2,165 research outputs found
The characteristics of plutonic rocks in various climatic zones as shown on multiband satellite imagery
Imperial Users onl
Experimental implementation of a four-player quantum game
Game theory is central to the understanding of competitive interactions
arising in many fields, from the social and physical sciences to economics.
Recently, as the definition of information is generalized to include entangled
quantum systems, quantum game theory has emerged as a framework for
understanding the competitive flow of quantum information. Up till now only
two-player quantum games have been demonstrated. Here we report the first
experiment that implements a four-player quantum Minority game over tunable
four-partite entangled states encoded in the polarization of single photons.
Experimental application of appropriate quantum player strategies give
equilibrium payoff values well above those achievable in the classical game.
These results are in excellent quantitative agreement with our theoretical
analysis of the symmetric Pareto optimal strategies. Our result demonstrate for
the first time how non-trivial equilibria can arise in a competitive situation
involving quantum agents and pave the way for a range of quantum transaction
applications.Comment: 9 pages, 5 figure
Phage display-derived inhibitor of the essential cell wall biosynthesis enzyme MurF
Background
To develop antibacterial agents having novel modes of action against bacterial cell wall biosynthesis, we targeted the essential MurF enzyme of the antibiotic resistant pathogen Pseudomonas aeruginosa. MurF catalyzes the formation of a peptide bond between D-Alanyl-D-Alanine (D-Ala-D-Ala) and the cell wall precursor uridine 5'-diphosphoryl N-acetylmuramoyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid (UDP-MurNAc-Ala-Glu-meso-A2pm) with the concomitant hydrolysis of ATP to ADP and inorganic phosphate, yielding UDP-N-acetylmuramyl-pentapeptide. As MurF acts on a dipeptide, we exploited a phage display approach to identify peptide ligands having high binding affinities for the enzyme.
Results
Screening of a phage display 12-mer library using purified P. aeruginosa MurF yielded to the identification of the MurFp1 peptide. The MurF substrate UDP-MurNAc-Ala-Glumeso-A2pm was synthesized and used to develop a sensitive spectrophotometric assay to quantify MurF kinetics and inhibition. MurFp1 acted as a weak, time-dependent inhibitor of MurF activity but was a potent inhibitor when MurF was pre-incubated with UDP-MurNAc-Ala-Glu-meso-A2pm or ATP. In contrast, adding the substrate D-Ala-D-Ala during the pre-incubation nullified the inhibition. The IC50 value of MurFp1 was evaluated at 250 μM, and the Ki was established at 420 μM with respect to the mixed type of inhibition against D-Ala-D-Ala.
Conclusion
MurFp1 exerts its inhibitory action by interfering with the utilization of D-Ala-D-Ala by the MurF amide ligase enzyme. We propose that MurFp1 exploits UDP-MurNAc-Ala-Glu-meso-A2pm-induced structural changes for better interaction with the enzyme. We present the first peptide inhibitor of MurF, an enzyme that should be exploited as a target for antimicrobial drug development
Quantum singular-value decomposition of nonsparse low-rank matrices
We present a method to exponentiate nonsparse indefinite low-rank matrices on a quantum computer. Given access to the elements of the matrix, our method allows one to determine the singular values and their associated singular vectors in time exponentially faster in the dimension of the matrix than known classical algorithms. The method extends to non-Hermitian and nonsquare matrices via matrix embedding. Moreover, our method preserves the phase relations between the singular spaces allowing for efficient algorithms that require operating on the entire singular-value decomposition of a matrix. As an example of such an algorithm, we discuss the Procrustes problem of finding a closest isometry to a given matrix
Citric acid cycle enzymes of Methylophilus methylotrophus
SIGLEAvailable from British Library Document Supply Centre- DSC:DX79219 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Relationships Among Measures of Strength and Power and Health Outcomes in Youth
The interest in musculoskeletal fitness and its overall impact on health has been increasing in the last decade. The Institute of Medicine (2012) report called for the addition of several muscular fitness tests to national surveys of youth health-related physical fitness and to fitness test batteries in schools and other educational settings. Purpose: The purpose of this study was to examine the relationships among various muscular fitness tests and health outcomes in youth. Methods: Participants included 49 boys and girls aged 9 to 14 years. A series of muscular fitness tests and tests of health outcomes were completed in two test sessions. Muscular fitness tests included the standing long jump, vertical jump, upper body power throw, total body power throw, and handgrip strength. Handgrip strength was expressed in absolute terms and allometrically scaled to a power of 0.67. The health outcomes examined were aerobic capacity, body composition, systolic blood pressure (SBP), diastolic blood pressure (DBP), and physical activity. Aerobic capacity (VO₂[subscript]max) was directly measured during a maximal treadmill test. Body composition (percent fat) was assessed with the BODPOD. Blood pressure was measured via auscultation after 5 minutes of seated rest. Physical activity was quantified as minutes of moderate-to-vigorous physical activity (MVPA) from 7-day accelerometer measurement. Bivariate correlations were calculated to examine the relationships among fitness tests of strength and power and health outcomes. To control for the impact of body mass index (BMI) and age, partial correlations were calculated among fitness tests and health outcomes controlling for BMI z-score and age. To examine relationships among fitness tests and health outcomes from a criterion-referenced perspective, participants were