bluuebunny/crossref_metadata_2025 huggingface dataset:
Sonic hedgehog is indirectly required for intraretinal axon pathfinding by regulating chemokine expression in the optic stalk
Authors: Hörndli Cornelia Stacher , Chien Chi-Bin
Published: June 2012

Successful axon pathfinding requires both correct patterning of tissues, which will later harbor axonal tracts, and precise localization of axon guidance cues along these tracts at the time of axon outgrowth. Retinal ganglion cell (RGC) axons grow towards the optic disc in the central retina, where they turn to exit the eye through the optic nerve. Normal patterning of the optic disc and stalk and the expression of guidance cues at this choice point are necessary for the exit of RGC axons out of the eye. Sonic hedgehog (Shh) has been implicated in both patterning of ocular tissue and direct guidance of RGC axons. Here, we examine the precise spatial and temporal requirement for Hedgehog (Hh) signaling for intraretinal axon pathfinding and show that Shh acts to pattern the optic stalk in zebrafish but does not guide RGC axons inside the eye directly. We further reveal an interaction between the Hh and chemokine pathways for axon guidance and show that cxcl12a functions downstream of Shh and depends on Shh for its expression at the optic disc. Together, our results support a model in which Shh acts in RGC axon pathfinding indirectly by regulating axon guidance cues at the optic disc through patterning of the optic stalk.
Supply Chain Performance Under Market Valuation: An Operational Approach to Restore Efficiency
Authors: Lai Guoming , Xiao Wenqiang , Yang Jun
Published: June 2012

Based on a supply chain framework, we study the stocking decision of a downstream buyer who receives private demand information and has the incentive to influence her capital market valuation. We first characterize a market equilibrium under a general, single buyback contract. We show that the buyer's stocking decision can be distorted in equilibrium. Such a downstream stocking distortion hurts the buyer firm's own performance, and it also influences the performances of the supplier and the supply chain. We further reveal scenarios where full supply chain efficiency cannot be reached under any single buyback contract. Then, focusing on contract design, we characterize conditions under which a menu of buyback contracts can prevent downstream stocking distortion and restore full efficiency in the supply chain. Our study demonstrates that in a supply chain context, a firm's incentive to undertake real economic activities to influence capital market valuation can potentially be resolved through operational means.

This paper was accepted by Yossi Aviv, operations management.
Large-Scale Service Marketplaces: The Role of the Moderating Firm
Authors: Allon Gad , Bassamboo Achal , Çil Eren B.
Published: June 2012

Recently, large-scale, Web-based service marketplaces, where many small service providers compete among themselves in catering to customers with diverse needs, have emerged. Customers who frequent these marketplaces seek quick resolutions and thus are usually willing to trade prices with waiting times. The main goal of this paper is to discuss the role of the moderating firm in facilitating information gathering, operational efficiency, and communication among agents in service marketplaces. Surprisingly, we show that operational efficiency may be detrimental to the overall efficiency of the marketplace. Furthermore, we establish that to reap the “expected” gains of operational efficiency, the moderating firm may need to complement the operational efficiency by enabling communication among its agents. The study emphasizes the scale of such marketplaces and the impact it has on the outcomes.

This paper was accepted by Yossi Aviv, operations management.
The Visible Hand? Demand Effects of Recommendation Networks in Electronic Markets
Authors: Oestreicher-Singer Gal , Sundararajan Arun
Published: June 2012

Online commercial interactions have increased dramatically over the last decade, leading to the emergence of networks that link the electronic commerce landing pages of related products to one another. Our paper conjectures that the explicit visibility of such “product networks”can alter demand spillovers across their constituent items. We test this conjecture empirically using data about the copurchase networks and demand levels associated with more than 250,000 interconnected books offered on Amazon.com over the period of one year while controlling for alternative explanations of demand correlation using a variety of approaches. Our findings suggest that on average the explicit visibility of a copurchase relationship can lead to up to an average threefold amplification of the influence that complementary products have on each others' demand levels. We also find that newer and more popular products “use” the attention they garner from their network position more efficiently and that diversity in the sources of spillover further amplifies the demand effects of the recommendation network. Our paper presents new evidence quantifying the role of network position in electronic markets and highlights the power of basing (virtual) shelf position on consumer preferences that are explicitly revealed through shared purchasing patterns.

This paper was accepted by Pradeep Chintagunta, marketing.
Aspirational Preferences and Their Representation by Risk Measures
Authors: Brown David B. , Giorgi Enrico De , Sim Melvyn
Published: June 2012

We consider choice over uncertain, monetary payoffs and study a general class of preferences. These preferences favor diversification, except perhaps on a subset of sufficiently disliked acts over which concentration is instead preferred. This structure encompasses a number of known models (e.g., expected utility and several variants under a concave utility function). We show that such preferences share a representation in terms of a family of measures of risk and targets. Specifically, the choice function is equivalent to selection of a maximum index level such that the risk of beating the target at that level is acceptable. This representation may help to uncover new models of choice. One that we explore in detail is the special case when the targets are bounded. This case corresponds to a type of satisficing and has descriptive relevance. Moreover, the model is amenable to large-scale optimization.

