title: Synthesis and crystal structure of the first complex containing a chelating selenourea dianion ligand

authors: Nicholson, Brian K.

subjects: Platinum complexes

abstract: Reaction of N,N′-diphenylselenourea, PhNHC(Se)NHPh, with cis-[PtCl2(PPh3)2] and triethylamine in hot methanol gives the first example of a selenourea dianion complex, [Pt{SeC(=NPh)NPh}(PPh3)2] isolated as a yellow solid in high yield. The structure of the complex was determined by X-ray crystallography and found to be similar to the related thiourea dianion complex [Pt{SC(=NPh)NPh}(PPh3)2], with a Pt---Se---C---N four-membered ring. The antitumour activity (P388 murine leukaemia cells) of the selenourea dianion complex was determined, together with a small selection of related platinum(II)-thiourea dianion complexes (prepared by an analogous method) for comparison. The complex [Pt{SC(=NMe)NMe}(PPh3)2] showed high activity [IC50 1.0 μM], with the other complexes showing moderate to low activity.

text: Synthesis and crystal structure of the first complex containing a chelating selenourea dianion ligand Reaction of N,N′-diphenylselenourea, PhNHC(Se)NHPh, with cis-[PtCl2(PPh3)2] and triethylamine in hot methanol gives the first example of a selenourea dianion complex, [Pt{SeC(=NPh)NPh}(PPh3)2] isolated as a yellow solid in high yield. The structure of the complex was determined by X-ray crystallography and found to be similar to the related thiourea dianion complex [Pt{SC(=NPh)NPh}(PPh3)2], with a Pt---Se---C---N four-membered ring. The antitumour activity (P388 murine leukaemia cells) of the selenourea dianion complex was determined, together with a small selection of related platinum(II)-thiourea dianion complexes (prepared by an analogous method) for comparison. The complex [Pt{SC(=NMe)NMe}(PPh3)2] showed high activity [IC50 1.0 μM], with the other complexes showing moderate to low activity.

year: 2003-11-01

title: Development of a New Event-Based Rainfall-Runoff Equation Based on Average Rainfall Intensity During an Event

authors: Shokri, Ali

abstract: Event-based rainfall-runoff models are practical tools commonly used to predict catchments’ response to a rainfall event. However, one of the main concerns is that the characteristics of rain events are neglected in the model development. This paper develops a novel event-based rainfall-runoff equation to incorporate rainfall characteristics into account. The performance of the new equation is evaluated based on the root mean square error, Nash–Sutcliffe efficiency coefficient, and per cent bias for 13,339 rainfall-runoff events between 2005 and 2020 over 23 catchments across New Zealand and Australia with oceanic, mediterranean, tropical, subtropical, and semiarid climates. Compared to the previous event-based models, the new equation shows an improvement in runoff estimation in almost all case studies. Furthermore, considering the new equation is simple, efficient, and takes the rain event duration into account, the new equation has the potential to become a robust alternative method to the conventional curve number method in hydrological engineering projects.

text: Development of a New Event-Based Rainfall-Runoff Equation Based on Average Rainfall Intensity During an Event Event-based rainfall-runoff models are practical tools commonly used to predict catchments’ response to a rainfall event. However, one of the main concerns is that the characteristics of rain events are neglected in the model development. This paper develops a novel event-based rainfall-runoff equation to incorporate rainfall characteristics into account. The performance of the new equation is evaluated based on the root mean square error, Nash–Sutcliffe efficiency coefficient, and per cent bias for 13,339 rainfall-runoff events between 2005 and 2020 over 23 catchments across New Zealand and Australia with oceanic, mediterranean, tropical, subtropical, and semiarid climates. Compared to the previous event-based models, the new equation shows an improvement in runoff estimation in almost all case studies. Furthermore, considering the new equation is simple, efficient, and takes the rain event duration into account, the new equation has the potential to become a robust alternative method to the conventional curve number method in hydrological engineering projects.

year: 2023

title: Role of tephra in dating Polynesian settlement and impact, New Zealand

authors: Lowe, David J.

subjects: tephrochronology

abstract: Tephrochronology in its original sense is the use of tephra layers as time-stratigraphic marker beds to establish numerical or relative ages (Lowe and Hunt, 2001). Tephra layers have been described and studied in New Zealand for more than 160 years (the German naturalist and surgeon Ernst Dieffenbach described ‘recognizable’ tephra sections in his 1843 book Travels in New Zealand), and the first isopach map, showing fallout from the deadly plinian basaltic eruption of Mt Tarawera on 10 June 1886, was published in 1888 (Lowe, 1990; Lowe et al., 2002). More recently, a wide range of tephra-related paleoenvironmental research has been undertaken (e.g., Lowe and Newnham, 1999; Newnham and Lowe, 1999; Newnham et al., 1999, 2004; Shane, 2000), including new advances in the role of tephra in linking and dating sites containing evidence for abrupt climatic change (e.g., Newnham and Lowe, 2000; Newnham et al., 2003). Here we focus on the use of tephrochronology in dating the arrival and impacts of the first humans in New Zealand, a difficult problem for which this technique has proven to be of critical importance.

text: Role of tephra in dating Polynesian settlement and impact, New Zealand Tephrochronology in its original sense is the use of tephra layers as time-stratigraphic marker beds to establish numerical or relative ages (Lowe and Hunt, 2001). Tephra layers have been described and studied in New Zealand for more than 160 years (the German naturalist and surgeon Ernst Dieffenbach described ‘recognizable’ tephra sections in his 1843 book Travels in New Zealand), and the first isopach map, showing fallout from the deadly plinian basaltic eruption of Mt Tarawera on 10 June 1886, was published in 1888 (Lowe, 1990; Lowe et al., 2002). More recently, a wide range of tephra-related paleoenvironmental research has been undertaken (e.g., Lowe and Newnham, 1999; Newnham and Lowe, 1999; Newnham et al., 1999, 2004; Shane, 2000), including new advances in the role of tephra in linking and dating sites containing evidence for abrupt climatic change (e.g., Newnham and Lowe, 2000; Newnham et al., 2003). Here we focus on the use of tephrochronology in dating the arrival and impacts of the first humans in New Zealand, a difficult problem for which this technique has proven to be of critical importance.

year: 2004