A Novel Bis(phosphido)pyridine [PNP]^(2−) Pincer Ligand and Its Potassium and Bis(dimethylamido)zirconium(IV) Complexes

A novel PNP bis(secondary phosphine)pyridine pincer ligand, 2,6-bis(2-(phenylphosphino)phenyl)pyridine, has been prepared in high yield, and the properties of the doubly deprotonated form as a ligand in K_4(PNP)_2(THF)_6 and (PNP)Zr(NMe_2)_2 have been investigated. The neutral PNP ligand has been isolated as a mixture of noninterconverting diastereomers, due to the presence of two chirogenic phosphorus atoms of the secondary phopshines, but coordination of the dianionic form to potassium and zirconium allows for isolation of a single diastereomer in near-quantitative yield. The structure of a bis(dimethylamido)zirconium(IV) derivative of the bis(phosphido)pyridine ligand and DFT calculations suggest that the phosphides do not π-bond to early transition metals, likely due to geometric strain and possibly orbital size mismatch between phosphorus and zirconium. As a result, the soft phosphides are prone to formation of insoluble oligomers with substantial bridging of the phosphido lone pairs to other zirconium centers

The Refugee Problem: An International Legal Tangle

Change is constant and computing paradigm is no exception. It has witnessed major shifts right from centralized client server systems to widely distributed systems. This time the locus of change in the computing paradigm is moving towards virtualization, paving way to cloud computing. Cloud computing aims at providing computing services to its users as an utility. It allows its authenticated users to access a wide range of highly scalable computing capabilities and services via the internet on a pay-per-usage basis. Organisations not only view these benefits as cost-saving strategies, but also aim at improving the competitive advantages using cloud computing. Hence, this has given rise to a new horizon in IT/IS outsourcing. With a collaboration of cloud computing and outsourcing emerged a new concept called cloudsourcing. Cloudsourcing can be termed as the next generation outsourcing and the next phase of cloud computing promising benefits from both the areas. Cloudsourcing is outsourcing traditional business via the cloud infrastructure. Though there is pompous popularity surrounding this new technology, there is much hesitation in adopting it due to the inherent security issues. This paper discusses in detail the security issues and possible solution to the same. As this is a new concept, not much work is identified to be done in providing a set of guidelines to adopt cloudsourcing that are very specific to information security. This work intends to fill this aperture by building a set of well-defined information security guidelines, which can be termed as a novel. For this purpose, design science research method proposed by Hevner et al is used so as to accomplish this goal. Initially, a literature study is done after which an exploratory study comprising of interviews is done to gather qualitative data. The results of the exploratory interview is tested for correctness and evaluated based on an evaluation study comprising a survey based questionnaire. The analysis of the evaluation study results provides the final results. In such an attempt, the identified countermeasures to risks are classified into three groups namely, organisational, technical and regulatory and compliance guidelines. Hence the end results constituting the set of information security guidelines are classified into the above mentioned groups. This work is assumed to contribute to our understanding of information security in cloudsourcing and in supporting IT decision makers, IT project managers and security executives of organisations for a smooth and secure transition towards cloudsourcing their business

Rana chiricahuensis

Number of Pages: 2Integrative BiologyGeological Science

Spitzer spectroscopy of circumstellar disks in the 5 Myr old upper Scorpius OB association

We present mid-infrared spectra between 5.2 and 38 μm for 26 disk-bearing members of the ~5 Myr old Upper Scorpius OB association obtained with the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope. We find clear evidence for changes in the spectral characteristics of dust emission between the early-type (B+A) and late-type (K+M) infrared excess stars. The early-type members exhibit featureless continuum excesses that become apparent redward of ~8 μm. In contrast, 10 and 20 μm silicate features or polycyclic aromatic hydrocarbon emission are present in all but one of the late-type excess members of Upper Scorpius. The strength of silicate emission among late-type Upper Scorpius members is spectral-type dependent, with the most prominent features being associated with K5-M2-type stars. By fitting the spectral energy distributions (SED) of a representative sample of low-mass stars with accretion disk models, we find that the SEDs are consistent with models having inner disk radii ranging from ~0.2 to 1.2 AU. Complementary high-resolution (R ~ 33,000) optical (λλ4800-9200) spectra for the Upper Scorpius excess stars were examined for signatures of gaseous accretion. Of the 35 infrared excess stars identified in Upper Scorpius, only seven (all late-type) exhibit definitive signatures of accretion. Mass-accretion rates (M) for these stars were estimated to range from 10^–11 to 10^–8.9 M⊙ yr^–1. Compared to Class II sources in Taurus-Auriga, the disk population in Upper Scorpius exhibits reduced levels of near- and mid-infrared excess emission and an order of magnitude lower mass-accretion rates. These results suggest that the disk structure has changed significantly over the 2-4 Myr in age separating these two stellar populations. The ubiquity of depleted inner disks in the Upper Scorpius excess sample implies that such disks are a common evolutionary pathway that persists for some time

Turing pattern outside of the Turing domain

There are two simple solutions to reaction-diffusion systems with limit-cycle reaction kinetics, producing oscillatory behaviour. The reaction parameter $\mu$ gives rise to a ‘space-invariant’ solution, and $\mu$ versus the ratio of the diffusion coefficients gives rise to a ‘time-invariant’ solution. We consider the case where both solution types may be possible. This leads to a refinement of the Turing model of pattern formation. We add convection to the system and investigate its effect. More complex solutions arise that appear to combine the two simple solutions. The convective system sheds light on the underlying behaviour of the diffusive system

Limit cycles in the presence of convection, a first order analysis

We consider a diffusion model with limit cycle reaction functions. In an unbounded domain, diffusion spreads pattern outwards from the source. Convection adds instability to the reaction-diffusion system. We see the result of the instability in a readiness to create pattern. In the case of strong convection, we consider that the first-order approximation may be valid for some aspects of the solution behaviour. We employ the method of Riemann invariants and rescaling to transform the reduced system into one invariant under parameter change. We carry out numerical experiments to test our analysis. We find that most aspects of the solution do not comply with this, but we find one significant characteristic which is approximately first order. We consider the correspondence of the Partial Differential Equation with the Ordinary Differential Equation along rays from the initiation point in the transformed system. This yields an understanding of the behaviour