267 research outputs found

    Tris(hydroxypropyl)phosphine Oxide: A Chiral Three-Dimensional Material with Nonlinear Optical Properties

    Get PDF
    The achiral C_(3v) organic phosphine tris(hydroxypropyl)phosphine oxide (1) crystallizes in the unusual chiral hexagonal space group P6_3. The structure is highly ordered because each phosphine oxide moiety forms three hydrogen bonds with adjacent hydroxy groups from three different molecules. The properties of the crystals and the presence of hydrogen bonding interactions were investigated using single crystal Raman spectroscopy. The crystals show nonlinear optical properties and are capable of efficient second harmonic generation

    Benzyl 2-methyl-3-[( E

    Get PDF

    Tourism income and economic growth in Greece: Empirical evidence from their cyclical components

    Get PDF
    This paper examines the relationship between the cyclical components of Greek GDP and international tourism income for Greece for the period 1976–2004. Using spectral analysis the authors find that cyclical fluctuations of GDP have a length of about nine years and that international tourism income has a cycle of about seven years. The volatility of tourism income is more than eight times the volatility of the Greek GDP cycle. VAR analysis shows that the cyclical component of tourism income is significantly influencing the cyclical component of GDP in Greece. The findings support the tourism-led economic growth hypothesis and are of particular interest and importance to policy makers, financial analysts and investors dealing with the Greek tourism industry

    Increased Nonconducted P-Wave Arrhythmias after a Single Oil Fly Ash Inhalation Exposure in Hypertensive Rats

    Get PDF
    Background: Exposure to combustion-derived fine particulate matter (PM) is associated with increased cardiovascular morbidity and mortality especially in individuals with cardiovascular disease, including hypertension. PM inhalation causes several adverse changes in cardiac function that are reflected in the electrocardiogram (ECG), including altered cardiac rhythm, myocardial ischemia, and reduced heart rate variability (HRV). The sensitivity and reliability of ECG-derived parameters as indicators of the cardiovascular toxicity of PM in rats are unclear. Objective: We hypothesized that spontaneously hypertensive (SH) rats are more susceptible to the development of PM-induced arrhythmia, altered ECG morphology, and reduced HRV than are Wistar Kyoto (WKY) rats, a related strain with normal blood pressure. Methods: We exposed rats once by nose-only inhalation for 4 hr to residual oil fly ash (ROFA), an emission source particle rich in transition metals, or to air and then sacrificed them 1 or 48 hr later. Results: ROFA-exposed SH rats developed nonconducted P-wave arrhythmias but no changes in ECG morphology or HRV. We found no ECG effects in ROFA-exposed WKY rats. ROFA-exposed SH rats also had greater pulmonary injury, neutrophil infiltration, and serum C-reactive protein than did ROFA-exposed WKY rats. Conclusions: These results suggest that cardiac arrhythmias may be an early sensitive indicator of the propensity for PM inhalation to modify cardiovascular function. Originally published Environmental Health Perspectives, Vol. 117, No. 5, May 200

    Female senior secondary physics students’ engagement in science: a qualitative study of constructive influences

    Get PDF
    Background: Prompted by fewer females compared to males enrolling in physics and advanced mathematics at both secondary and university levels, our research investigated the views and experiences of female students currently studying upper secondary school physics. We interviewed 18 female students about influences they considered important to their own science education, interest in science, and future science-related aspirations. Our purpose was to identify the experiences that these students most strongly associated with the generation and maintenance of their engagement in science, particularly represented in this research by their enrolment in upper secondary physics. Results: The research team used a systematic, iterative process to identify the main themes in the transcribed interview data. We identified the influence each girl reported as the strongest (ranked first). We also combined all influences that the participants had nominated, regardless of their ranking, to further examine all factors participants suggested as influential in their sustained engagement in school science (represented by their decision to study upper secondary physics). Systematic analysis of the interview data confirms that the influences on these females’ choices to study physics at upper secondary originate from a combination of their teachers, their school’s science culture, members of their family, the participants themselves and their peers. Conclusions: The interviews highlighted the idiographic complexities in understanding the wide range of important influences on these students studying physics at upper secondary school and their engagement in science. The unique contribution of this work is giving voice to the participants and reflecting on what these high achieving females have to say about the influential factors in their decisions to pursue science. Supportive teachers and the school science culture play essential roles, and other cultural and/or social factors such as family members and peers are identified as important. References to the culture and expectations of the school, family holidays, and conversations with siblings are support factors that seem to interact and overlap. At the same time, the importance of policy-amenable factors such as competent and caring science teachers, and science-supportive school cultures should be emphasised and encouraged
    • 

    corecore