High-Temperature Alkali Vapor Cells with Anti-Relaxation Surface Coatings

Antirelaxation surface coatings allow long spin relaxation times in alkali-metal cells without buffer gas, enabling faster diffusion of the alkali atoms throughout the cell and giving larger signals due to narrower optical linewidths. Effective coatings were previously unavailable for operation at temperatures above 80 C. We demonstrate that octadecyltrichlorosilane (OTS) can allow potassium or rubidium atoms to experience hundreds of collisions with the cell surface before depolarizing, and that an OTS coating remains effective up to about 170 C for both potassium and rubidium. We consider the experimental concerns of operating without buffer gas and with minimal quenching gas at high vapor density, studying the stricter need for effective quenching of excited atoms and deriving the optical rotation signal shape for atoms with resolved hyperfine structure in the spin-temperature regime. As an example of a high-temperature application of antirelaxation coated alkali vapor cells, we operate a spin-exchange relaxation-free atomic magnetometer with sensitivity of 6 fT/sqrt(Hz) and magnetic linewidth as narrow as 2 Hz.Comment: 8 pages, 5 figures. The following article appeared in Journal of Applied Physics and may be found at http://link.aip.org/link/?jap/106/11490

First-principles quantum dynamics for fermions: Application to molecular dissociation

We demonstrate that the quantum dynamics of a many-body Fermi-Bose system can be simulated using a Gaussian phase-space representation method. In particular, we consider the application of the mixed fermion-boson model to ultracold quantum gases and simulate the dynamics of dissociation of a Bose-Einstein condensate of bosonic dimers into pairs of fermionic atoms. We quantify deviations of atom-atom pair correlations from Wick's factorization scheme, and show that atom-molecule and molecule-molecule correlations grow with time, in clear departures from pairing mean-field theories. As a first-principles approach, the method provides benchmarking of approximate approaches and can be used to validate dynamical probes for characterizing strongly correlated phases of fermionic systems.Comment: Final published versio

African origins of rice cultivation in the Black Atlantic

A diáspora africana era tanto de plantas como de pessoas. O arroz (Oryza Glaberrima) permitiu a difusão de plantas e sistemas agrícolas africanos que amoldaram o ambiente, preferências de comida, economias e identidade cultural durante a era de escravidão. No século XVIII o cereal era largamente cultivado, da Carolina do Sul, ao Brasil. Cultivado por escravos como também pelos "marrons", tanto em plantações para subsistência como para exportação, o cultivo de arroz acompanhou o estabelecimento africano nas Américas. Este artigo revisa os sistemas de conhecimento indígenas africano e americanos (América atlântica). Com métodos e práticas idênticos, escravos da África ocidental adaptaram o cultivo às condições novas nas Américas. Enfocando a origem Africana do cultivo do arroz na Carolina do Sul, este trabalho busca recuperar uma narrativa significante do tráfico atlântico de escravos.The African diaspora was one of plants as well as people. Rice (Oryza glaberrima) led the diffusion of African plants and agricultural systems that shaped environment, food preferences, economies and cultural identity during the era of plantation slavery. By the eighteenth century the cereal was widely established from South Carolina to Brazil in the Americas. Grown by slaves as well as maroons, on plantations for subsistence as well as for export, rice cultivation accompanied African settlement of the Americas. This article reviews the indigenous knowledge systems that informed the cultivation of rice along the African as well as American Atlantic. With identical methods and practices, slaves from West Africa adapted a favored dietary staple to new conditions in the Americas, thereby ensuring the cereal’s enduring significance in Diaspora cuisines. In illuminating the African origins of Carolina rice beginnings, this paper aims to recover a significant narrative of the Atlantic slave trad

Energy intake and appetite responses following manipulation of fluid balance and intake

Fluid intake and regulation are implicated in the control of energy balance and appetite. The studies in this thesis have examined the effects of fluid manipulation on appetite and energy intake. Fifty-eight young, predominantly Caucasian males were recruited to five studies. The age, height and body mass of the subjects were: 24.9 ± 3.8 y, 1.79 ± 0.1 m, 80.1 ± 14.8 kg (mean ± SD) respectively. In Chapter 3, 13 h of hypohydration after exercise in the heat did not influence energy intake at an ad-libitum buffet meal (P=0.436) compared to a euhydrated trial, although greater thirst (P<0.001) and lower fullness (P<0.01) was reported in the hypohydration trial. Chapter 4 demonstrated that there was no difference in energy intake or appetite after 24 h of hypohydration either with or without fluid during a semi-solid ad-libitum breakfast. Thirst and fluid intake were greater during the hypohydrated with fluid (HYPO-F; 618 (251) mL) than the euhydrated with fluid (EU-F; 400 (247) mL) trials (P<0.01). Chapter 5 and 6 showed that a bolus of water (500 mL) immediately before an ad-libitum porridge breakfast reduced energy intake in both healthy and overweight and obese subjects (P<0.001). The water preload increased fullness and decreased hunger compared to pre-trial in both studies (P<0.001). In Chapter 7, 75 minutes before an ad-libitum lunch a post-exercise milk (MILK) based drink reduced energy intake (6746 (2035) kJ) compared to an isoenergetic flavoured carbohydrate (CHO) and water based drink (7762 (1921) kJ; 7672 (2005) kJ) (P<0.05). This thesis has shown that when subjects are hypohydrated, either after exercise or after 24 h of fluid restriction energy intake is not different at an ad-libitum meal. However, there is an increased thirst and subsequent fluid intake before an ad-libitum meal (chapter 3 and 4). This effect was more acutely displayed when a bolus of water was provided immediately before an ad-libitum breakfast meal and subsequently decreased energy intake in both normal and overweight/ obese subjects (chapter 5 and 6). The possible mechanism for this was gastric fill and distension creating satiety before a meal. Chapter 7 has showed that when subjects consume isoenergetic drinks with different energy densities (milk vs CHO and water), before an ad-libitum lunch, energy intake was decreased when milk was consumed. Milk having an increased energy density due to larger protein fractions (casein) may further explain the decrease in energy intake found in chapters 5 and 6 by a similar mechanism. Therefore, gastric fill before a meal decreases ad-libitum energy intake by either the intake of water immediately before a meal or by milk as a more delayed response (75 min). The hydration status however, did not affect energy intake directly in our finding, although it did affect subsequent fluid ingestion, which may have affected findings in chapters 3 and 4