This paper was accepted by Teck Ho, decision analysis.
Pathwise Optimization for Optimal Stopping Problems
Authors: Desai Vijay V. , Farias Vivek F. , Moallemi Ciamac C.
Published: June 2012

We introduce the pathwise optimization (PO) method, a new convex optimization procedure to produce upper and lower bounds on the optimal value (the “price”) of a high-dimensional optimal stopping problem. The PO method builds on a dual characterization of optimal stopping problems as optimization problems over the space of martingales, which we dub the martingale duality approach. We demonstrate via numerical experiments that the PO method produces upper bounds of a quality comparable with state-of-the-art approaches, but in a fraction of the time required for those approaches. As a by-product, it yields lower bounds (and suboptimal exercise policies) that are substantially superior to those produced by state-of-the-art methods. The PO method thus constitutes a practical and desirable approach to high-dimensional pricing problems. Furthermore, we develop an approximation theory relevant to martingale duality approaches in general and the PO method in particular. Our analysis provides a guarantee on the quality of upper bounds resulting from these approaches and identifies three key determinants of their performance: the quality of an input value function approximation, the square root of the effective time horizon of the problem, and a certain spectral measure of “predictability” of the underlying Markov chain. As a corollary to this analysis we develop approximation guarantees specific to the PO method. Finally, we view the PO method and several approximate dynamic programming methods for high-dimensional pricing problems through a common lens and in doing so show that the PO method dominates those alternatives.

This paper was accepted by Wei Xiong, stochastic models and simulation.
Firm-Specific, Industry-Specific, and Occupational Human Capital and the Sourcing of Knowledge Work
Authors: Mayer Kyle J. , Somaya Deepak , Williamson Ian O.
Published: June 2012

Whereas capability differences are known to impact governance decisions, what drives heterogeneity in firm capabilities? We propose that capability differences may arise from governance choices related to the focal activity and study how firms accumulate capabilities in the firm-specific, industry-specific, and occupational human capital necessary to perform knowledge work. We theorize that prior outsourcing decisions influence the development of firm- and industry-specific human capital and that buyer–supplier differences in the management of skilled employees can produce systematic differences in capabilities based on occupational human capital. Additionally, we explore some contingencies in the development of these types of human capital and their impacts on outsourcing knowledge work. These propositions are tested with a unique data set on the outsourcing of legal work involved in filing patents (i.e., patent prosecution).
Capabilities, Transaction Costs, and Firm Boundaries
Authors: Argyres Nicholas S. , Zenger Todd R.
Published: June 2012

Although the literature on firm boundaries has been greatly influenced by transaction cost economics, strategy scholars often emphasize the importance of capabilities considerations in these decisions. This has led to a debate that, we suggest, has generated more heat than light. We argue that the two sets of considerations are in fact so intertwined dynamically that treating them as independent, competitive explanations is fundamentally misleading. We offer a theoretical synthesis of transaction cost and capabilities approaches to firm boundaries that seeks to overcome each approach's limitations and provides a unified and logically consistent understanding of boundary decisions.
Filling or Abusing the Institutional Void? Ownership and Management Control of Public Family Businesses in an Emerging Market
Authors: Luo Xiaowei Rose , Chung Chi-Nien
Published: June 2012

Despite increased attention given to family firms in the theory of organization and management, the value of family governance in emerging markets is not clearly understood. We draw insights from agency and institutional economics perspectives to address the debate on whether family governance fills or abuses the void left by weaker market and legal institutions. We propose a dual focus on the pattern of family control and weak institutions to reconcile these opposed assessments. We analyze how various combinations of family control over ownership, strategy, and operations yield different benefits and costs for the operational performance of firms in the absence of strong market and legal institutions. The uneven development of market institutions across industries and the impact of independent directors reinforce the importance of separating different patterns of family control. We find support for our hypotheses when tested on a data set consisting of all publicly listed firms in Taiwan between 1996 and 2005. Our study contributes to a deeper understanding of family businesses in emerging markets, highlights the importance of weak institutions in shaping relative agency costs, and illuminates the differential effects of independent directors.
Double Victimization in the Workplace: Why Observers Condemn Passive Victims of Sexual Harassment
Authors: Diekmann Kristina A. , Walker Sheli D. Sillito , Galinsky Adam D. , Tenbrunsel Ann E.
Published: June 2012

Five studies explore observers' condemnation of passive victims. Studies 1 and 2 examine the role of observers' behavioral forecasts in condemning passive victims of sexual harassment. Observers generally predicted that they would engage in greater confrontation than victims typically do. More importantly, the more confrontation participants predicted they would engage in, the more they condemned the passive victim, and the less willing they were to recommend the victim for a job and to work with her. Study 3 identifies the failure to consider important motivations likely experienced by victims—and that contribute to their passivity—as an important driver of behavioral forecasting errors. Having forecasters reflect on motivations normally experienced but not typically forecast produced behavioral predictions that were more consistent with the actual passive behavior of sexual harassment victims. Studies 4 and 5 reduce condemnation of passive sexual harassment victims by highlighting important motivations likely experienced by those victims (Study 4) and by having participants recall a past experience of not acting when being intimidated in the workplace, a situation related but distinct from sexual harassment (Study 5). The results from these studies add insights into the causes and consequences of victim condemnation and help explain why passivity in the face of harassment—the predominant response—is subject to so much scorn.
The Impact of Membership Overlap on Growth: An Ecological Competition View of Online Groups
Authors: Wang Xiaoqing , Butler Brian S. , Ren Yuqing
Published: June 2012

