonstrate the imaging of a terahertz source with deeply sub-wavelength features (<30 μm) directly in its emission plane

Failure to adapt; Intelligence Failure and Military Failure as Functions of Strategic Failure?

The following paper looks at intelligence failures and military failures through the lens of adaptation failure. This paper asserts that there is reason to believe that certain causal elements of alleged intelligence failures reside more so in the province of politics, than in the collection and analysis domain of intelligence tradecraft. This is not to say that failures are exclusively of a political nature, but that looking at politics and the relationship of policymakers to the Intelligence Community yields a preponderance of causal evidence. Secondly, it is suggested that a parallel set of underlying assumptions evident in adaptation failure theory may be observed in military failures as well. This leads to the final analysis, which tends to suggest that it is anything but final and therefore may be indicative of a superordinate realm: strategic failure

Evolutions in Suicide Bombing: Exploring the Relationship Between the Tactic and Its Application by Non-state Armed Groups Across Various Conflict Zones Over Time

The following dissertation considers variations in the use of suicide bombing by Non-State Armed Groups (NSAGs), at the organizational level of analysis. It is both a quantitative and qualitative assessment of the conditions under which insurgents that accept the practice’s legitimacy have applied it to a range of specified target sets. The broad focus of this endeavor centers on unpacking insurgent groups’ behaviors across a number of unique battlespaces, but the main question I seek to answer is: what decision dynamics accompany violent non-state actors’ use of suicide bombing and how do we interpret their behavioral interaction across various conflict zones, so as to better illuminate why they continue to attack in this way? Put differently, what does suicide bombing, as an operational-level tactic as opposed to a presumably fully developed strategy, reveal about NSAGs who use it? I also explore a more narrowly tailored sub-set of questions that aim to uncover why insurgents that do use it, do so in different ways, which also entails an analysis of non-suicide bombing attacks against the same range of target sets. To that end, I explore the ways suicide bombing is used by several organizations, within a variety of combat venues, as a means for better understanding its uses; namely, adapting to and shaping, unique battlespaces. I find that organizations such as al-Qa’ida (AQ) are more sensitive to branding/re-branding dynamics associated with the targeting of civilians, while others such as Islamic State (IS) incorporate suicide bombing as a key component of their war arsenal against civilian, security, and competitor target sets. This may explain why it generally tended to be the case in multiple venues that AQ didn’t practice suicide bombing against IS, but IS did so against AQ. The exploratory nature of my work can be seen in the methodological approach I take, which extracts data points and re-forms them as variables that can be scrutinized further. This has implications for policy, theory, and epistemology. In policy terms, I elucidate the need to consider suicide bombing as an instrumental means for achieving objectives that are positioned below the threshold of a fully developed strategy. Theoretically, in contrast to a leading explanation for the practice, I am able to say with some confidence that the presence of foreign militaries has had little to no impact on the use of suicide bombing. Epistemologically, disaggregating target types, based on the dataset’s existing narratives, is a viable path for better understanding how suicide bombing violence is used by non-state actors