Temperature optimization of optical-phase conjugation in dye doped polymer-films

Experimental results of the temperature dependence of the nonlinear optical response of methyl red doped polymethylmethacrylate films in the range 20°C to 170°C are reported. It is found that the intensity of the phase conjugate signal resulting from degenerate four-wave mixing using pump and probe beams with parallel polarisation states increases dramatically on heating by a factor of ∼ 10, reaching a maximum at ∼ 100°C. The intensity of the phase conjugate signal for the case with crossed polarisation states of the pump and probe beams drops monotonically with increasing temperature. For both configurations the response time shortens with increasing temperature. The particular role of the polymer matrix in this temperature variation of the nonlinear optical response is discussed.

Temperature-tuned vector phase conjugation in azobenzene dye impregnated polymer films

Near-perfect vector phase conjugation was achieved at 488 nm in a methyl red dye impregnated polymethylmethacrylate film by employing a temperature tuning technique. Using a degenerate four-wave mixing geometry with vertically polarized counterpropagating pump beams, intensity and polarization gratings were written in the dye/polymer system using a vertically or horizontally polarized weak probe beam. Over a limited temperature range, as the sample was heated, the probe reflectivity from the polarization grating dropped but the reflectivity from the intensity grating rose sharply. At a sample temperature of approximately 50°C, the reflectivities of the gratings were measured to be equal and we confirmed that, at this temperature, the measured vector phase conjugate fidelity was very close to unity. We discuss a possible explanation of this effect.

Nano structures through self-assembly of protected hydrophobic amino acids: encapsulation of rhodamine B dye by proline-based nanovesicles

The development of novel molecules for the creation of nanometer structures with specific properties has been the current interest of this research. We have developed a set of molecules from hydrophobic omega- and alpha-amino acids by protecting the -NH(2) with Boc (t-butyloxycarbonyl) group and -CO(2)H with para-nitroanilide such as BocHN-Xx-CONH-(p-NO(2))center dot C(6)H(4), where Xx is gamma-aminobutyric acid (gamma-Abu), (L)-isoleucine, alpha-aminoisobutyric acid, proline, etc. These molecules generate various nanometer structures, such as nanofibrils, nanotubes and nanovesicles, in methanol/water through the self-assembly of bilayers in which the nitro benzene moieties are stacked in the middle and the Boc-protected amino acids parts are packed in the outer surface. The bilayers can be further stacked one over the other through hydrophobic interactions to form multilayer structure, which helps to generate different kinds of nanoscopic structures. The formation of the nanostructures has been facilitated through the participation of various noncovalent interactions, such as hydrophobic interactions, hydrogen bonding and aromatic p-stacking interactions. Fluorescence microscopy and UV studies reveal that the nanovesicles generated from pro-based molecule can encapsulate dye molecules which can be released by addition of acid (at pH 2). These single amino acid based molecules are both easy to synthesize and cost-effective and therefore offer novel scaffolds for the future design of nanoscale structures.

Competing for attentional priority: temporary goals versus threats

Numerous studies have shown that attention is biased toward threatening events. More recent evidence has also found attentional biases for stimuli that are relevant to the current and temporary goals of an individual. We examined whether goal-relevant information still evokes an attentional bias when this information competes with threatening events. In three experiments, participants performed a dot probe task combined with a separate task that induced a temporary goal. The results of Experiment 1 showed that attention was oriented to goal-relevant pictures in the dot probe task when these pictures were simultaneously presented with neutral or threatening pictures. Whether goal-relevant pictures themselves were threatening or neutral did not influence the results. Experiment 2 replicated these findings in a sample of highly trait-anxious participants. Experiment 3 showed that attention was automatically deployed to stimuli relevant to a temporary goal even in the presence of stimuli that signal imminent and genuine threat (i.e., a colored patch signaling the presentation of an aversive noise). These findings further corroborate the conclusion that an individual's current and temporary goals guide early attentional processes

The politics of temporary work deregulation in Europe: solving the French puzzle

Temporary work has expanded in the last three decades with adverse implications for inequalities. Because temporary workers are a constituency that is unlikely to impose political costs, governments often choose to reduce temporary work regulations. While most European countries have indeed implemented such reforms, France went in the opposite direction, despite having both rigid labour markets and high unemployment. My argument to solve this puzzle is that where replaceability is high, workers in permanent and temporary contracts have overlapping interests, and governments choose to regulate temporary work to protect permanent workers. In turn, replaceability is higher where permanent workers’ skills are general and wage coordination is low. Logistic regression analysis of the determinants of replaceability — and how this affects governments’ reforms of temporary work regulations — supports my argument. Process tracing of French reforms also confirm that the left has tightened temporary work regulations to compensate for the high replaceability.