Quantum optical waveform conversion

Currently proposed architectures for long-distance quantum communication rely on networks of quantum processors connected by optical communications channels [1,2]. The key resource for such networks is the entanglement of matter-based quantum systems with quantum optical fields for information transmission. The optical interaction bandwidth of these material systems is a tiny fraction of that available for optical communication, and the temporal shape of the quantum optical output pulse is often poorly suited for long-distance transmission. Here we demonstrate that nonlinear mixing of a quantum light pulse with a spectrally tailored classical field can compress the quantum pulse by more than a factor of 100 and flexibly reshape its temporal waveform, while preserving all quantum properties, including entanglement. Waveform conversion can be used with heralded arrays of quantum light emitters to enable quantum communication at the full data rate of optical telecommunications.Comment: submitte

Outsourcing labour to the cloud

Various forms of open sourcing to the online population are establishing themselves as cheap, effective methods of getting work done. These have revolutionised the traditional methods for innovation and have contributed to the enrichment of the concept of 'open innovation'. To date, the literature concerning this emerging topic has been spread across a diverse number of media, disciplines and academic journals. This paper attempts for the first time to survey the emerging phenomenon of open outsourcing of work to the internet using 'cloud computing'. The paper describes the volunteer origins and recent commercialisation of this business service. It then surveys the current platforms, applications and academic literature. Based on this, a generic classification for crowdsourcing tasks and a number of performance metrics are proposed. After discussing strengths and limitations, the paper concludes with an agenda for academic research in this new area

Geometric reasoning via internet crowdsourcing

The ability to interpret and reason about shapes is a peculiarly human capability that has proven difficult to reproduce algorithmically. So despite the fact that geometric modeling technology has made significant advances in the representation, display and modification of shapes, there have only been incremental advances in geometric reasoning. For example, although today's CAD systems can confidently identify isolated cylindrical holes, they struggle with more ambiguous tasks such as the identification of partial symmetries or similarities in arbitrary geometries. Even well defined problems such as 2D shape nesting or 3D packing generally resist elegant solution and rely instead on brute force explorations of a subset of the many possible solutions. Identifying economic ways to solving such problems would result in significant productivity gains across a wide range of industrial applications. The authors hypothesize that Internet Crowdsourcing might provide a pragmatic way of removing many geometric reasoning bottlenecks.This paper reports the results of experiments conducted with Amazon's mTurk site and designed to determine the feasibility of using Internet Crowdsourcing to carry out geometric reasoning tasks as well as establish some benchmark data for the quality, speed and costs of using this approach.After describing the general architecture and terminology of the mTurk Crowdsourcing system, the paper details the implementation and results of the following three investigations; 1) the identification of "Canonical" viewpoints for individual shapes, 2) the quantification of "similarity" relationships with-in collections of 3D models and 3) the efficient packing of 2D Strips into rectangular areas. The paper concludes with a discussion of the possibilities and limitations of the approach

Validation of purdue engineering shape benchmark clusters by crowdsourcing

The effective organization of CAD data archives is central to PLM and consequently content based retrieval of 2D drawings and 3D models is often seen as a "holy grail" for the industry. Given this context, it is not surprising that the vision of a "Google for shape", which enables engineers to search databases of 3D models for components similar in shape to a query part, has motivated numerous researchers to investigate algorithms for computing geometric similarity. Measuring the effectiveness of the many approaches proposed has in turn lead to the creation of benchmark datasets against which researchers can compare the performance of their search engines. However to be useful the datasets used to measure the effectiveness of 3D retrieval algorithms must not only define a collection of models, but also provide a canonical specification of their relative similarity. Because the objective of shape retrieval algorithms is (typically) to retrieve groups of objects that humans perceive as "similar" these benchmark similarity relationships have (by definition) to be manually determined through inspection

Mining Newsorthy Topics from Social Media

Newsworthy stories are increasingly being shared through social networking platforms such as Twitter and Reddit, and journal-ists now use them to rapidly discover stories and eye-witness accounts. We present a technique that detects “bursts” of phrases on Twitter that is designed for a real-time topic-detection system. We describe a time-dependent variant of the classic tf-idf approach and group together bursty phrases that often appear in the same messages in order to identify emerging topics. We demonstrate our methods by analysing tweets corresponding to events drawn from the worlds of politics and sport. We created a user-centred “ground truth” to evaluate our methods, based on mainstream media accounts of the events. This helps ensure our methods remain practical. We compare several clustering and topic ranking methods to discover the characteristics of news-related collections, and show tha t different strategies are needed to detect emerging topics within them. We show that our methods successfully detect a range of different topics for each event and can retrieve messages (for example, tweets) that represent each topic for the user