Street Food Stand Availability, Density, and Distribution Across Income Levels in Mexico City

Street food stands (SFS) are an understudied element of the food environment. Previous SFS studies have not used a rigorous approach to document the availability, density, and distribution of SFS across neighborhood income levels and points of access in Mexico City. A random sample (n = 761) of street segments representing 20 low-, middle-, and high-income neighborhoods were assessed using geographic information system (GIS) and ground-truthing methods. All three income levels contained SFS. However, SFS availability and density were higher in middle-income neighborhoods. The distribution of SFS showed that SFS were most often found near homes, transportation centers, and worksites. SFS availability near schools may have been limited by local school policies. Additional studies are needed to further document relationships between SFS availability, density, and distribution, and current structures and processes.

Becoming

In this introduction to the special issue the authors craft a critical autoethnography to chronicle their relationship and/to critical autoethnography. They use Michelle Obama’s book and documentary Becoming to reflect on how the critical reflexivity inherent in autoethnographic work can be used to document relationships, moments of revelation, and self-empowerment. They then preview four articles that map experiences of becoming linked to racialized identity, disability, and family.

Automatically Denormalizing Document Relationships

Native XML databases provide no exception to the problem that data may not be easily contained by any single data storage idiom. Many-to-many relationships, in particular, present a unique problem for documents, as strategies for joining across documents are a potential minefield of software maintenance and performance problems. Automatic denormalization shifts the responsibilty for managing relationships to write-time, making an explicit trade-off for simplicity and speed at runtime. This paper discusses existing strategies for managing relationships across documents and explores design patterns and use cases for performing automatic denormalization and their trade-offs.

Estudio del polen de Phaseolus chiapasanus Piper (Leguminosae: Phaseolinae)

In the course of a taxonomical revision of the genus Phaseolus and considering the recently important research realized in the Phaseolus-Vigna complex, where the palynological attributes for the genus were precised, the present paper describes the pollen of Phaseolus chiapasanus Piper. The large-size class pollen grains of Ph. chiapasanus are tricolporate, brevicolpate, pseudo-operculate; semitectate, and widely reticulate. The structure of the infratectum could be considered of the granular-collumelar type. Some of the attributes found in the polen of Ph. Chiapasanus were not known for the genus, though such attributes are commonly found in the subgenus Sigmoidotropis of the genus Vigna. Ph. chiapasanus shows a series of morphological and palynological differences that open the possibility for the creation of a new section within the genus. More detailed studies will definitely by needed to better document relationships to other species of the genus.

Results from the International Halocarbons in Air Comparison Experiment (IHALACE)

The International Halocarbons in Air Comparison Experiment (IHALACE) was conducted to document relationships between calibration scales among various laboratories that measure atmospheric greenhouse and ozone depleting gases. This study included trace gases such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs), as well as nitrous oxide, methane, sulfur hexafluoride, very short-lived halocompounds, and carbonyl sulfide. Many of these gases are present in the unpolluted atmosphere at pmol mol−1 (parts per trillion) or nmol mol−1 (parts per billion) levels. Six stainless steel cylinders containing natural and modified natural air samples were circulated among 19 laboratories. Results from this experiment reveal relatively good agreement (within a few percent) among commonly used calibration scales. Scale relationships for some gases, such as CFC-12 and CCl4, were found to be consistent with those derived from estimates of global mean mole fractions, while others, such as halon-1211 and CH3Br, revealed discrepancies. The transfer of calibration scales among laboratories was problematic in many cases, meaning that measurements tied to a particular scale may not, in fact, be compatible. Large scale transfer errors were observed for CH3CCl3 (10–100%) and CCl4 (2–30%), while much smaller scale transfer errors (< 1%) were observed for halon-1211, HCFC-22, and HCFC-142b. These results reveal substantial improvements in calibration over previous comparisons. However, there is room for improvement in communication and coordination of calibration activities with respect to the measurement of halogenated and related trace gases.

TOPICVIEW: VISUAL ANALYSIS OF TOPIC MODELS AND THEIR IMPACT ON DOCUMENT CLUSTERING

We present a new approach for analyzing topic models using visual analytics. We have developed TopicView, an application for visually comparing and exploring multiple models of text corpora, as a prototype for this type of analysis tool. TopicView uses multiple linked views to visually analyze conceptual and topical content, document relationships identified by models, and the impact of models on the results of document clustering. As case studies, we examine models created using two standard approaches: Latent Semantic Analysis (LSA) and Latent Dirichlet Allocation (LDA). Conceptual content is compared through the combination of (i) a bipartite graph matching LSA concepts with LDA topics based on the cosine similarities of model factors and (ii) a table containing the terms for each LSA concept and LDA topic listed in decreasing order of importance. Document relationships are examined through the combination of (i) side-by-side document similarity graphs, (ii) a table listing the weights for each document's contribution to each concept/topic, and (iii) a full text reader for documents selected in either of the graphs or the table. The impact of LSA and LDA models on document clustering applications is explored through similar means, using proximities between documents and cluster exemplars for graph layout edge weighting and table entries. We demonstrate the utility of TopicView's visual approach to model assessment by comparing LSA and LDA models of several example corpora.

Results from the International Halocarbons in Air Comparison Experiment (IHALACE)

The International Halocarbons in Air Comparison Experiment (IHALACE) was conducted to document relationships between calibration scales among various laboratories that measure atmospheric greenhouse and ozone depleting gases. Six stainless steel cylinders containing natural and modified natural air samples were circulated among 19 laboratories. Results from this experiment reveal relatively good agreement among commonly used calibration scales for a number of trace gases present in the unpolluted atmosphere at pmol mol−1 (parts per trillion) levels, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Some scale relationships were found to be consistent with those derived from bi-lateral experiments or from analysis of atmospheric data, while others revealed discrepancies. The transfer of calibration scales among laboratories was found to be problematic in many cases, meaning that measurements tied to a common scale may not, in fact, be compatible. These results reveal substantial improvements in calibration over previous comparisons. However there is room for improvement in communication and coordination of calibration activities with respect to the measurement of halogenated and related trace gases.