Group Consumption, Free Riding, and Informal Reciprocity Agreements

We examine conditions under which group consumption is likely to involve informal and tacit reciprocity agreements rather than formal contracts and the price system. Our model shows that informal reciprocity agreements are more likely to be used when transaction costs of formal agreements are high, the good is relatively inexpensive, each consumer's demand is not too responsive to price changes, the group is likely to continue to interact over time, the consumers are patient, the time between interactions is short, and the group is small and homogeneous. Further, the results suggest that informal sharing agreements are more likely to involve goods that are consumed along with other group benefits, such as conversation and companionship. We conclude by analyzing investments in social capital and discussing the effects of deeper social interactions constrained by norm structures on our results.club; institution; non-market; reciprocal; social capital

Simultaneous fitting of X-ray and neutron diffuse scattering data

Conventional crystallographic refinement uses the Bragg-peak intensities and gives the single-site average crystal structure. Information about short-range order and local order is contained in the diffuse scattering that is distributed throughout reciprocal space. Models of the short-range order in materials can now be automatically refined. The complementarity of X-ray and neutron diffraction data, and the value of simultaneously refining a structural model against both types of data, has long been known. This paper presents the first refinement of a short-range-order model against comprehensive X-ray and neutron diffuse scattering data simultaneously. The sample is the organic molecular crystal benzil, C14H10O2 (for neutron work H is replaced by D). The technique gives new insights into local order in crystalline materials, including the dynamic correlation structure indicative of the dynamics of molecules in the crystalline state, and successfully overcomes limitations of using only the X-ray data set

Size scaling of strength and toughness for 3D printed polymer specimens

To find material systems that offer low density and high strength, stiffness or toughness, hierarchically designed material systems have provided a promising research area. This thesis lays the groundwork for designing efficient micro-architectured material systems by characterizing size effects for 3d printed polymer parts. Two methods were used to analyze data from 3-point bend tests for specimens of varying size: the load-separation method was used for finding the point of crack growth initiation and Bazant’s method was used to find shape independent strength at failure. The strength values were used as inputs for finding size independent material constants within a thermodynamic scaling law model. Such material constants were found to not be universally applicable across the size scales being considered because the scaling law displayed non-monotonic behavior. The strength values showed a local maximum before decreasing at the smallest length scales. These results are compared to similar analytical and experimental results for both quasi-brittle materials and metals. Effects due to fractal crack propagation and specimen homogeneity are ruled out in consideration of the evidence for multiple size effects. Support is provided to show that the PolyJet process produces layers of varying elastic modulus, the thickness of which act as a characteristic length scale and reverse the energetic scaling law. The study concludes with recommendations for further work to confirm this hypothesis

Critical determinants of service quality for the port of cape town users

This research study was motivated by the daily observed operational experiences from the perspective of the researcher’s logistics business. Poor levels of operational service quality were observed in the Port of Cape Town during the 2017/2018 “wind season” which occurs from September to March, where the port lost more than 1200-man hours due to wind delays. The poor levels of operational service quality are further compounded by the effects of the wind delays and its impact on congestion at the port which results in financial loss to importers and exporters and their intermodal service providers. Nearly ninety six percent (96%) of exports from South Africa are by sea, therefore South Africa’s trade with the rest of the world is by sea. Thus, ports are important economic contributors and play an important role for both inbound and outbound logistics. Service quality failures affect business-to-business players in the logistics chain. Port users suffer financial and reputational damage when containers, which are shipped via the port, are delayed due to service quality failures. The purpose of this treatise was to determine what the critical determinants of service quality for the Port of Cape Town users are. To achieve this a conceptual research model was developed, where six variables were identified that have an influence on service quality. The six variables identified are Communication, Competence, Access, Reliability, Understanding/Knowing Customer and Tangibles. A literature review was then conducted to determine what the difference between B2C and B2B operational service quality is. This was done by investigating both the similarities and differences between B2C and B2B and providing a review of service quality and customer satisfaction. Similarly, a literature review was also conducted to investigate the contrasts between international and local port service quality. This was achieved by investigating the importance of ports and an overview of the South African port network. An overview of the Port of Cape Town was then provided where inefficiencies in the Port of Cape Town are discussed. Service quality in selected international ports are then discussed before the chapter was concluded by providing a review of service quality at the port of Cape Town’s two closest international competitors. The methodological approach to the study was quantitative research using a survey strategy to test the conceptual model. Analysis was performed through descriptive and inferential statics. Based on the analysis, the study could conclude by making important managerial recommendations that the management of the Port of Cape Town could implement to improve the level of Operational Service Quality at the port. Some of the recommendations are, that the ports staff should be trained in the importance of proactive communication. Port staff should receive regular training with respect to their operational functions. The port should provide a platform which will allow port users to raise concerns or provide compliments related to container operations or port staff interactions. Before communicating start up times after port stoppages, the port needs to take in to consideration the necessary time required to get staff back to their operational posts and other start-up operations when advising the port reopening time to port users. Port management should implement a better maintenance programme for the container handling equipment as it was the respondent’s perception that the handling equipment used in the port is not always in good working condition