The dominant narrative of the Internet has been one of unconstrained growth, abundance, and plenitude. It is in this context that new forms of organizing, such as online groups, have emerged. However, the same factors that underlie the utopian narrative of Internet life also give rise to numerous online groups, many of which fail to attract participants or to provide significant value. This suggests that despite the potential transformative nature of modern information technology, issues of scarcity, competition, and context may remain critical to the performance and functioning of online groups. In this paper, we draw from organizational ecology theories to develop an ecological view of online groups to explain how overlapping membership among online groups causes intergroup competition for member attention and affects a group's ability to grow. Hypotheses regarding the effects of group size, age, and membership overlap on growth are proposed and tested with data from a 64-month, longitudinal sample of 240 online discussion groups. The analysis shows that sharing members with other groups reduced future growth rates, suggesting that membership overlap puts competitive pressure on online groups. Our results also suggest that, compared with smaller and younger groups, larger and older groups experience greater difficulty in growing their membership. In addition, larger groups were more vulnerable to competitive pressure than smaller groups: larger groups experienced greater difficulty in growing their membership than smaller groups as competition intensified. Overall, our findings show how an abundance of opportunities afforded by technologies can create scarcity in user time and effort, which increases competitive pressure on online groups. Our ecological view extends organizational ecology theory to new organizational forms online and highlights the importance of studying the competitive environment of online groups.
Do Women Choose Different Jobs from Men? Mechanisms of Application Segregation in the Market for Managerial Workers
Authors: Barbulescu Roxana , Bidwell Matthew
Published: June 2012

This paper examines differences in the jobs for which men and women apply in order to better understand gender segregation in managerial jobs. We develop and test an integrative theory of why women might apply to different jobs than men. We note that constraints based on gender role socialization may affect three determinants of job applications: how individuals evaluate the rewards provided by different jobs, whether they identify with those jobs, and whether they believe that their applications will be successful. We then develop hypotheses about the role of each of these decision factors in mediating gender differences in job applications. We test these hypotheses using the first direct comparison of how similarly qualified men and women apply to jobs, based on data on the job searches of MBA students. Our findings indicate that women are less likely than men to apply to finance and consulting jobs and are more likely to apply to general management positions. These differences are partly explained by women’s preference for jobs with better anticipated work–life balance, their lower identification with stereotypically masculine jobs, and their lower expectations of job offer success in such stereotypically masculine jobs. We find no evidence that women are less likely to receive job offers in any of the fields studied. These results point to some of the ways in which gender differences can become entrenched through the long-term expectations and assumptions that job candidates carry with them into the application process.
A Question of Legitimacy? A Dynamic Perspective on Multinational Firm Control
Authors: Brenner Barbara , Ambos Björn
Published: June 2012

The control and coordination of a network of geographically and culturally dispersed subsidiaries is one of the most prominent challenges in international management. However, many empirical findings on the effectiveness of various control mechanisms and combinations thereof are still counterintuitive. This study uses longitudinal case studies and cross-sectional interview data to extend control theory by examining why, how, and in what sequence large multinational firms (MNCs) implement controls in their networks of foreign subsidiaries. Our analysis draws from literature on institutional theory, embeddedness, and organizational power to demonstrate that MNC headquarters need to overcome institutional duality when implementing their controls abroad. We find that headquarters do so by using social controls, primarily as a way of legitimizing and institutionalizing their process and output controls that are implemented subsequently.
The Old Testament "Apocrypha" in Jerome's Canonical Theory
Authors: Gallagher Edmon L.
Published: June 2012

In his preface to Samuel and Kings (the Prologus Galeatus ), Jerome sets forth a theory of the Old Testament canon that allows for no room between the canonical books and the apocrypha. However, Jerome elsewhere maintained a more neutral or even positive view of some of the non-canonical books, even accepting their use within the ecclesiastical liturgy. Jerome's seemingly inconsistent attitude toward some books he classifies as "apocrypha" has led scholars to posit a development in Jerome's canonical theory, such that his earlier position was accepting of books that he later excluded, and to suppose that Jerome's use of the word "apocrypha" in the Prologus Galeatus relied on a neutral definition of the term. This paper examines the evidence for these claims and finds them wanting. While Jerome consistently regarded the books labeled "apocrypha" in the Prologus Galeatus as outside the canon, he chose to propagate an especially harsh judgment against these books especially in this preface. The confusion arising from Jerome's comments may be explained as a consequence of a multi-faceted plan to realign the church's Old Testament with the Hebrew Bible, a plan that Jerome articulates only partially on any given occasion.
Emerging Technologies and Their Impact on Disability
Authors: Wise Paul H.
Published: June 2012

Technological innovation is transforming the prevalence and functional impact of child disability, the scale of social disparities in child disability, and perhaps the essential meaning of disability in an increasingly technology-dominated world. In this article, Paul Wise investigates several specific facets of this transformation. He begins by showing how technological change influences the definition of disability, noting that all technology attempts to address some deficiency in human capacity or in the human condition. Wise then looks at the impact of technology on childhood disabilities. Technical improvements in the physical environment, such as better housing, safer roads, and poison-prevention packaging, have significantly reduced childhood injury and disability. Other technological breakthroughs, such as those that identify genetic disorders that may lead to pregnancy termination, raise difficult moral and ethical issues. Technologies that identify potential health risks are also problematic in the absence of any efficient treatment. Wise stresses the imbalance in the existing health care delivery system, which is geared toward treating childhood physical illnesses that are declining in prevalence at a time when mental and emotional conditions, many of which are not yet well understood, are on the rise. This mismatch, Wise says, poses complex challenges to caring for disabled children, particularly in providing them with highly coordinated and integrated systems of care. Technology can also widen social disparities in health care for people, including children with disabilities. As Wise observes, efficacy—the ability of a technology to change health outcomes —is key to understanding the relationship of technology to social disparities. As technological innovation enhances efficacy, access to that technology becomes more important. Health outcomes may improve for those who can afford the technology, for example, but not for others. Hence, as efficacy grows, so too does the burden on society to provide access to technology equitably to all those in need. Without such access, technological innovation will likely expand disparities in child outcomes rather than reduce them.
Childhood Health: Trends and Consequences over the Life Course
Authors: Delaney Liam , Smith James P.
Published: June 2012