categorized into both the aerobic capacity and body composition Healthy Fitness Zone (HFZ) and Needs Improvement Zone (NIZ) as defined by FitnessGram®. Effect size (ES) estimates were calculated with Cohen's delta to examine the size of the difference between the HFZ and NIZ groups on the fitness test variables. Results: SBP and VO₂[subscript]max were moderately correlated with several fitness tests, including total body power throw (r = .37, -.28), upper body power throw (r = .33, -.31), and dominant (r = .44, -.33) and nondominant handgrip strength (r = .37, -.34). Percent fat was moderately correlated with the standing long jump (r = -.45) and vertical jump (r = -.50). The correlation between percent fat and handgrip strength was close to zero when handgrip strength was expressed in absolute terms. Moderate correlations were found between percent fat and handgrip strength when handgrip strength was allometrically scaled for body mass (r = -.50 and -.48). When partial correlations controlling for BMI z-score and age were calculated, generally a similar pattern of correlations was found, except that the partial correlations among SBP and the throwing tests and absolute handgrip strength were lower than the bivariate correlations. When the HFZ was defined with aerobic capacity standards, the HFZ group did better on the standing long jump than the NIZ group (ES = 0.45). However, medium effect sizes demonstrated that the NIZ group did better than the HFZ group on total body power throw (ES = -0.42), upper body power throw (ES = -0.59), and absolute handgrip strength (ES = -0.48, -0.39). Differences in the vertical jump and allometrically scaled handgrip strength favored the HFZ group over the NIZ group, but these differences were generally small (range of ES = 0.16 to .32). When the HFZ was defined with body composition standards, effect size estimates revealed large differences between the HFZ and NIZ groups favoring the HFZ group for standing long jump (ES = 0.84), vertical jump (ES = 1.06), and allometrically scaled handgrip strength (ES = 1.30, 1.42). Small to medium effect sizes were found for total body power throw (ES = 0.26), upper body power throw (ES = 0.19), and absolute handgrip strength (ES = 0.36, 0.43) favoring the HFZ group over the NIZ group. Conclusion: Results demonstrated moderate levels of norm-referenced and criterion-referenced evidence that the tests of musculoskeletal fitness used in the current study are health-related. However, findings also indicated that the significant relationships between these musculoskeletal fitness tests and health outcomes are highly influenced by body composition.M.S
Contrasting Multicast Algorithms and XML with Afer
In recent years, much research has been devoted to the simulation of compilers; nevertheless, few have investigated the exploration of web browsers. Given the trends in distributed theory, futurists dubiously note the key unification of RPCs and spreadsheets, which embodies the technical principles of steganography. We confirm that although Web services and semaphores can collaborate to realize this ambition, suffix trees can be made distributed, wireless, and mobile
An efficient quantum algorithm for spectral estimation
We develop an efficient quantum implementation of an important signal
processing algorithm for line spectral estimation: the matrix pencil method,
which determines the frequencies and damping factors of signals consisting of
finite sums of exponentially damped sinusoids. Our algorithm provides a
quantum speedup in a natural regime where the sampling rate is much higher
than the number of sinusoid components. Along the way, we develop techniques
that are expected to be useful for other quantum algorithms as
well—consecutive phase estimations to efficiently make products of asymmetric
low rank matrices classically accessible and an alternative method to
efficiently exponentiate non-Hermitian matrices. Our algorithm features an
efficient quantum–classical division of labor: the time-critical steps are
implemented in quantum superposition, while an interjacent step, requiring
much fewer parameters, can operate classically. We show that frequencies and
damping factors can be obtained in time logarithmic in the number of sampling
points, exponentially faster than known classical algorithms
An analog quantum variational embedding classifier
Quantum machine learning has the potential to provide powerful algorithms for
artificial intelligence. The pursuit of quantum advantage in quantum machine
learning is an active area of research. For current noisy, intermediate-scale
quantum (NISQ) computers, various quantum-classical hybrid algorithms have been
proposed. One such previously proposed hybrid algorithm is a gate-based
variational embedding classifier, which is composed of a classical neural
network and a parameterized gate-based quantum circuit. We propose a quantum
variational embedding classifier based on an analog quantum computer, where
control signals vary continuously in time: our particular focus is
implementation using quantum annealers. In our algorithm, the classical data is
transformed into the parameters of the time-varying Hamiltonian of the analog
quantum computer by a linear transformation. The nonlinearity needed for a
nonlinear classification problem is purely provided by the analog quantum
computer, through the nonlinear dependence of the final quantum state on the
control parameters of the Hamiltonian. We performed numerical simulations that
demonstrate the effectiveness of our algorithm for performing binary and
multi-class classification on linearly inseparable datasets such as concentric
circles and MNIST digits. Our algorithm performs much better than classical
linear classifiers. We find that the performance of our classifier can be
increased by increasing the number of qubits. Our algorithm presents the
possibility to use current quantum annealers for solving practical
machine-learning problems and it could also be useful to explore quantum
advantage in quantum machine learning
- …