Probing ice-nucleation processes on the molecular level using second harmonic generation spectroscopy

We present and characterize a novel setup to apply Second Harmonic Generation (SHG) spectroscopy in total internal reflection geometry (TIR) to heterogeneous freezing research. It allows to monitor the evolution of water structuring at solid surfaces at low temperatures prior to heterogeneous ice nucleation. Apart from the possibility of investigating temperature dependence, a major novelty in our setup is the ability of measuring sheet-like samples in TIR geometry in a direct way. As a main experimental result, we find that our method can discriminate between good and poor ice nucleating surfaces. While at the sapphire basal plane, which is known to be a poor ice nucleator, no structural rearrangement of the water molecules is found prior to freezing, the basal plane surface of mica, an analogue to ice active mineral dust surfaces, exhibits a strong change in the nonlinear optical properties at temperatures well above the freezing transition. This is interpreted as a pre-activation, i.e. an increase in the local ordering of the interfacial water which is expected to facilitate the crystallization of ice at the surface. The results are in line with recent predictions by Molecular Dynamics simulations on a similar system

Between tradition and modernity: determining spatial systems of privacy in the domestic architecture of contemporary Iraq

The notion of privacy represents a central criterion for both indoor and outdoor social spaces in most traditional Arab settlements. This paper investigates privacy and everyday life as determinants of the physical properties of the built and urban fabric and will study their impact on traditional settlements and architecture of the home in the contemporary Iraqi city. It illustrates the relationship between socio-cultural aspects of public/private realms using the notion of the social sphere as an investigative tool of the concept of social space in Iraqi houses and local communities (Mahalla). This paper reports that in spite of the impact of other factors in articulating built forms, privacy embodies the primary role under the effects of Islamic rules, principles and culture. The crucial problem is the underestimation of traditional inherited values through opening social spaces to the outside that giving unlimited accesses to the indoor social environment creating many problems with regard to privacy and communal social integration

Public Health Impact of Extremely Low-Frequency Electromagnetic Fields

INTRODUCTION: The association between exposure to extremely low-frequency electric and magnetic fields (ELF) and childhood leukemia has led to the classification of magnetic fields by the International Agency for Research on Cancer as a “possible human carcinogen.” This association is regarded as the critical effect in risk assessment. Creating effective policy in light of widespread exposure and the undisputed value of safe, reliable, and economic electricity to society is difficult and requires estimates of the potential public health impact and associated uncertainties. OBJECTIVES: Although a causal relationship between magnetic fields and childhood leukemia has not been established, we present estimates of the possible pubic health impact using attributable fractions to provide a potentially useful input into policy analysis under different scenarios. METHODS: Using ELF exposure distributions from various countries and dose–response functions from two pooled analyses, we calculate country-specific and worldwide estimates of attributable fractions (AFs) and attributable cases. RESULTS: Even given a wide range of assumptions, we find that the AF remains < 10%, with point estimates ranging from < 1% to about 4%. For small countries with low exposure, the number of attributable cases is less than one extra case per year. Worldwide the range is from 100 to 2,400 cases possibly attributable to ELF exposure. CONCLUSION: The fraction of childhood leukemia cases possibly attributable to ELF exposure across the globe appears to be small. There remain, however, a number of uncertainties in these AF estimates, particularly in the exposure distributions

Virtual platforms for heritage preservation in the Middle East: the case of medieval Cairo

Much of the effort in VH is directed towards accurate representation of historic structures, objects or artefacts. There is little attention is paid, however, to the human aspects of city life, the intangible heritage to which people can actually relate. Digital models of historic buildings and spaces only give a sense of precision. Yet, rituals, human attitude and cultural traditions remained a gap in current research and advanced technology in heritage visualization. Virtual Heritage Environments (VHE) suffer from the lack of ‘thematic interactivity’ due to the limited cultural content and engaging modules largely used in photorealistic video gaming systems. In order to approach virtual fidelity and accurate reproduction of historic environments, this paper reports on a research process to investigate and incorporate a Cultural-feed into digital platforms of Virtual Heritage. In doing so, the paper focuses on the Middle East in general and Medieval Cairo in particular. It discusses conceptual and practical framework for the development of virtual heritage platforms as a research, educational and engagement tool that brings historic spaces and buildings back to the recognition of the public eye of the ordinary user. It analyses current practices and projects of the virtual heritage technologies and reports on field work that took place in Islamic Cairo with Five Start-Up entrepreneurs

Contested heritage: an analysis of the physical transformation of Derry/Londonderry’s siege monument

