795 research outputs found
On fiber diameters of continuous maps
We present a surprisingly short proof that for any continuous map , if , then there exists no bound on
the diameter of fibers of . Moreover, we show that when , the union of
small fibers of is bounded; when , the union of small fibers need not
be bounded. Applications to data analysis are considered.Comment: 6 pages, 2 figure
Assessment of the Effectiveness of Risk Management Practices in the Performance of IT Projects
This study assessed the effectiveness of risk management practices in the performance of IT projects. This study was guided by Project Management Theory. The study employed a mixed research approach, a mixed research approach and descriptive research design. The study was conducted at the Tanzania Revenues Authority Head Office in Dar es Salaam, the targeted population of this study is 200 and the sample size was 133 obtained suing simple random sampling techniques and purposive sampling techniques. in this study data was analysed using quantitative and qualitative techniques. The findings show that management practices are very essential in the implementation of the IT projects. It was also shown that effective project implementation depends much on the effective risk management practice because it is through them that risk can be mitigated for the sustainability of the IT projects. moreover, the results obtained through correlation analysis shows that Risk Assessment Practices (RAP) correlated (r (125)> .568, P< .000), Risk Response Practices (RRP) correlated (r (125)> 452, P < .000), Risk Response Practice (RRP) and the performance of IT Projects (PIP). Lastly Monitoring and Control Process (MCP) had a correlation of (r (125)> 652, P < .000. The results of this study concluded that there is a positive and significance relationship between risk management practices and the performance of IT projects. Despite of these supportive findings this study recommended for the proactive management of project risk because IT project implementation is subject to the limitation challenges and risks, thus through proactive management of project risk a comprehensive assessment of risk and preparation of a suitable management plan can be activated. The study recommended further research be conducted on the assessment of the effectiveness of implementation approaches toward project sustainability
Dynamical mean field solution of the Bose-Hubbard model
We present the effective action and self-consistency equations for the
bosonic dynamical mean field (B-DMFT) approximation to the bosonic Hubbard
model and show that it provides remarkably accurate phase diagrams and
correlation functions. To solve the bosonic dynamical mean field equations we
use a continuous-time Monte Carlo method for bosonic impurity models based on a
diagrammatic expansion in the hybridization and condensate coupling. This
method is readily generalized to bosonic mixtures, spinful bosons, and
Bose-Fermi mixtures.Comment: 10 pages, 3 figures. includes supplementary materia
A non inflationary model with scale invariant cosmological perturbations
We show that a contracting universe which bounces due to quantum cosmological
effects and connects to the hot big-bang expansion phase, can produce an almost
scale invariant spectrum of perturbations provided the perturbations are
produced during an almost matter dominated era in the contraction phase. This
is achieved using Bohmian solutions of the canonical Wheeler-de Witt equation,
thus treating both the background and the perturbations in a fully quantum
manner. We find a very slightly blue spectrum (). Taking
into account the spectral index constraint as well as the CMB normalization
measure yields an equation of state that should be less than , implying , and
that the characteristic size of the Universe at the bounce is , a region where one expects that the Wheeler-DeWitt
equation should be valid without being spoiled by string or loop quantum
gravity effects.Comment: 9 pages, 4 figure
Tensor Perturbations in Quantum Cosmological Backgrounds
In the description of the dynamics of tensor perturbations on a homogeneous
and isotropic background cosmological model, it is well known that a simple
Hamiltonian can be obtained if one assumes that the background metric satisfies
Einstein classical field equations. This makes it possible to analyze the
quantum evolution of the perturbations since their dynamics depends only on
this classical background. In this paper, we show that this simple Hamiltonian
can also be obtained from the Einstein-Hilbert lagrangian without making use of
any assumption about the dynamics of the background metric. In particular, it
can be used in situations where the background metric is also quantized, hence
providing a substantial simplification over the direct approach originally
developed by Halliwell and Hawking.Comment: 24 pages, JHEP forma
A Method for Cost-Effective and Rapid Characterization of Engineered T7-based Transcription Factors by Cell-Free Protein Synthesis Reveals Insights into the Regulation of T7 RNA Polymerase-Driven Expression
