Iron(II) complexes containing the 2,6-bis-iminopyridyl moiety : synthesis, characterization, reactivity, and DNA binding

Two iron(II) complexes, [FeII(pytBuN3)2](FeCl4) (1) and [FeII(pytBuMe2N3)Cl2] (2), with sterically constrained pytBuN3 and pytBuMe2N3 chelate ligands (pytBuN3 = 2,6-bis-(aldiimino)pyridyl; pytBuMe2N3 = 2,6-bis-(ketimino)pyridyl), have been synthesized and characterized by elemental analysis, IR, UV–vis spectra, and preliminary X-ray single-crystal diffraction. The latter revealed that Fe(II) in 1 is six-coordinate by six nitrogen donors from two bisiminopyridines in a distorted octahedron. Complex 2 reacts with thiourea with a second-order rate constant k2 = (2.50 ± 0.05) × 10−3 M−1 s−1 at 296 K, and the reaction seemed to be slow. In a similar way, the interaction of 2 and DNA was studied by fluorescence and absorption spectroscopy. The results revealed that 2 caused fluorescence quenching of DNA through a dynamic quenching procedure. The binding constants KA, Kapp, and KSV as well as the number of binding sites between 2 and DNA were determined

Resilience as a communal concept: Understanding adolescent resilience in the context of the Syrian refugee crisis in Bar Elias, Lebanon

Background: The conflict in Syria has led to the displacement of 1.5 million refugees into the neighboring country of Lebanon, with a majority that have yet to return to their homeland. Syrian adolescents in the town of Bar Elias in the Bekaa Valley, Lebanon have lived and grown in the face of resource-limited environments, restricted movement, and a longing for return. Resilience is manifested in the adaptation to such circumstances through close supportive relationships, social engagement, employment, and religion. There is a communal aspect to resilience that is important to the adolescent refugee experience and to the efforts supporting these communities. / Methods: Fifteen one-to-one interviews and two focus groups, with a total of eighteen Syrian adolescents, were analyzed using an inductive thematic analysis informed by grounded theory principles. Participants were recruited through partnering non-governmental organizations (NGOs) in the area, and ethical approval was granted through UCL and the American University in Beirut (AUB). / Results: Syrian adolescents highlighted supportive relationships, communal activities and spaces, memories of home, employment, and shared environments as integral elements to their personal adaptation. Methods of resilience involved social cohesion and establishing stability for one's family and close community. Adaptation to the present is intertwined with facing the consequences of displacement in this new context and maintaining aspirations for a bright future. Engaging with the environments they share and help create is an important facet of resilience and occurs through group gatherings , hobbies, and online communication. Additionally, inner strength can be derived from religious activities and empowers individual processing. / Conclusion: This study illuminates the elements and mechanisms embodied in these adolescents’ communities and relationships that allow for adaptation to life in Bar Elias. These factors strengthen their approach to overcome social barriers and practice resilience. These communal aspects of the adolescents’ lives also connect to their memories of home, current environment, and future aspirations

X-ray Micro-Tomography of Ablative Heat Shield Materials

X-ray micro-tomography is a non-destructive characterization technique that allows imaging of materials structures with voxel sizes in the micrometer range. This level of resolution makes the technique very attractive for imaging porous ablators used in hypersonic entry systems. Besides providing a high fidelity description of the material architecture, micro-tomography enables computations of bulk material properties and simulations of micro-scale phenomena. This presentation provides an overview of a collaborative effort between NASA Ames Research Center and Lawrence Berkeley National Laboratory, aimed at developing micro-tomography experiments and simulations for porous ablative materials. Measurements are carried using x-rays from the Advanced Light Source at Berkeley Lab on different classes of ablative materials used in NASA entry systems. Challenges, strengths and limitations of the technique for imaging materials such as lightweight carbon-phenolic systems and woven textiles are discussed. Computational tools developed to perform numerical simulations based on micro-tomography are described. These enable computations of material properties such as permeability, thermal and radiative conductivity, tortuosity and other parameters that are used in ablator response models. Finally, we present the design of environmental cells that enable imaging materials under simulated operational conditions, such as high temperature, mechanical loads and oxidizing atmospheres.Keywords: Micro-tomography, Porous media, Ablatio

Combined potential and spin impurity scattering in cuprates

We present a theory of combined nonmagnetic and magnetic impurity scattering in anisotropic superconductors accounting for the momentum-dependent impurity potential. Applying the model to the d-wave superconducting state, we obtain a quantitative agreement with the initial suppression of the critical temperature due to Zn and Ni substitutions as well as electron irradiation defects in the cuprates. We suggest, that the unequal pair-breaking effect of Zn and Ni may be related to a different nature of the magnetic moments induced by these impurities.Comment: 5 pages, 3 tables, RevTex, to be published in Phys. Rev.

