556 research outputs found
Chromoelectric fields and quarkonium-hadron interactions at high energies
We develop a simple model to study the heavy quarkonium-hadron cross section
in the high energy limit. The hadron is represented by an external electric
color field (capacitor) and the heavy quarkonium is represented by a small
color dipole. Using high energy approximations we compute the relevant cross
sections, which are then compared with results obtained with other methods. Our
calculations are presented in a pedagogical way accessible to undergraduate
students.Comment: To appear in Physical Review C, 24 pages, 10 eps figure
Uma adapta??o da Cifra de Hill para estudo de matrizes.
Programa de P?s-Gradua??o em Matem?tica em Rede Nacional. Departamento de Matem?tica, Instituto de Ci?ncias Exatas e Biol?gicas, Universidade Federal de Ouro Preto.Neste trabalho ser?o apresentados alguns dos principais resultados matem?ticos a respeito
de Aritm?tica Modular, dando ?nfase ?s rela??es de equival?ncia e classes residuais. ? feito
tamb?m um estudo sobre matrizes e suas propriedades operacionais; a fun??o determinante
? constru?da e apresentada como instrumento para o c?lculo de matrizes inversas. Tais temas
s?o abordados com o intuito de fundamentar os processos matem?ticos aplicados para funcionamento
da Cifra de Hill. Essa cifra ? um dos m?todos de criptografia apresentados neste texto
e ao qual daremos destaque. Para finalizar, foi desenvolvida uma atividade voltada para turmas
do Ensino M?dio e baseada na Cifra de Hill, cujo principal objetivo ? despertar o interesse dos
alunos para o estudo de matrizes.In this paper, some of the main mathematical results will be presented about Modular Arithmetic,
emphasizing the relations of equivalence and residue classes. Besides, a study on matrices
and their operational properties; the determinant function is constructed and presented as an
instrument for the calculation of inverse matrices. These themes are approached in order to
base the mathematical processes applied to the operation of the Hill Cipher. This cipher is one
of the cryptographic methods presented in this text and we will highlight it. To conclude, an
activity was developed, focused on high school classes and based on Hill Cipher, which main
objective is to arouse students? interest in studying matrices
Uma adapta??o da Cifra de Hill para estudo de matrizes.
Neste artigo ser?o apresentados alguns dos principais resultados matem?ticos a respeito de
Aritm?tica Modular, dando ?nfase ?s rela??es de equival?ncia e classes residuais, al?m de alguns fatos sobre matrizes em Zp. Tais temas s?o abordados com o intuito de fundamentar os processos matem?ticos aplicados para funcionamento da Cifra de Hill, que ? um modelo de criptografia utilizado como inspira??o para o desenvolvimento de uma atividade voltada para turmas de Ensino M?dio
Identification and analysis of errors in the preparation of drugs in a pediatric hospital unit
Este estudo objetivou identificar e analisar os erros no preparo de medicamentos em unidade pedi?trica de uma institui??o hospitalar. Trata-se de estudo descritivo, realizado com quatro profissionais respons?veis pelo preparo dos medicamentos de um hospital do interior do Estado de Minas Gerais, que foram submetidos ? t?cnica de observa??o estruturante e formul?rio. Utilizou-se a an?lise descritiva junto aos dados. Como resultados, destacam-se a inexist?ncia de diretrizes para o preparo de medicamentos, presen?a de interrup??es durante o processo, n?o utiliza??o das t?cnicas de lavagem das m?os e de desinfec??o de frascos e ampolas. Faz-se necess?ria a conscientiza??o dos profissionais para a ocorr?ncia e consequ?ncias dos erros cometidos pela equipe, como forma de est?mulo para a preven??o dos mesmos, atrav?s de pr?ticas seguras e efetivas, a fim de ampliar a qualidade da assist?ncia.Funda??o de Amparo ? Pesquisa do Estado de Minas Gerais (FAPEMIG)Empresa de Pesquisa Agropecu?ria de Minas Gerais (EPAMIG)Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)This study aimed to identify and analyze errors in the preparation of medicines in the pediatric unit of a hospital. This descriptive study was performed with 04 professionals responsible for preparation of medicines developed in a hospital in the interior of Minas Gerais, Brasil, that were submitted to the technique of structural observation and formulary. A descriptive analysis of the data was performed. The results highlight the lack of guidelines for the preparation of drugs, presence of interruptions during the process failure of utilization of recommended hand washing techniques, and disinfection of bottles and vials. It is necessary to make professionals aware of the occurrence and consequences of the main mistakes made by the team, as a stimulus for prevention through safe and effective practices to improve the quality of care
Entanglement study of the 1D Ising model with Added Dzyaloshinsky-Moriya interaction
We have studied occurrence of quantum phase transition in the one-dimensional
spin-1/2 Ising model with added Dzyaloshinsky-Moriya (DM) interaction from bi-
partite and multi-partite entanglement point of view. Using exact numerical
solutions, we are able to study such systems up to 24 qubits. The minimum of
the entanglement ratio R \tau 2/\tau 1 < 1, as a novel estimator of
QPT, has been used to detect QPT and our calculations have shown that its
minimum took place at the critical point. We have also shown both the
global-entanglement (GE) and multipartite entanglement (ME) are maximal at the
critical point for the Ising chain with added DM interaction. Using matrix
product state approach, we have calculated the tangle and concurrence of the
model and it is able to capture and confirm our numerical experiment result.