Characterization of Erosion Rates From Two First-Order Watersheds Near Yuma, AZ: Towards an Enhanced Understanding of Alluvial Fan Dynamics

Timing and rates of sediment production and transport in alluvial environments are not well understood. Particularly, are these systems limited by sediment production rates or by sediment transportation rates? Beryllium-10 (10Be) quantification was used to determine long-term bedrock erosion rates, catchment-average erosion rates, and paleo-erosion rates in the Muggins Mountains, an arid drainage basin in southwestern Arizona. Comparing erosion rates at different points in the alluvial system tests for variance in time between sediment production, transportation, and deposition and further allows for characterization of drivers of landscape change. 10Be data indicate that (1) the basins are in dynamic steady state with respect to sediment production and transport, (2) average erosion rate decreases with distance from the sediment source, (3) average erosion rate for each basin varies with time. Findings suggest that rates of sediment transport downstream vary on timescales governed by atmospheric circulation patterns rather than glacial and interglacial cycles, and that the likely primary mechanism of sediment generation in the Muggins Mountains may be salt shattering on different slope aspects of the highlands

Suppression of backscattered diffraction from sub-wavelength ‘moth-eye’ arrays

The eyes and wings of some species of moth are covered with arrays of nanoscale features that dramatically reduce reflection of light. There have been multiple examples where this approach has been adapted for use in antireflection and antiglare technologies with the fabrication of artificial moth-eye surfaces. In this work, the suppression of iridescence caused by the diffraction of light from such artificial regular moth-eye arrays at high angles of incidence is achieved with the use of a new tiled domain design, inspired by the arrangement of features on natural moth-eye surfaces. This bio-mimetic pillar architecture contains high optical rotational symmetry and can achieve high levels of diffraction order power reduction. For example, a tiled design fabricated in silicon and consisting of domains with 9 different orientations of the traditional hexagonal array exhibited a ~96% reduction in the intensity of the ?1 diffraction order. It is suggested natural moth-eye surfaces have evolved a tiled domain structure as it confers efficient antireflection whilst avoiding problems with high angle diffraction. This combination of antireflection and stealth properties increases chances of survival by reducing the risk of the insect being spotted by a predator. Furthermore, the tiled domain design could lead to more effective artificial moth-eye arrays for antiglare and stealth applications

Selenium persistency and speciation in the tissues of lambs following the withdrawal of dietary high-dose selenium-enriched yeast

The objective was to determine the concentration of total selenium (Se) and the proportion of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in post mortem tissues of lambs in the six weeks period following the withdrawal of a diet containing high dose selenized yeast (SY), derived from a specific strain of Saccharomyces cerevisae CNCM (Collection Nationale de Culture de Micro-organism) I-3060. Thirty Texel x Suffolk lambs used in this study had previously received diets (91 days) containing either high dose SY (HSY; 6.30 mg Se/kg DM) or an unsupplemented control (C; 0.13 mg Se/kg DM). Following the period of supplementation all lambs were then offered a complete pelleted diet, without additional Se (0.15 mg Se/kg DM), for 42 days. At enrollment and 21 and 42 days later, five lambs from each treatment were blood sampled, euthanased and samples of heart, liver, kidney and skeletal muscle (Longissimus Dorsi and Psoas Major) tissue were retained. Total Se concentration in whole blood and tissues was significantly (P < 0.001) higher in HSY lambs at all time points that had previously received long term exposure to high dietary concentrations of SY. The distribution of total Se and the proportions of total Se comprised as SeMet and SeCys differed between tissues, treatment and time points. Total Se was greatest in HSY liver and kidney (22.64 and 18.96 mg Se/kg DM, respectively) and SeCys comprised the greatest proportion of total Se. Conversely, cardiac and skeletal muscle (Longissimus Dorsi and Psoas Major) tissues had lower total Se concentration (10.80, 7.02 and 7.82 mg Se/kg DM, respectively) and SeMet was the predominant selenized amino acid. Rates of Se clearance in HSY liver (307 µg Se/day) and kidney (238 µg Se/day) were higher compared with HSY cardiac tissue (120 µg Se/day) and skeletal muscle (20 µg Se/day). In conclusion differences in Se clearance rates were different between tissue types, reflecting the relative metabolic activity of each tissue, and appear to be dependant upon the proportions of total Se comprised as either SeMet or SeCys

