Photoassociation spectra and the validity of the dipole approximation for weakly bound dimers

Photoassociation (PA) of ultracold metastable helium to the 2s2p manifold is theoretically investigated using a non-perturbative close-coupled treatment in which the laser coupling is evaluated without assuming the dipole approximation. The results are compared with our previous study [Cocks and Whittingham, Phys. Rev. A 80, 023417 (2009)] that makes use of the dipole approximation. The approximation is found to strongly affect the PA spectra because the photoassociated levels are weakly bound, and a similar impact is predicted to occur in other systems of a weakly bound nature. The inclusion or not of the approximation does not affect the resonance positions or widths, however significant differences are observed in the background of the spectra and the maximum laser intensity at which resonances are discernable. Couplings not satisfying the dipole selection rule |J-1| <= J' <= |J+1| do not lead to observable resonances.Comment: 5 pages, 2 figures; Minor textual revision

Public Facilitation of Small Farmer Access to International Food Marketing Channels: An Empirical Analysis of the USDA Market Assistance Program in Armenia

With the continued globalization, rapid channel consolidation, increasing technology, capital, food safety and private grades and standards requirements, many small scale agricultural and horticultural producers from transitional and developing countries are rapidly becoming excluded from international agri-food marketing system. Consequently, governments and international agencies alike are reevaluating the structure, form, and delivery of their assistance programs as they search to identify new delivery mechanisms that can overcome the weaknesses that their traditional programs face within this new business environment. Their challenge is to design programs that facilitate the establishment of economically viable and sustainable market relationships and business models between small-scale producers and the international food marketing system that provide these financially distress producers access to the technological know-how, market knowledge and access, and financial and productive resources required to successively compete. Recent Central and Eastern European (CEE) experiences indicate that foreign direct investment and the entry of multinational firms have successfully facilitated small farmers access to international marketing channels. By entering markets with sufficient capital to ensure contract enforcement and support investment, multinational firms can overcome the pervasive hold-up and underinvestment problems plaguing the sector thereby stimulating investment and growth in agricultural production (Gow & Swinnen, 1998; 2001; Walkenhorst, 2000; Dries & Swinnen, 2004). For numerous reasons access to sufficient foreign direct investment or multinational firms may not be an option for many countries. The obvious question therefore becomes, can an alternative third-party facilitation mechanism for stimulating agriculture be identified apart from the private solutions found in Central and East Europe? Glover and Kusterer (1990), Porter and Philips-Howard (1997), Coulter et al (1999), Eaton and Shepherd (2001), and Simmons (2001) allude to the benefits of public agencies in facilitating firm farmer relationships. However as of now the literature has not identified nor extracted the critical processes and factors required in the design, development and establishment of long-run economically viable and sustainable business models that facilitate small producers' access to international food markets. In this research we develop a theoretical model explaining the critical processes and factors involved in the public facilitation of the establishment of economically sustainable marketing relationships between small producers and agroprocessors in the presence of financial distress and absence of effective enforcement mechanisms. The USDA Market Assistance Program (MAP) in Armenia is used to empirically test the theoretical model as it provides a natural experiment. Aremina's recovery is similar to those observed in other CEE countries; however Armenia's agricultural sector has not experienced the recovery found elsewhere. A key constraining factor has been the lack of foreign direct investment initiated solutions so successfully employed elsewhere (World Bank, 1999; 2002). Without the presence of private solutions that can create self-enforcing relationships and encourage relationship specific investment, the Armenian agricultural sector has remained in a sub optimal equilibrium characterized by deep financial distress and a general lack of investment. The only sub-sectors that have seen growth any growth have had MAP facilitation support. Thus what is unique is that the MAP project appears to provide a public solution rather than a private solution to the problem, as in all the previous research (Gow & Swinnen, 1998; 2001; Foster, 1999; Gow et al, 2000; Walkenhorst, 2000; Dries & Swinnen, 2004; Cocks & Gow, 2003). In order to examine the phenomena of establishment and development of sustainable inter-organizational marketing relationships within the context of Armenian agriculture, the USDA MAP project, and the goat industry, we have used mixed methodological approach combining qualitative and quantitative data collection. Approximately 100 semi-structured interviews were conducted with farmers, industry representatives, local experts, and USDA MAP personnel. In additional, an extensive enumerated survey was implemented questioning 2000 farmers in five sectors over 2003 and 2004. Based upon the extensive interviews 12 different business models and facilitation processes used by the USDA MAP were identified and a suitable stratified survey frame was designed to test the differences between these models. The theoretical model and empirical results indicate that the third party public facilitator, USDA MAP, is critical in facilitating the initial development of the channel and identifying a value proposition in a downstream market. However, economic sustainability requires that the public agency remain an arms-length third party facilitator, rather than being the leader in the development of the channel and thus an integral cog in the channel. The actual development of the marketing channel should be led by an entrepreneur who possesses both the ability to develop the marketing channel and who is trusted by the local community. By leading the development of the channel the private enforcement capital that is created through the development of the channel is created between the entrepreneur and the farmers. Over time this widens the self enforcing range of the relationship, therefore allowing greater shifts in market conditions and decreasing the risk of opportunistic behavior (Gow et al, 2000). By holding the trust and respect of the community the entrepreneur inherently holds private enforcement capital with the rest of the community equivalent to the present value of their reputation or trust individually and collectively with the community (Oliver & Gow, 2002). Additionally, the expectation of a value proposition of a downstream market creates the expectation of private enforcement capital between farmers the entrepreneur through the present value of future returns that the entrepreneur could earn from the value proposition (Gow et al, 2000). Thus the combination of the present value of the entrepreneur's reputation with the farmers in the short term combined with the longer term expectation of future returns through the value proposition and creates sufficient private enforcement capital for the immediate development of a self-enforcing relationship with the farmers.International Relations/Trade,

