4,136 research outputs found
A computationally efficient method for calculating the maximum conductance of disordered networks: Application to 1-dimensional conductors
Random networks of carbon nanotubes and metallic nanowires have shown to be
very useful in the production of transparent, conducting films. The electronic
transport on the film depends considerably on the network properties, and on
the inter-wire coupling. Here we present a simple, computationally efficient
method for the calculation of conductance on random nanostructured networks.
The method is implemented on metallic nanowire networks, which are described
within a single-orbital tight binding Hamiltonian, and the conductance is
calculated with the Kubo formula. We show how the network conductance depends
on the average number of connections per wire, and on the number of wires
connected to the electrodes. We also show the effect of the inter-/intra-wire
hopping ratio on the conductance through the network. Furthermore, we argue
that this type of calculation is easily extendable to account for the upper
conductivity of realistic films spanned by tunneling networks. When compared to
experimental measurements, this quantity provides a clear indication of how
much room is available for improving the film conductivity.Comment: 7 pages, 5 figure
Can the distributional impacts of macroeconomic shocks be predicted? A comparison of the performance of macro-micro models with historical data for Brazil
What was the impact of Brazil's 1998-99 currency crisis-which resulted in a change of exchange rate regime and a large real devaluation-on the occupational structure of the labor force and the distribution of incomes? Would it have been possible to predict such effects ahead of the crisis? The authors present an integrated macro-micro model of the Brazilian economy in 1998. The model consists of an applied general equilibrium macroeconometric component, connected through a set of linkage aggregate variables to a microeconomic model of household incomes. The authors use this framework to predict the employment and distributional consequences of the 1999 Brazilian currency crisis, based on 1998 household survey data. They then test the predictive performance of the model by comparing its simulated results with the actual household survey data observed in 1999. In addition to the fully integrated macro-micro model, the authors also test the performances of the microeconometric model on its own, and of a"representative household groups"approach. They find that the integrated macro-micro econometric model, while still inaccurate on many dimensions, can actually predict the broad pattern of the incidence of changes in household incomes across the distribution reasonably well, and much better than the alternative approaches. The authors conclude that further experimentation with these tools might be of considerable potential usefulness to policymakers.Labor Policies,Payment Systems&Infrastructure,Economic Theory&Research,Banks&Banking Reform,Environmental Economics&Policies,Economic Theory&Research,Environmental Economics&Policies,Macroeconomic Management,Inequality,Economic Stabilization
Hopf and zip bifurcation in a specific (n+1)-dimensional competitive system
In this work we study the occurrence of Andronov-Hopf and zip bifurcation in a concrete
(n + 1)-dimensional predator-prey system modelling the competition among n species of
predators for one species of prey. This is a generalization of results by Farkas (1984
Integrable theories in any dimension and homogenous spaces
We construct local zero curvature representations for non-linear sigma models
on homogeneous spaces, defined on a space-time of any dimension, following a
recently proposed approach to integrable theories in dimensions higher than
two. We present some sufficient conditions for the existence of integrable
submodels possessing an infinite number of local conservation laws. Examples
involving symmetric spaces and group manifolds are given. The models are
discussed in detail.Comment: LaTeX, 35 page
A Brief View of Molecular Modeling Approaches to P2 Receptors
Purinergic receptors are a class of receptors distributed into two groups, P1 and P2. P1 receptors are activated by nucleosides, like adenosine, while nucleotides active P2 receptors. In turn, P2 receptors comprise two families, metabotropic P2Y and ionotropic P2X. P2Y receptors consist in eight members, namely, P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13, and P2Y14, described in mammals, while P2X includes seven members, numbered P2X1 to P2X7. These receptors have been described as expressed in practically all cells studied to date. In this context, P2 receptors are suggested as participating in certain diseases. The general approach applied in the discovery of new drugs is expensive and lengthy. Alternatively, in the last 20 years, molecular modeling has emerged as an exciting tool for the design of new drugs, in less time and at low costs. These tools allow for in silico testing of thousands of molecules against a target protein, as well as toxicity, absorption, distribution, metabolism, and constant affinity predictions of a given interaction. Thus, molecular modeling algorithms emerge as an increasingly important tool for the design of drugs targeting purinergic receptors as therapeutic targets of many diseases, including cancer, pain, inflammation, cardiovascular, and endocrine conditions