This article first documents evidence on the changing prevalence of childhood physical and mental health problems, focusing on the development of childhood health conditions in the United States. Authors Liam Delaney and James Smith present evidence on the changing prevalence of childhood chronic conditions over time using recalled data as well as contemporaneous accounts of these childhood health problems. The raw data from both sources show sharp increases in the prevalence of most childhood physical health problems (such as asthma, allergies, respiratory problems, and migraines) over time. However, inferring trends is difficult because such data are also consistent with improved detection of childhood disease, and many of the causes of childhood disease have not worsened over time. Conclusions about rapidly rising rates of childhood physical health problems over time are premature at best, especially concerning the magnitude of trends. Documenting real changes in the prevalence of specific diseases is a high-priority research topic. In contrast, the evidence is much stronger that childhood mental health problems are becoming worse. The authors next present new evidence on the effects of early childhood physical and mental problems on health and economic status in adulthood. They find that both childhood physical and mental health problems contribute significantly to poorer adult health. However, they also find that childhood mental health problems have much larger impacts than do childhood physical health problems on four critical areas of socioeconomic status as an adult: education, weeks worked per year, individual earnings, and family income. Finally, the authors examine evidence regarding the efficacy of early mental health treatment for children in terms of promoting good health later on. Existing studies suggest that a combination of cognitive behavioral therapy and medication appears to be effective in the treatment of both anxiety and depression in children. However, much more research is needed on the efficacy of these childhood interventions into adulthood. Clinical trials have been too short to evaluate the long-term impacts of various forms of treatment, and these impacts are definitively long term.
The Changing Landscape of Disability in Childhood
Authors: Halfon Neal , Houtrow Amy , Larson Kandyce , Newacheck Paul W.
Published: June 2012

Americans' perceptions of childhood disability have changed dramatically over the past century, as have their ideas about health and illness, medical developments, threats to children's health and development, and expectations for child functioning. Neal Halfon, Amy Houtrow, Kandyce Larson, and Paul Newacheck examine how these changes have influenced the risk of poor health and disability and how recent policies to address the needs of children with disabilities have evolved. The authors examine the prevalence in the United States of childhood disability and of the conditions responsible for impairment, as well as trends in the prevalence of chronic conditions associated with disability. They find that childhood disability is increasing and that emotional, behavioral, and neurological disabilities are now more prevalent than physical impairments. They stress the importance of, and lack of progress in, improving socioeconomic disparities in disability prevalence, as well as the need for better measures and greater harmonization of data and data sources across different child-serving agencies and levels of government. They call on policy makers to strengthen existing data systems to advance understanding of the causes of childhood disabilities and guide the formulation of more strategic, responsive, and effective policies, programs, and interventions. The authors offer a new and forward-looking definition of childhood disability that reflects emerging and developmentally responsive notions of childhood health and disability. They highlight the relationship between health, functioning, and the environment; the gap in function between a child's abilities and the norm; and how that gap limits the child's ability to engage successfully with his or her world. Their definition also recognizes the dynamic nature of disability and how the experience of disability can be modified by the child's environment.
Global Trade and Swahili Cosmopolitan Material Culture: Chinese-Style Ceramic Shards from Sanje ya Kati and Songo Mnara (Kilwa, Tanzania)
Authors: Zhao Bing
Published: June 2012

This article deals with Chinese-style ceramic shards recently excavated from Songo Mnara and Sanje ya Kati, two insular medieval stonetown sites in Kilwa Bay, Tanzania. The author argues for a regional approach that better accommodates the complexity and particularity of the diffusion and consumption of Chinese ceramics in what is considered a semi-periphery within the Indian Ocean world-system. The article presents a critical synthesis of a number of existing studies, and explores the evaluative potential of density and comparisons with larger-volume regional commodities as tools of analy-sis for Chinese-style ceramic diffusion in the western Indian Ocean.
From the Imperial Court to the International Art Market: Jingdezhen Porcelain Production as Global Visual Culture
Authors: Huang Ellen
Published: June 2012

Abstract: This article describes the emergence, circulation, and provenance of major visual sources on Jingdezhen ceramic history and production. Beginning with the album referred to as "Taoye tu" (Pictures of porcelain production) in eighteenth-century Qing court documents, it follows the dissemination of the visual genre from the Qing imperial court to European, Japanese, and North American consumers across various mediums and disparate political units. Rather than analyze them as disparate genres, this article proposes to view Qing court paintings, export art, woodblock prints, and foreign translations as global historical phenomena, in order to show the existence of a shared visual culture in which production was the primary pictorial theme.
La Theorie de la Chiasmatypie
Authors: Koszul Romain , Zickler Denise
Published: June 2012

First published in 1909 in La Cellule, F. A. Janssens’s “The chiasmatype theory. A new interpretation of the maturation divisions” proved controversial and was for several decades resisted by many geneticists and cytologists. In this month’s Perspectives, Koszul et al. revisit Janssens's findings and the surrounding controversies.