The T7 bacteriophage RNA polymerase (T7 RNAP) serves as a model for understanding RNA synthesis, as a tool for protein expression, and as an actuator for synthetic gene circuit design in bacterial cells and cell-free extract. T7 RNAP is an attractive tool for orthogonal protein expression in bacteria owing to its compact single subunit structure and orthogonal promoter specificity. Understanding the mechanisms underlying T7 RNAP regulation is important to the design of engineered T7-based transcription factors, which can be used in gene circuit design. To explore regulatory mechanisms for T7 RNAP-driven expression, we developed a rapid and cost-effective method to characterize engineered T7-based transcription factors using cell-free protein synthesis and an acoustic liquid handler. Using this method, we investigated the effects of the tetracycline operator's proximity to the T7 promoter on the regulation of T7 RNAP-driven expression. Our results reveal a mechanism for regulation that functions by interfering with the transition of T7 RNAP from initiation to elongation and validates the use of the method described here to engineer future T7-based transcription factors
22q11.2 deletion syndrome
22q11.2 deletion syndrome (22q11.2DS) is the most common chromosomal microdeletion disorder, estimated to result mainly from de novo non-homologous meiotic recombination events occurring in approximately 1 in every 1,000 fetuses. The first description in the English language of the constellation of findings now known to be due to this chromosomal difference was made in the 1960s in children with DiGeorge syndrome, who presented with the clinical triad of immunodeficiency, hypoparathyroidism and congenital heart disease. The syndrome is now known to have a heterogeneous presentation that includes multiple additional congenital anomalies and later-onset conditions, such as palatal, gastrointestinal and renal abnormalities, autoimmune disease, variable cognitive delays, behavioural phenotypes and psychiatric illness - all far extending the original description of DiGeorge syndrome. Management requires a multidisciplinary approach involving paediatrics, general medicine, surgery, psychiatry, psychology, interventional therapies (physical, occupational, speech, language and behavioural) and genetic counselling. Although common, lack of recognition of the condition and/or lack of familiarity with genetic testing methods, together with the wide variability of clinical presentation, delays diagnosis. Early diagnosis, preferably prenatally or neonatally, could improve outcomes, thus stressing the importance of universal screening. Equally important, 22q11.2DS has become a model for understanding rare and frequent congenital anomalies, medical conditions, psychiatric and developmental disorders, and may provide a platform to better understand these disorders while affording opportunities for translational strategies across the lifespan for both patients with 22q11.2DS and those with these associated features in the general population
Dynamical mean-field theory for bosons
We discuss the recently developed bosonic dynamical mean-field (B-DMFT)
framework, which maps a bosonic lattice model onto the selfconsistent solution
of a bosonic impurity model with coupling to a reservoir of normal and
condensed bosons. The effective impurity action is derived in several ways: (i)
as an approximation to the kinetic energy functional of the lattice problem,
(ii) using a cavity approach, and (iii) by using an effective medium approach
based on adding a one-loop correction to the selfconsistently defined
condensate. To solve the impurity problem, we use a continuous-time Monte Carlo
algorithm based on a sampling of a perturbation expansion in the hybridization
functions and the condensate wave function. As applications of the formalism we
present finite temperature B-DMFT phase diagrams for the bosonic Hubbard model
on a 3d cubic and 2d square lattice, the condensate order parameter as a
function of chemical potential, critical exponents for the condensate, the
approach to the weakly interacting Bose gas regime for weak repulsions, and the
kinetic energy as a function of temperature.Comment: 26 pages, 19 figure
Spontaneous self-affirmation is associated with psychological well-being: evidence from a US national adult survey sample
Emerging evidence suggests that individuals spontaneously self-affirm, by reflecting on values and strengths, in response to daily threats. We examined the prevalence and demographic and well-being correlates of spontaneous self-affirmation in the general population. Participants (n = 3185) completed the cross-sectional, nationally representative 2013 Health Information National Trends Survey (HINTS 4, Cycle 3), and answered questions about spontaneous self-affirmation, demographic factors, well-being, and affect. The majority of the population reported spontaneously self-affirming. Black and Hispanic respondents reported engaging in more spontaneous self-affirmation. Engaging in spontaneous self-affirmation was related to greater happiness, hopefulness, optimism, subjective health, and personal health efficacy, and less anger and sadness
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