Thick film silicon growth techniques

Thick film silicon ribbons were produced by means of the edge-defined, film-fed growth (EFG) technique. EFG is a process by which single crystals may be grown having a shape controlled by the outside dimensions of a die, the growth taking place from an extremely thin film of liquid fed by capillary action from a crucible below. The principal problem to be overcome in the application of this process to the growth of thick film silicon ribbon relates to the material, such as the shaping die. For the method to operate, this die material must be wet by the liquid silicon. To preserve semiconductor quality, the liquid silicon must not react significantly with the die material. The most promising die material for this application appears to be SiC and SiC-SiO2 admixture. In this case good wetting occurs between the molten silicon and the SiC. C is a relatively unharmful contaminant of Si and additions of quartz to SiC are found to decrease the extent of reaction

Thick film silicon growth techniques

Silicon ribbon growth experiments were conducted using orifices (dies) fabricated from SiC-SiO2 mixtures, fused quartz, SiC, and fine-grained, high density graphite. The best results were obtained from graphite dies. A number of different approaches was tried in modifying the thermal gradient in the dies and in holding the dies. The best results here were obtained from a 0.25-in. thick Mo disc holding a graphite die directly and fitting the die quite closely. Ribbon growths as wide as 9 mm were obtained, while the longest ribbon was 450 x 3.5 x 0.5 mm. Resistivities of ribbons grown from graphite dies have been measured over the range of 0.03 to 1.6 ohm-cm. Some thoughts and literature findings are presented regarding refractory oxide materials as potential orifices

Simultaneous description of four positive and four negative parity bands

The extended coherent state model is further extended in order to describe two dipole bands of different parities. The formalism provides a consistent description of eight rotational bands. A unified description for spherical, transitional and deformed nuclei is possible. Projecting out the angular momentum and parity from a sole state, the $K^{\pi}=1^+$ band acquires a magnetic character, while the electric properties prevail for the other band. Signatures for a static octupole deformation in some states of the dipole bands are pointed out. Some properties which distinguish between the dipole band states and states of the same parity but belonging to other bands are mentioned. Interesting features concerning the decay properties of the two bands are found. Numerical applications are made for $^{158}$Gd, $^{172}$Yb, $^{228,232}$Th, $^{226}$Ra, $^{238}$U and $^{238}$Pu, and the results are compared with the available data.Comment: 36 pages, 13 figures, 12 table

How my clinical placement in Australia helped me to become the clinician I am today

In the global society in which we live the graduate speech-language pathologist needs to be prepared for working with a culturally diverse client group and for the possibility that they may work in a country other than the one in which they trained. International clinical placement opportunities are a common method for many Australian speech language pathology programs to prepare students for an international career and for working with a culturally diverse client group. There have been many reported benefits for students taking part in these placements. But what are the benefits for overseas students who participate in a placement in Australia? This clinical insights article asked five clinicians who had trained in the UK and who had completed a placement in Australia during their training to reflect on this experience. They reported many benefits both personally and professionally. They felt that their Australian placement experience prepared them to work with a culturally diverse client group and shaped who they areas clinicians. There were also additional benefits for the service in which they now worked

Professional killers: The role of extracellular vesicles in the reciprocal interactions between natural killer, CD8+ cytotoxic T-cells and tumour cells

Extracellular vesicles (EVs) mediate the cross-talk between cancer cells and the cells of the surrounding Tumour Microenvironment (TME). Professional killer cells include Natural Killer (NK) cells and CD8+ Cytotoxic T-lymphocytes (CTLs), which represent some of the most effective immune defense mechanisms against cancer cells. Recent evidence supports the role of EVs released by NK cells and CTLs in killing cancer cells, paving the road to a possible therapeutic role for such EVs. This review article provides the state-of-the-art knowledge on the role of NK- and CTL-derived EVs as anticancer agents, focusing on the different functions of different sub-types of EVs. We also reviewed the current knowledge on the effects of cancer-derived EVs on NK cells and CTLs, identifying areas for future investigation in the emerging new field of EV-mediated immunotherapy of cancer

Laser Intensity Dependence of Photoassociation in Ultracold Metastable Helium

Photoassociation of spin-polarized metastable helium to the three lowest rovibrational levels of the J=1, $0_u^+$ state asymptoting to 2$s {}^{3}$S$_{1}+2p {}^{3}$P$_{0}$ is studied using a second-order perturbative treatment of the line shifts valid for low laser intensities, and two variants of a non-perturbative close-coupled treatment, one based upon dressed states of the matter plus laser system, and the other on a modified radiative coupling which vanishes asymptotically, thus simulating experimental conditions. These non-perturbative treatments are valid for arbitrary laser intensities and yield the complete photoassociation resonance profile. Both variants give nearly identical results for the line shifts and widths of the resonances and show that their dependence upon laser intensity is very close to linear and quadratic respectively for the two lowest levels. The resonance profiles are superimposed upon a significant background loss, a feature for this metastable helium system not present in studies of photoassociation in other systems, which is due to the very shallow nature of the excited state $0_u^+$ potential. The results for the line shifts from the close-coupled and perturbative calculations agree very closely at low laser intensities.Comment: 14 pages, 7 figures, title altered, text reduce