Here, translated for the first time in English, GENETICS republishes the original Janssens’s article. The article is presented as closely as possible to the original publication’s format and style.2 GENETICS wishes to thank Romain Koszul and Denise Zickler for their labors in presenting the scientific community with this new translation.
A concentração e a quantidade de micronutrientes e de alumínio no cafeeiro, Coffea arabica, L., variedade mundo novo (B.Rodr.) Choussy, aos dez anos de idade
Authors: Catani R.A. , Pellegrino D. , Bittencourt V.C. , Jacintho A.O. , Graner C.A.F.
Published: June 2012

O presente trabalho relata os dados obtidos sôbre a concentração e a quantidade de micronutrientes, boro (B), cloro (Cl), cobre (Cu), ferro (Fe), manganês (Mn), molibdênio (Mo) e zinco (Zn), no tronco, ramos, fôlhas e frutos do cafeeiro, Coffea arabica, L., variedade mundo novo (B.Rodr.) Choussy, aos dez anos de idade e crescendo em solo latosólico da Escola Superior de Agricultura "Luiz de Queiroz", em Piracicaba. Além dos micronutrientes, são apresentados dados sobre a concentração e a quantidade de alumínio, nas citadas partes do cafeeiro.
Técnica de réplica de carbono para o estudo da superfície de fôlhas de plantas ao microscópio eletrônico
Authors: Santos Helena de Souza , Crocomo Otto J. , Neptune Andre M. Louis
Published: June 2012

O presente trabalho apresenta um método de réplica de superfície para o estudo da estrutura das fôlhas de vegetais ao microscípio eletrônico. O método permitiu a observação do mesmo tipo de estrutura observada por outros autores na superfície das fôlhas de couve (Brassica oleracea). O método permitiu observar que nas superfícies das fôlhas de café (Coffea arabica) a ultraestrutura característica e pràticamente desprovida do tipo de ornamentação encontrado nas fôlhas de couve.
Influência de cafés de gôsto rio em ligas com cafés de bebida mole
Authors: Castilho Antonio de , Gomes F. Pimentel , Pereira Luiz Sergio de Paiva , Moraes Roberto S. , Lourenço Sidival
Published: June 2012

Os autores estudam a influência do café Rio em ligas com cafés brasileiros de bebida Mole. Foram ensaiadas porcentagens crescentes de Café Rio: 0,0; 0,5; 1,0; 1,5; 2,0; 2,5; 3,0; 3,5; 4,0; 4,5; 5,0; 7,5; 10,0; 12,5; 15,0; 20,0; 25,0; 30,0; 35,0; 40,0; 50,0. Realizaram-se dois experimentos em blocos incompletos equilibrados, com t = 21 tratamentos (os mencionados acima), k = 3 parcelas por bloco, r = 10 repetições, b = 70 blocos, L = 1. Cada parcela era formada de 3 xícaras, de tipo padrão, sobre as quais cada degustador dava uma só opinião. Cada parcela era provada por 3 degustadores. Os dados coletados são, pois, 630 para cada ensaio (210 parcelas, 3 degustadores). Atribuia-se a cada parcela, para fins de análise estatística, a média das opiniões dos 3 degustadores. Os dois ensaios deram resultados bem concordantes, que levaram às seguintes conclusões: a) Faz-se necessária a transformação dos dados, pois as variâncias relativas aos diversos tratamentos são muito discrepantes. b) A transformação T = √ Y dá resultados satisfatórios. c) O café Rio prejudica sensivelmente a bebida do café Mole, para teores a partir de 2,0%. d) Para teores de 4,5% em diante a liga tem bebida Riada ou Rio. e) A regressão obtida não é estritamente linear, mas a linha reta da uma aproximação razoável. f) Consideradas as porcentagens de 0,0 a 10,0%,a equação de regressão para os dados transformados pela transformação T = √ Y é: T = 1,7045 - 0,127 X, onde X é a porcentagem de café Rio e T dá a bebida, na escala numérica adotada, transformada pela raíz quadrada. g) A equação de regressão para os tratamentos de 0,0 a 10,0% de cafe Rio é Y = 3,0997 - 0,3281 X, isto é, há uma queda de 0,3281 na escala numérica da bebida, para cada unidade de porcentagem de café Rio.
Absorção dos macronutrientes pelos capins colonião, gordura jaraguá, napier e pangola
Authors: Haag H.P. , Bose M.L.V. , Andrade R.G.
Published: June 2012

Para determinar a absorção de nitrogênio, fósforo, potássio, cálcio, magnésio e enxofre em 5 espécies de forragens, conduziu-se um ensaio em vasos ao ar livre. Cada 28 dias até aos 84 dias colhiam-se plantas para a determinação de pêso de matéria sêca, bem como para a análise quantitativa dos macronutrientes. Verificou-se que o máximo de crescimento foi atingido pelo capim napier seguido do colonião, jaraguá, gordura e pangola. O potássio e nitrogênio são absorvidos em maior quantidade do que o cálcio, fósforo, magnésio e enxôfre. As quantidades de nutrientes extraídos pelas plantas aos 84 dias de idade em g por kg de matéria sêca se acham ilustradas abaixo.
A determinação da água livre em substâncias puras
Authors: Catani R.A. , Alcarde J.C. , Furlani P.R.
Published: June 2012