Market Power and Cartel Formation: Theory and an Empirical Test

Antitrust enforcement makes it difficult to test theories of cartel formation because most attempts to form cartels are blocked. However, federal laws allow U.S. produce growers to operate marketing cartels through devices called marketing orders. These cartels use quantity controls and quality standards to raise prices on fresh produce. Some growers have adopted marketing orders and others have not. This paper develops and tests a positive theory of the adoption of marketing orders. The theory suggests that growers in a region are more likely to adopt a marketing order if the demand for fresh produce is inelastic, the growers’ market share in the fresh market is large, there are barriers to entry and expansion, the fraction of the output the growers ship to the fresh market is not too large or too small, growers are homogeneous, and large cooperatives exist. Probit analyses support these hypotheses.marketing order; cartel; collusion; empirical; agriculture

Treatment of CD30-Expressing Germ Cell Tumors and Sex Cord Stromal Tumors with Brentuximab Vedotin: Identification and Report of Seven Cases

BACKGROUND: Cytotoxic therapy for relapsed and refractory germ cell tumors or metastatic sex cord stromal tumors is rarely effective and is often accompanied by high adverse event rates. Expression of CD30 has been observed in testicular cancers, and patients with CD30-expressing embryonal carcinomas have worse progression-free survival and overall survival than those with CD30-negative tumors. The objective of this study (NCT01461538) was to characterize the antitumor activity of brentuximab vedotin in patients with CD30-expressing nonlymphomatous malignancies. Enrolled patients included seven patients with relapsed or refractory germ cell tumors or metastatic sex cord stromal tumors described in this case series. MATERIALS AND METHODS: Forty patients with relapsed or refractory germ cell tumors, metastatic sex cord stromal tumors, or testicular tumors were screened for CD30 expression; 14 patients had tumors that expressed CD30. Seven patients with CD30-expressing testicular cancer were enrolled in the treatment study: five patients with germ cell tumors, one patient with a Leydig cell tumor, and one patient with a Sertoli cell tumor. Patients were treated with brentuximab vedotin at initial doses of 1.8 or 2.4 mg/kg every 3 weeks. Response assessments were performed at cycles 2 and 4 and every 4 cycles thereafter while the patient was receiving treatment. RESULTS: Two of seven patients achieved an objective response, including one durable complete response and one partial response at a single time point. Both responding patients had germ cell tumors. Treatment with brentuximab vedotin was generally well tolerated. CONCLUSION: Treatment of relapsed or refractory germ cell tumors with brentuximab vedotin can induce durable responses with a manageable toxicity profile. IMPLICATIONS FOR PRACTICE: This case series of seven patients with relapsed or refractory CD30-expressing germ cell tumors (GCTs) or sex cord stromal tumors demonstrates that brentuximab vedotin has activity against GCTs and is well tolerated in heavily pretreated patients with these aggressive tumor types. One patient achieved a complete response that has been durable for almost 4 years since the discontinuation of treatment with brentuximab vedotin. Therefore, brentuximab vedotin may be a valuable option for physicians who care for this difficult-to-treat patient population

Developing a low-cost beer dispensing robotic system for the service industry

As the prices of commercially available electronic and mechanical components decrease, manufacturers such as Devantech and Revolution Education have made encoded motor controller systems and microcontrollers very accessible to engineers and designers. This has made it possible to design sophisticated robotic and mechatronic systems very rapidly and at relatively low cost. A recent project in the Autonomous Systems Lab at Middlesex University, UK was to design and build a small, automated, robotic bartender based around the 5 litre Heineken 'Draughtkeg' system, which is capable of patrolling a bar and dispensing beer when signalled to by a customer. Because the system was designed as a commercial product, design constraints focused on keeping the build cost down, and so electronic components were sourced from outside companies and interfaced with a bespoke chassis and custom mechanical parts designed and manufactured on site at the University. All the programming was conducted using the proprietary BASIC language, which is freely available from the PicAXE supplier at no cost. This paper will discuss the restrictions involved in building a robot chassis around 'off-theshelf' components, and the issues arising from making the human-machine interaction intuitive whilst only using low-cost ultrasonic sensors. Programming issues will also be discussed, such as the control of accuracy when interfacing a PicAXE microcontroller with a Devantech MD25 Motor Controller board. Public live testing of the system was conducted at the Kinetica Art Fair 2010 event in London and has since been picked up by websites such as Engadget.com and many others. Feedback on the system will be described, as well as the refinements made as a result of these test