ATZ (3‐amino‐1,2,4‐triazole) injected into the fourth cerebral ventricle influences the Bezold–Jarisch reflex in conscious rats
OBJECTIVES: Many studies have investigated the importance of oxidative stress on the cardiovascular system. In this study we evaluated the effects of central catalase inhibition on cardiopulmonary reflex in conscious Wistar rats. METHODS: Male Wistar rats were implanted with a stainless steel guide cannula in the fourth cerebral ventricle. The femoral artery and vein were cannulated for mean arterial pressure and heart rate measurement and for drug infusion, respectively. After basal mean arterial pressure and heart rate recordings, the cardiopulmonary reflex was tested with a dose of phenylbiguanide (PBG, 8 μg/kg, bolus). Cardiopulmonary reflex was evaluated before and μl15 minutes after 1.0 μl 3-amino-1,2,4-triazole (ATZ, 0.01g/100μl)0.01 g/100 μl) injection into the fourth cerebral ventricle. Vehicle treatment did not change cardiopulmonary reflex responses. RESULTS: Central ATZ significantly increased hypotensive responses without influencing the bradycardic reflex. CONCLUSION: ATZ injected into the fourth cerebral ventricle increases sympathetic inhibition but does not change the parasympathetic component of the cardiopulmonary reflex in conscious Wistar rats
WHO ARE THE STUDENTS OF THE DENTISTRY PROGRAM AT ULBRA IN CANOAS, RS, WHAT THEY THINK AND WHAT THEY EXPECT OF THE JOB MARKET: A CROSS-SECTIONAL STUDY
Dentistry programs should prepare professionals with a generalist profile, having biological, scientific, technical, social and humanistic training. They should be trained for the reality of the job market and to practice Dentistry in both public and private settings, in order to provide leadership in the community in which they are placed. Objective: This study aims to analyze the socio-demographic profile, satisfaction with the program, self-evaluation of academic performance and expectations of the job market of students entering and exiting the Dentistry program of ULBRA/Canoas. Methodology: This is an observational, cross-sectional study conducted using a questionnaire with different questions for students entering and exiting the program in 2015. A questionnaire was developed with both open and closed objective, multiple-choice questions. It was given to 71 (86.5%) students enrolled in the program. Results: Most of the subjects are female, single, childless and between the ages of 17 and 36 years. Most chose Dentistry as a profession because they always liked or were interested in the health field. It was observed that the exiting students worked more in the areas of General Dentistry (90.4%) and Periodontics (77.0%) during their academic time, and intended to work in private practice (49.0%) and in the Unified Health System (65.0%). Conclusion: It was concluded that the profile of the entering and the exiting students is diverse, also that the students perceive that the greatest difficulty in the practice of Dentistry is the insertion and saturation of the job market
The active mathematics project at ISCAP
This paper summarizes a project that is contributing to a change in the way of teaching and learning Mathematics.
Mathematics is a subject of the Accounting and Administration course. In this subject we teach: Functions and Algebra. The aim is that the students understand the basic concepts
and is able to apply them in other issues, when possible, establishing a bridge between the
issues that they have studied and their application in Accounting.
As from this year, the Accounting course falls under in Bologna Process. The teacher and
the student roles have changed. The time for theoretical and practical classes has been
reduced, so it was necessary to modify the way of teaching and learning.
In the theoretical classes we use systems of multimedia projection to present the concepts,
and in the practical classes we solve exercises.
To supplement our theoretical and practical classes we have developed an active
mathematics project called MatActiva based on the Moodle platform offered by PAOL -
Projecto de Apoio Online (Online Support Project). In the last versions of Moodle, it is
possible use the TeX language to create math questions. Using this tool we created a set of
interactive materials.
With the creation of this new project we wanted to take advantage already obtained results
with the previous experiences, giving to the students opportunities to complement their
study in Mathematics.
One of the great objectives is to motivate students, encourage them to overcome theirs
difficulties through an auto-study, giving them more confidence and the opportunity to
seeing others perspectives of the mathematics subjects.
In the MatActiva project the students have a big collection of information about the way of
the subject works, which includes the objectives, the program, recommended bibliography,
evaluation method and summaries. It works as material support for the practical and
theoretical classes, the slides of the theoretical classes are available, the sheets with
exercises for the students to do in the classroom and complementary exercises, as well as
the exams of previous years. Students can also do diagnostic tests and evaluation tests
online.
Our approach is a reflexive one, based on the professional experience of the teachers that
explore and incorporate new tools of Moodle with their students and coordinate the project
MatActiva
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