O presente trabalho relata os dados obtidos sôbre a determinação da água livre em diversas substâncias puras pelo método baseado no uso da estufa comum a 100-105ºC (método clássico) e pelo método que usa 20 polegadas (ou 50 mm de mercúrio) de vácuo a 50°C. As substâncias empregadas foram cloreto de sódio, sulfato de cálcio dihidratado, ortofosfato monocálcico monohidratado, ortofosfato bicálcico dihidratado, ortofosfato monácido de amônio e uréia cristalizada. Os resultados obtidos permitem concluir que o método que usa estufa a vácuo a 50°C apresenta uma tendência de retirar apenas a água livre das substâncias estudadas. Por outro lado, o método clássico que emprega estufa comum a 100-105°C, além da água livre, retira também uma fração variável da água de hidratação ou de cristalização das substâncias que a contém.
Estudos sôbre a alimentação mineral do cafeeiro: XXI. efeito da adubação N, P, K e orgânica na composição mineral do grão e na qualidade da bebida. (2a. Nota)
Authors: Amorim H.V. de , Scoton L.C. , Castilho A. de , Gomes F. Pimentel , Malavolta E.
Published: June 2012

O efeito da adubaçao NPK e da matéria orgânica na composição mineral do grão e na qualidade da bebida (prova de xícara) foi estudado. Verificou-se que a adubação fosfatada e o uso da matéria orgânica não influiram nas características mencionadas. A adubação nitrogenada e potássica aumentou o teor dos elementos correspondentes no grão e prejudicou pouco mas, significativamente a qualidade da bebida. Esses dados devem ser encarados com cautela e tidos apenas como preliminares.
Variação na concentração e na quantidade de macro e micronutrientes no fruto do cafeeiro, durante o seu desenvolvimento
Authors: Catani R.A. , Pellegrino D. , Alcarde J.C. , Graner C.A.F.
Published: June 2012

O presente trabalho apresenta os dados obtidos sôbre a variação na concentração e na quantidade de macro e micronutrientes no fruto do cafeeiro em função do seu grau de desenvolvimento, através da análise de amostras colhidas mensalmente. A variedade de café usada foi bourbon vermelho, de 9 anos de idade, localizada num solo latosólico roxo, no município de Charqueada. Os resultados obtidos mostraram que os frutos exigem contìnuamente todos os macronutrientes, desde o início de sua formação até a maturação. Com relação aos micronutrientes, o boro, cobre, ferro e molibdênio também foram solicitados contìnuamente, ao passo que o manganês e o zinco deixaram de ser absorvidos nos dois últimos meses de seu ciclo formativo. A exigência quantitativa de micronutrientes obedeceu a seguinte ordem decrescente: ferro, manganês, cobre, boro, zinco e molibdênio.
Variabilidade de Stemphylium solari, Weber, agente causal de mancha foliar do tomateiro, no estado de São Paulo
Authors: Namekata Takao , Tokeshi Hasime
Published: June 2012

O presente trabalho trata do estudo da variabilidade do fungo, Stemphylium solani Weber, agente causal da Mancha Foliar do tomateiro (Lycopersicum esculentun Mill.), "Mancha de Estemfilium" que está se tornando cada vez mais importante em tôda área, onde se cultiva o tomateiro. Os autores isolaram 33 culturas de S. solani, de 12 municípios do Estado de São Paulo e estudaram suas capacidades de esporulação em meio de cultura. O modo de esporulação dos isolamentos variou bastante e reisolamentos e repicagens sucessivas mostraram que todos os isolamentos mantiveramas características culturais originais. Dois isolamentos (T-347 e T-419) comportaram-se de maneira bastante diferente dos demais isolamentos. Assim, êstes esporulavam espontânea e abundantemente em quaisquer meios, e nos testes de patogenicidade em tomateiro da variedade Santa Cruz, mostraram possuir elevada patogenicidade, que também confirmada estatìsticamente. Com base na capacidade de esporular em meios de cultura, patogenicidade em tomateiro suscetível e estabilidade das características culturais, os autores propuseram a classificação de S. solani, em 3 raças fisiológicas e discutem sua importância na interpretação de dados divergentes da literatura. Além disso, chamam a atenção para as culturas patogênicas capazes de esporular espontâneamente no meio de batata-dextroseagar e suas aplicações nos trabalhos de melhoramento do tomateiro.
Efeito de concentrações de macronutrientes N, P e K No aumento do espessamento da parede dos traqueídos Pinnus Elliottii (plantas em vasos)
Authors: Santos C.F. Oliveira , Malavolta E. , Haag H.P.
Published: June 2012

Neste trabalho os autores apresentam os resultados dos efeitos dos níveis de N, P e K no aumento do comprimento e da espessura da parede dos traqueídos de Pinnus elliottii. A análise estatística mostra que alto nível de N parece indicar uma diminuição no comprimento e na espessura dos traqueídos, enquanto que os efeitos do P e K não se mostram bem definidos, provàvelmente por se tratar de material muito jovem, com apenas dois anos de idade, sob efeito dos tratamentos.
II - Ocorrência das domácias nas angiospermas
Authors: Barros Myrthes A. Adamoli de
Published: June 2012