Transformations of Derry/Londonderry’s medieval city walls during the twentieth century have shaped an urbanism of segregated settlements within a city of religious confrontation. The heritage of military blockades, peace lines and watchtowers imposed upon the city’s Walls has influenced the disintegration of public space and created areas of no man’s land around the peripheries of the monument. The aim of this paper is to examine physical transformation and trace the consequences of urban planning regarding the historic city Walls. This change includes the shifting of residential settlements in the Bogside/Fountain areas and the movement of Protestant settlements towards the Waterside of Derry/Londonderry. The history and heritage of the Walls are analysed by focusing on four periods: 1600, when the first medieval walls were constructed; the housing crisis of 1948; the 1968 urban area plan and the beginning of the ‘Troubles’; and the present day. This analysis offers an understanding of the spatial relationships between enclaves and the monument over key moments of conflict and political change. The paper reveals that the manifestations of the Walls have aided in the further division of religiously segregated communities in Derry/Londonderry

Aging behavior of intercritically quenched ductile iron

Although extensive aging and strain aging (bake hardening, BH) studies have been carried out on dual-phase steels, the aging behavior of the dual matrix structure (DMS) ductile iron (DI), as a potential way to improve its mechanical properties, has not been addressed until now. This research was designed to study the aging behavior of DI with a ferrite-martensite matrix structure. DMS-DI with a martensite volume fraction of 30% was produced by intercritical austenitizing at 785 ◦C followed by quenching in water to room temperature. Aging treatments were carried out without prestraining at aging temperatures of 140, 170, and 220 ◦C for 2–10,000 min. DMS-DI was investigated by light optical microscopy (LOM) for unaged samples and scanning electron microscopy (SEM) for selected samples after aging treatments. The effect of aging conditions on the mechanical properties were investigated. Microhardness measurements for ferrite and martensite were also examined as a function of aging conditions. The increase in yield strength due to aging was determined. The results indicate that the aging conditions have a small effect on the ultimate tensile strength UTS. It is shown that the yield strength increased to a maximum value of 45 MPa (~11% increase) after aging for particular time, which is found to be dependent on the aging temperature. The peak aging response is followed by a decrease in yield strength, which is observed to be attributed to martensite tempering as confirmed by microhardness measurements

Taming the Yukawa potential singularity: improved evaluation of bound states and resonance energies

Using the tools of the J-matrix method, we absorb the 1/r singularity of the Yukawa potential in the reference Hamiltonian, which is handled analytically. The remaining part, which is bound and regular everywhere, is treated by an efficient numerical scheme in a suitable basis using Gauss quadrature approximation. Analysis of resonance energies and bound states spectrum is performed using the complex scaling method, where we show their trajectories in the complex energy plane and demonstrate the remarkable fact that bound states cross over into resonance states by varying the potential parameters.Comment: 8 pages, 2 tables, 1 figure. 2 mpg videos and 1 pdf table file are available upon request from the corresponding Autho

Vertical Macular Asymmetry Measures Derived From SD-OCT for Detection of Early Glaucoma.

PurposeTo test the hypothesis that vertical asymmetry in macular ganglion cell/inner plexiform layer (GCIPL) thickness can improve detection of early glaucoma.MethodsSixty-nine normal eyes and 101 glaucoma eyes had macular imaging with spectral-domain optical coherence tomography (OCT; 200 × 200 cube). The resulting GCIPL thickness matrix was grouped into a 20 × 20 superpixel array and superior superpixels were compared to their inferior counterparts. A global asymmetry index (AI) was defined as the grand mean of the asymmetry ratios. To measure local asymmetry, the corresponding thickness measurements of three rows above and below the horizontal raphe were compared individually and in combinations. Global and local AIs were compared to the best-performing GCIPL thickness parameters with area under the receiver operating curves (AUC) and sensitivity/specificities.ResultsAge or axial length did not influence AIs in normal subjects (P ≥ 0.08). Global and local AIs were significantly higher in the glaucoma group compared to normal eyes. Minimum (AUC = 0.962, 95% confidence interval [CI]: 0.936-0.989) and inferotemporal thickness (AUC = 0.944, 95% CI: 0.910-0.977; P = 0.122) performed best for detection of early glaucoma. The AUC for global AI was 0.851 (95% CI: 0.792-0.909) compared to 0.916 (95% CI: 0.874-0.958) for the best local AI. Combining minimum or inferotemporal GCIPL thickness and the best local AI led to higher partial AUCs (0.088 and 0.085, 90% specificity, P = 0.120 and 0.130, respectively) than GCIPL thickness measures.ConclusionsMacular vertical thickness asymmetry measures did not perform better than sectoral or minimum GCIPL thickness for detection of early glaucoma. Combining local asymmetry parameters with the best sectoral GCIPL thickness measures enhanced this task