X-Ray Micro-Tomography Applied to Nasa's Materials Research: Heat Shields, Parachutes and Asteroids

X-ray micro-tomography is used to support the research on materials carried out at NASA Ames Research Center. The technique is applied to a variety of applications, including the ability to characterize heat shield materials for planetary entry, to study the Earth- impacting asteroids, and to improve broadcloths of spacecraft parachutes. From micro-tomography images, relevant morphological and transport properties are determined and validated against experimental data

A New Approach To Light-Weight Ablators Analysis: From Micro-Tomography Measurements to Statistical Analysis and Modeling

The morphology characteristics and ablation behavior of a highly porous carbon fiber preform are studied using a combined experimental/numerical approach. Morphological characterization of the three-dimensional structure of the material is performed by hard X-rays synchrotron micro-tomography at the Advanced Light Source of Lawrence Berkeley National Laboratory. The resulting micro-tomography voxels are used to compute geometrical properties of the carbon preform, like porosity, specific surface area and tortuosity, that are otherwise indirectly measured through experimental techniques. The reconstructed volumes are used to build a computational grid for numerical simulations of the fibers\u27 ablation. By modeling the diffusion of oxygen through the porous medium using Lagrangian methods, and the oxidation at the carbon fibers\u27 surface using a reactivity model, the ablation of the carbon fibers are simulated for a range of Thiele numbers. It is shown that in the diffusion limited regime (large Thiele number), the ablation of the fibers occurs at the surface of the material. In the reaction limited regime (low Thiele number), the oxygen penetrates into the fibers, resulting in volumetric ablation and high material spallation

Full-Scale Mars Science Laboratory Tiled Heatshield Material Response

No abstract availabl

Fertility treatment and cancers—the eternal conundrum: a systematic review and meta-analysis

STUDY QUESTION: Does fertility treatment (FT) significantly increase the incidence of breast, ovarian, endometrial or cervical cancer? SUMMARY ANSWER: Overall, FT does not significantly increase the incidence of breast, ovarian or endometrial cancer and may even reduce the incidence of cervical cancer. WHAT IS KNOWN ALREADY: Infertility affects more than 14% of couples. Infertility and nulliparity are established risk factors for endometrial, ovarian and breast cancer, yet the association with FT is more contentious. STUDY DESIGN, SIZE, DURATION: A literature search was carried out using Cochrane Library, EMBASE, Medline and Google Scholar up to December 2019. Peer-reviewed studies stating cancer incidence (breast, ovarian, endometrial or cervical) in FT and no-FT groups were identified. Out of 128 studies identified, 29 retrospective studies fulfilled the criteria and were included (n = 21 070 337). PARTICIPANTS/MATERIALS, SETTING, METHODS: In the final meta-analysis, 29 studies were included: breast (n = 19), ovarian (n = 19), endometrial (n = 15) and cervical (n = 13), 17 studies involved multiple cancer types and so were included in each individual cancer meta-analysis. Primary outcome of interest was cancer incidence (breast, ovarian, endometrial and cervical) in FT and no-FT groups. Secondary outcome was cancer incidence according to specific fertility drug exposure. Odds ratio (OR) and random effects model were used to demonstrate treatment effect and calculate pooled treatment effect, respectively. A meta-regression and eight sub-group analyses were performed to assess the impact of the following variables, maternal age, infertility, study size, outliers and specific FT sub-types, on cancer incidence. MAIN RESULTS AND THE ROLE OF CHANCE: Cervical cancer incidence was significantly lower in the FT group compared with the no-FT group: OR 0.68 (95% CI 0.46-0.99). The incidences of breast (OR 0.86; 95% CI 0.73-1.01) and endometrial (OR 1.28; 95% CI 0.92-1.79) cancers were not found to be significantly different between the FT and no-FT groups. Whilst overall ovarian cancer incidence was not significantly different between the FT and no-FT groups (OR 1.19; 95% CI 0.98-1.46), separate analysis of borderline ovarian tumours (BOT) revealed a significant association (OR 1.69; 95% CI 1.27-2.25). In further sub-group analyses, ovarian cancer incidence was shown to be significantly higher in the IVF (OR 1.32; 95% CI 1.03-1.69) and clomiphene citrate (CC) treatment group (OR 1.40; 95% CI 1.10-1.77), respectively when compared with the no-FT group. Conversely, the incidences of breast (OR 0.75; 95% CI 0.61-0.92) and cervical cancer (OR 0.58; 95% CI 0.38-0.89) were significantly lower in the IVF treatment sub-group compared to the no-FT group. LIMITATIONS, REASONS FOR CAUTION: The large, varied dataset spanning a wide study period introduced significant clinical heterogeneity. Thus, results have to be interpreted with an element of caution. Exclusion of non-English citations, unpublished work and abstracts, in order to ensure data accuracy and reliability was maintained, may have introduced a degree of selection bias. WIDER IMPLICATIONS OF THE FINDINGS: The results for breast, ovarian, endometrial and cervical cancer are reassuring, in line with previously published meta-analyses for individual cancers but the association between IVF and CC treatment and an increase in ovarian cancer incidence requires additional work to understand the potential mechanism driving this association. In particular, focusing on (i) discriminating specific treatments effects from an inherent risk of malignancy; (ii) differential risk profiles among specific patient sub-groups (refractory treatment and obesity); and (iii) understanding the impact of FT outcomes on cancer incidence. STUDY FUNDING/COMPETING INTEREST(S): This study did not receive any funding. The authors have no financial, personal, intellectual and professional conflicts of interest to declare. PROSPERO REGISTRATION NUMBER: CRD42019153404

Effect of anisotropic impurity scattering in superconductors

We discuss the weak-coupling BCS theory of a superconductor with the impurities, accounting for their anisotropic momentum-dependent potential. The impurity scattering process is considered in the t-matrix approximation and its influence on the superconducting critical temperature is studied in the Born and unitary limit for a d- and (d+s)-wave superconductors. We observe a significant dependence of the pair-breaking strength on the symmetry of the scattering potential and classify the impurity potentials according to their ability to alter T_c. A good agreement with the experimental data for Zn doping and oxygen irradiation in the overdoped cuprates is found.Comment: 31 pages, RevTex, 15 PostScript figure