Continuando as observações nas folhas de plantas de nossa riquíssima flora à procura de domácias, examinamos as folhas de cerca de 129 exemplares pertencentes a 49 famílias. Destas especies apenas 14 dentre 8 familias revelaram essas interessantes estruturas. As domácias foram registradas nas fôlhas de plantas de pequeno e grande porte, assim como trepadeiras. As folhas herborizadas, foram examinadas em ambas as faces, na axila das nervuras e também na sua junção com o pecíolo. Relacionamos, por ordem alfabética, as famílias cujas espécies apresentaram domácias, assim como os nomes das plantas, o tipo e localização da domácia na folha, etc., usando sempre a classificação de domácias proposta por CHEVALIER & CHESNAIS (1941). Os tipos de domácias encontrados distribuem-se entre as famílias da seguinte maneira: a) Domacias em "tufo de pêlos" - encontradas em plantas das seguintes famílias: Bignoniaceae, Compositae, Convolvulaceae, Leguminosae, Moraceae, Solanaceae, Proteaceae e Oleaceae. b) Domacias em "bolsas" - registradas na família Solanaceae.
Mineralogia da fração argila de perfis de solos da série Ibitiruna
Authors: Demattê J.L.I. , Mendes A.C. Teixeira , Kinjo T.
Published: June 2012

O presente trabalho teve por finalidade o estudo minera lógico, da fração argila, da série Ibitiruna (RANZANI et al. 9), pertencente a unidade de mapeamento Podzólico Vermelho Amarelo - variação Laras (COMISSÃO DE SOLOS 1). Foram coletados três perfis de solos, pertencente a série Ibitiruna, designados por perfis P1, P2 e P3. As amostras dos horizontes foram colhidas a partir da superfície do solo até a rocha. A fração argila foi separada por sedimentação, sendo posteriormente, dividida em duas subfrações (centrifugação): 2 a 0,2 mícron e menor que 0,2 mícron, argila grossa e fina respectivamente. O material obtido nestas duas frações, sofreu determinações químicas (capacidade de troca de cátions) e determinações de raio-X (obtenção de difratogramas, com o auxílio do contador Geiger, e filmes, pelo método do pó). Através dêstes resultados, foi efetuado o reconhecimento dos minerais de argila assim como estimativa semiquantitativa. A análise mineralógica das frações argila grossa e fina, referentes à natureza e à quantidade dos minerais de argila indica o seguinte: a caolinita é o mineral dominante nas duas frações argila, com teores sempre acima de 40%; a montmorilonita e os minerais do grupo de 14 Anormalmente ocorrem com valôres inferiores a 10%.
Emprêgo de coluna de resina trocadora de cátions na separação de cátions e ânions de extrato de material vegetal
Authors: Glória N.A. da , Vitti G.C.
Published: June 2012

O presente trabalho descreve a técnica de separação de cátions e ânions de solução pura, contendo os principais íons que ocorrem em material vegetal, mediante o emprego de coluna de resina trocadora de cátions Dowex 50 - X8. Foram estudados o efeito do pH na retenção dos cátions, a eluição destes e a sua recuperação, a lavagem da coluna de resina e a recuperação dos ânions. Mediante os resultados obtidos, foi possível estabelecer condições para o emprego da citada técnica na separação de cátions e ânions em extratos provenientes de material vegetal.
Nutrição mineral de hortaliças IV absorção de nutrientes pela cultura da beringela
Authors: Haag H.P. , Homa P.
Published: June 2012

Plantas de beringela da var. Hibrida F. Piracicaba nº 100 foram cultivadas em vasos contendo sílica e irrigados com solução nutritiva completa. Quando as plantas atingiram 36 dias de idade da germinação, foram colhidas amostras de 10 em 10 dias até aos 126 dias para determinação do pêso da matéria fresca e sêca, assim como, análises químicas quantitativas para N, P, K, Ca, Mg e S. 0 crescimento e a absorção de nutrientes é lenta até aos 56 dias intensificando-se com o crescimento da planta. Uma população de 20.000 plantas correspondentes a um ha absorvem 88,8 kg de nitrogênio, 9,8 kg de fósforo, 142 kg de potássio, 43,1 kg de cálcio, 13,4 kg de magnésio e 5,4 kg de enxofre.
A determinação de enxofre em plantas pelo método quelatométrico do BDTA
Authors: GLória N.A. , Vitti G.C.
Published: June 2012

Neste trabalho são relatados estudos a respeito do método quelatométrico de determinação de sulfato, baseado na titulação do bário residual com solução de EDTA, após a precipitação do citado ânion na forma de sulfato de bário. Foram estudados aspectos relativos ao emprego de diferentes indicadores e passou-se a preconizar o uso de solução de púrpura de ftaleína a 0,2%. São descritos experimentos relativos à determinação de sulfato em soluções puras, observando-se o período de precipitação e a influência de diversos ânions. Finalmente, tendo por base os dados obtidos, é preconizada urna marcha analítica para determinação de enxôfre total e enxôfre-sulfato em material vegetal. Os resultados obtidos quando se empregou a técnica proposta na determinação de sulfato em materiais vegetais, foram comparados com aquêles fornecidos pelo método gravimétrico, baseado na pe-sagem do sulfato de bário.
A determinação direta do nitrogênio nítrico, amoniacal e amídico (uréia) em fertilizantes
Authors: Catani R.A. , Bataglia O.C.
Published: June 2012