Lack of inversion symmetry in the presence of DM interaction stimulated us to
study entanglement of three qubits in symmetric and antisymmetric way which
brings some surprising results.Comment: 18 pages, 9 figures, submitte
Impact of extreme weather events frequency and intensity in shaping phytoplankton communities
Lake habitats and communities can often be correlated with general morphometric and geographic
characteristics such as depth, latitude, altitude, or watershed area. Further, communities are typically
correlated with average environmental conditions such as seasonal temperature and nutrient levels. The
frequency and intensity of extreme weather events (rain and wind) are typically not encompassed by average
environmental descriptors, yet, can modify the physical habitats of lakes, significantly influencing
phytoplankton growth and survival. We tested the hypothesis that lakes with a higher frequency and intensity
of extreme weather events have a functionally different phytoplankton assemblage from lakes with a lower
frequency of extreme weather events. We compiled long-term (mean = 20±13 years, range 0.6-44 years)
phytoplankton datasets for 22 lakes across a wide gradient of altitude, latitude, depth, and trophic state. We
classified the phytoplankton genera into morpho-functional groups and C-S-R strategists, and compared
among lake phytoplankton assemblages’ characteristics across the gradient of wind and rain conditions
experienced by the lakes. We discuss how the frequency of extreme weather events can affect phytoplankton
functional groups, the dominance of differing life history strategies and ultimately community structure. The
frequency and intensity of extreme events is expected to increase with climate change, with the potential to
drive shifts in phytoplankton composition
Separability and entanglement in 2x3xN composite quantum systems
The separability and entanglement of quantum mixed states in \Cb^2 \otimes
\Cb^3 \otimes \Cb^N composite quantum systems are investigated. It is shown
that all quantum states with positive partial transposes and rank
are separable.Comment: Latex, 15 page
A global dataset on weather, lake physics, and phytoplankton dynamics
We compiled data from over 30 lakes across the globe to address how storms influence thermal structure
and phytoplankton community dynamics mediated by lake conditions and functional traits. In addition to
(generally) fortnightly phytoplankton samples (mean ± SD temporal coverage across all lakes = 20 ± 13 years),
the dataset includes limnological variables from standard long-term monitoring programs (24 ± 15 years
coverage), daily weather observations (16 ± 10 years coverage) and, when available, high-frequency lake
water temperature and water chemistry profiles (12 ± 7 years coverage). All data have been standardized to
similar formats and include complete metadata. We used the dataset to develop an R-package
(“algaeClassify”), which assigns phytoplankton genus/species information to multiple functional trait groups,
and here we provide a summary of ongoing research using the dataset to investigate: 1) the influence of storm
events on seasonal phytoplankton succession, 2) the impact of storms on lake thermal structure, and 3)
whether lake phytoplankton communities are shaped by long-term patterns in disturbance frequency and
intensity. We give an overview on how to access these data, and we further highlight the opportunities the
dataset provides for asking both basic and applied questions in limnology, ecology, climate change, and lake
management
Decision Making with Asymmetric Information
Every day individuals make numerous choices. What is important for making the
right choice is that individuals have good information about the consequences of the
different alternatives. However, investigating the full consequences of the different
alternatives is complicated and costly. Consequently, individuals sometimes do not
possess all relevant information to take a decision.
This thesis discusses models in which an agent decides whether or not to perform
a task on behalf of the principal. A key element in the models we consider is
incomplete and asymmetric information. Broadly, the thesis can be split up into
two parts. The first part of the thesis deals with models in which the principal is
better informed than the agent. The agent has to decide whether or not to perform
a task, but lacks information about his ability. We analyze how the agent makes
a self-assessment of his ability, based on appraisals of others (the principal) and
experience. Based on this self-assessment the agent takes a decision. The second
part of the thesis deals with models in which the agent is better informed than the
principal. On behalf of the principal the agent takes a decision about a project.
Sometimes agents do not act in the interest of the principal. We analyze how the
principal can use retention contracts to discipline the agent.
In the remainder of the Introduction we discuss the two parts of the thesis and
we provide an overview of the chapters of this thesis
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