Essays on labour market dualisation in Western Europe: active labour market policies, temporary work regulation and inequality

European labour markets are increasingly divided between insiders in full-time permanent employment and outsiders in precarious work or unemployment. Using quantitative as well as qualitative methods, this thesis investigates the determinants and consequences of labour market policies that target these outsiders in three separate papers. The first paper looks at Active Labour Market Policies (ALMPs) that target the unemployed. It shows that left and right-wing parties choose different types of ALMPs depending on the policy and the welfare regime in which the party is located. These findings reconcile the conflicting theoretical expectations from the Power Resource approach and the insider-outsider theory. The second paper considers the regulation and protection of the temporary work sector. It solves the puzzle of temporary re-regulation in France, which contrasts with most other European countries that have deregulated temporary work. Permanent workers are adversely affected by the expansion of temporary work in France because of general skills and low wage coordination. The interests of temporary and permanent workers for re-regulation therefore overlap in France and left governments have an incentive to re-regulate the sector. The third paper then investigates what determines inequality between median and bottom income workers. It shows that non-inclusive economic coordination increases inequality in the absence of compensating institutions such as minimum wage regulation. The deregulation of temporary work as well as spending on employment incentives and rehabilitation also has adverse effects on inequality. Thus, policies that target outsiders have important economic effects on the rest of the workforce. Three broader contributions can be identified. First, welfare state policies may not always be in the interests of labour, so left parties may not always promote them. Second, the interests of insiders and outsiders are not necessarily at odds. Third, economic coordination may not be conducive to egalitarianism where it is not inclusive.

Investigating hydrological regimes and processes in a set of catchments with temporary waters in Mediterranean Europe

Seven catchments of diverse size in Mediterranean Europe were investigated in order to understand the main aspects of their hydrological functioning. The methods included the analysis of daily and monthly precipitation, monthly potential evapotranspiration rates, flow duration curves, rainfall runoff relationships and catchment internal data for the smaller and more instrumented catchments. The results showed that the catchments were less dry than initially considered. Only one of them was really semi-arid throughout the year. All the remaining catchments showed wet seasons when precipitation exceeded potential evapotrans-piration, allowing aquifer recharge, wet runoff generation mechanisms and relevant baseflow contribution. Nevertheless, local infiltration excess (Hortonian) overland flow was inferred during summer storms in some catchments and urban overland flow in some others. The roles of karstic groundwater, human disturbance and low winter temperatures were identified as having an important impact on the hydrological regime in some of the catchments.

Union inclusiveness and temporary agency workers: the role of power resources and union ideology

This article investigates the determinants of union inclusiveness towards agency workers in Western Europe, using an index which combines unionization rates with dimensions of collective agreements covering agency workers. Using fuzzy-set Qualitative Comparative Analysis, we identify two combinations of conditions leading to inclusiveness: the ‘Northern path’ includes high union density, high bargaining coverage and high union authority, and is consistent with the power resources approach. The ‘Southern path’ combines high union authority, high bargaining coverage, statutory regulations of agency work and working-class orientation, showing that ideology rather than institutional incentives shapes union strategies towards the marginal workforce.

Nontraditional employment: the careers of temporary workers

This chapter focuses upon the careers of temporary workers. Temporary employment for many workers presents a route to permanent employment. Other workers, however, get trapped into temporary employment or cycle between unstable jobs and spells of unemployment. Predictors of such transitions are multiple. We selected two broad categories, namely perceived employability from the area of career research and health and well-being from the area of occupational health and well-being research. The overall conclusion is that the association between temporary employment and both perceived employability and health and well-being is inconclusive. This suggests that there are boundary conditions that may make some temporary workers successful and others not. Risk factors include dynamics related to the dual labor market, including lower job quality, lower investments on the part of employers, and negative stereotyping of temporary workers as second-class citizens. On the positive side, many temporary workers have learned to manage their careers in the sense that they invest in training and in continuous job search.

Developing temporary manufacturing facilities for residential building: a case of the modern flying factory

The building industry is often berated for its short comings in meeting up with the demand for the provision of new housing. Addressing the need for new housing stock is a challenge that has led to debates among professional bodies, the construction sector, housing industry and government. The introduction of new manufacturing technologies is often offered as a solution, but the challenges of increasing the amount of off-site construction in residential building are well known and well-rehearsed. The modern flying factory (MFF) is a concept that involves the manufacture of specific components or modules in temporary off- or near- site locations using relatively simple and quick to set up and dismantle technologies and processes. The aim is to produce short batches and hence achieve some of the benefits of off-site manufacture on a much smaller scale than in dedicated factory environments. A case study of a modern flying factory being set up to produce pre-assembled utility cupboards for a large residential development in London is presented, involving participant observation and informal interviews with key actors on the design and operationalising of the process. The case reveals that although there are costs, efficiency and health and safety benefits to using MFF approaches, there are also challenges to overcome over the time required to set up and establish the process for relatively short runs, and in evaluating whether the MFF or traditional site based production is most effective for particular aspects of projects.

Quantitative structure of an acetate dye molecule analogue at the TiO2- acetic acid interface

The positions of atoms in and around acetate molecules at the rutile TiO2(110) interface with 0.1 M acetic acid have been determined with a precision of ±0.05 Å. Acetate is used as a surrogate for the carboxylate groups typically employed to anchor monocarboxylate dye molecules to TiO2 in dye-sensitised solar cells (DSSC). Structural analysis reveals small domains of ordered (2 x 1) acetate molecules, with substrate atoms closer to their bulk terminated positions compared to the clean UHV surface. Acetate is found in a bidentate bridge position, binding through both oxygen atoms to two five-fold titanium atoms such that the molecular plane is along the [001] azimuth. Density functional theory calculations provide adsorption geometries in excellent agreement with experiment. The availability of these structural data will improve the accuracy of charge transport models for DSSC.