O presente trabalho tem por objetivo o estudo da determinação direta de diversas formas de nitrogênio (nítrico, amoniacal e amídico) em fertilizantes simples e em misturas. Constatada a presença das três formas citadas de nitrogênio, o extrato aquoso de 250 ml, obtido pelo tratamento de 2,5000 g da amostra, pode ser destinado às mencionadas determinações. Uma alíquota de 50 ml é transferida para uma coluna de resina de troca aniônica DOWEX-1-X8, que, convenientemente preparada, retém o ânion nitrato(NO-3), separando-o de outras formas. Em seguida, determina-se o nitrogênio nítrico na solução obtida pela eluição da coluna com solução de NaCl a 20%. O nitrogênio amoniacal pode ser determinado em uma alíquota do extrato aquoso original ou na solução que passa através da coluna de resina para a separação do nitrato. O nitrogênio amídico (uréia) é determinado numa alíquota do extrato original pelo método da urease. Os métodos e técnicas preconizados foram préviamente estudados, através de determinações em soluções contendo substâncias puras (nitrato de sódio p.a., sulfato de amônio p.a. e uréia p.a.). Numa segunda fase, procedeu-se a aplicação dos mencionados métodos e técnicas na determinação do nitrogênio em misturas de fertilizantes preparadas em laboratório, em fertilizantes comerciais simples e em misturas também comerciais. Os resultados obtidos indicam que os métodos e técnicas recomendados permitem a determinação direta e relativamente rápida do nitrogênio nítrico, amoniacal e amídico (uréia) em fertilizantes.
A determinação do boro em plantas pelo método colorimétrico da curcumina
Authors: Alcarde J.C.
Published: June 2012

O presente trabalho relata os estudos desenvolvidos sobre a determinação do boro em plantas através do método da curcumina, que se fundamenta na formação do complexo rosocianina em meio acético- sulfúrico. Nesse método a reação de formação da rosocianina é desenvolvida em meio líquido e à temperatura ambiente, não necessitando, portanto, do controle da temperatura a 55±3°C, conforme é exigido pelo método comum, cujo complexo formado é principalmente rubrocurcumina. Uma alíquota do extrato do vegetal é tornada alcalina pela adição de solução de NaOH e sêca em banho-maria. Sobre o resíduo obtido adicionam-se a solução acética de curcumina a 0,125% e a solução de ácido sulfúrico -ácido acético ( 1 + 1 ). A reação completa-se em 15 minutos. No estudo da aplicação do método em plantas, diversos aspectos foram abordados, como: interferentes e sua eliminação, a solubilização do boro contido nas amostras incineradas, a contaminação do extrato de vegetal pelo papel de filtro, como conseqüência da filtração a que deve ser submetido, e a precisão e a exatidão do referido método. Os resultados obtidos permitiram concluir que, dentre os elementos normalmente encontrados nas cinzas vegetais, os que interferem no citado método sao o cálcio (Ca2+), o magnésio (Mg2+), o ferro (Fe3+), o manganês (Mn2+) e o cobalto (Co2+). Esses elementos foram eliminados do extrato de planta, passando-o através de resina catiônica. O método, conforme é preconizado, pode ser considerado eficiente na determinação do boro em plantas, pois, mostrou possuir precisão e exatidão satisfatórios, aliadas à sua alta sensibilidade, permitindo determinar desde 2 ppm de boro em plantas, dentro do seu intervalo de menor erro.
A determinação do nitrato em extratos de planta e de solos pelo método de absorção no ultra-violeta
Authors: Bittencourt V.C.
Published: June 2012

Êste trabalho apresenta dados referentes à determinação do íon nitrato em extratos aquosos de vegetais e em extratos de solos obtidos com solução de ácido sulfúrico 0,01 N. Em ambos os casos, a matéria orgânica presente mostrou forte interferência, impedindo totalmente a determinação do ânion nas soluções, sem qualquer tratamento prévio. Os extratos aquosos de vegetais foram tratados com peróxido de hidrogênio em presença de carbonato de magnésio, para a eliminação de quantidades consideráveis de materia orgânica. Os extratos de solos que apresentam quantidades menores do interferente, foram analisados através de uma técnica diferente. Uma alíquota da amostra, tratada com sulfato de hidrazina para a eliminação total do nitrato, foi usada como prova em branco, na correção das absorbâncias. Após o tratamento inicial, as soluções foram tratadas com os ácidos sulfúrico, perclórico e clorídrico para a formação do cloreto de nitrosilo, o qual mostra um máximo de absorção em 230 milimicrons.
Extração e determinação do íon amônio do solo
Authors: Catani R.A. , Bittencourt V.C. de , Cangiani A.M.
Published: June 2012

Este trabalho descreve a determinação do íon amônio em solos, pelo método colorimétrico baseado no reativo de Nessler. Foram estudados diversos aspectos, como o espectro de absorção do composto colorido e do reativo de Nessler, a influência do tempo de repouso e da temperatura sobre o desenvolvimento da côr e a interferência de alguns íons que normalmente se encontram nos extratos de solos. A determinação do íon amônio foi conduzida em extratos de solos obtidos com solução de KC1 1 N e destilados, para evitar a interferência do íon manganês-II, que forma um precipitado com o reativo de Nessler. Os resultados obtidos pelo método colorimétrico foram comparados com os determinados pelo método titrimétrico.