246 research outputs found
Assimilating GCOM-W1 AMSR2 and TRMM TMI Radiance Data in GEOS Analysis and Reanalysis
The Tropical Rainfall Measurement Mission (TRMM) Microwave Imager (TMI) observed the Earth in lower latitudes between 1997 - 2015. Its conical-scan radiometer has nine channels and measured microwave radiances between 10 and 89 GHz. These data provide information on atmospheric temperature, humidity, clouds, precipitation, as well as sea surface temperature. Radiance data from other microwave radiometers such as Special Sensor Microwave Imager (SSM/I) and Special Sensor Microwave Imager Sounder (SSMIS) onboard various Defense Meteorological Satellite Program (DMSP) satellites are assimilated in clear-sky conditions in the Modern-Era Retrospective analysis for Research and Applications (MERRA) and its version 2 (MERRA-2) data sets at the Global Modeling and Assimilation Office (GMAO) at NASA Goddard Space Flight Center. The GMAO's Hybrid 4D-EnVar-based Atmospheric Data Assimilation System (ADAS) is enhanced with an all-sky microwave radiance data assimilation capability in the real-time GEOS-Forward Processing (FP) system. Currently, the FP system assimilates Global Precipitation Measurement (GPM) microwave imager (GMI) radiance data utilizing this all-sky capability, and is being extended to use more all-sky data from other microwave radiometers. In this presentation, we will focus on impacts of all-sky TMI radiance data on GEOS analyses of atmospheric moisture, precipitation and other fields, and discuss their applications for future GEOS reanalyses
Single-qubit unitary gates by graph scattering
We consider the effects of plane-wave states scattering off finite graphs, as
an approach to implementing single-qubit unitary operations within the
continuous-time quantum walk framework of universal quantum computation. Four
semi-infinite tails are attached at arbitrary points of a given graph,
representing the input and output registers of a single qubit. For a range of
momentum eigenstates, we enumerate all of the graphs with up to vertices
for which the scattering implements a single-qubit gate. As increases, the
number of new unitary operations increases exponentially, and for the
majority correspond to rotations about axes distributed roughly uniformly
across the Bloch sphere. Rotations by both rational and irrational multiples of
are found.Comment: 8 pages, 7 figure
Recurrence of biased quantum walks on a line
The Polya number of a classical random walk on a regular lattice is known to
depend solely on the dimension of the lattice. For one and two dimensions it
equals one, meaning unit probability to return to the origin. This result is
extremely sensitive to the directional symmetry, any deviation from the equal
probability to travel in each direction results in a change of the character of
the walk from recurrent to transient. Applying our definition of the Polya
number to quantum walks on a line we show that the recurrence character of
quantum walks is more stable against bias. We determine the range of parameters
for which biased quantum walks remain recurrent. We find that there exist
genuine biased quantum walks which are recurrent.Comment: Journal reference added, minor corrections in the tex
Course of action taken by smear negative chest symptomatics: A report from a rural area in South India
Objective: To evaluate adherence to diagnostic algorithm of Revised National Tuberculosis Control Programme (RNTCP)
and course of action taken by smear-negative chest symptomatics (CSs).
Method: Interviewing smear-negative chest symptomatics.
Results: Of the 423 smear-negative CSs interviewed, 85 (20%) were not prescribed antibiotics and only 133 (39%)
received it for more than seven days. Of the 148 patients with persistence of symptoms, 83 (56%) returned for further
investigations and only 39% were X-rayed. Main reasons for not returning were: ‘not aware’ or ‘consulted another health
provider.’
Conclusion: Strict adherence to diagnostic algorithm and proper counselling of patients are important for diagnosing
smear-negative pulmonary tuberculosis (PTB) cases
New Developments in Quantum Algorithms
In this survey, we describe two recent developments in quantum algorithms.
The first new development is a quantum algorithm for evaluating a Boolean
formula consisting of AND and OR gates of size N in time O(\sqrt{N}). This
provides quantum speedups for any problem that can be expressed via Boolean
formulas. This result can be also extended to span problems, a generalization
of Boolean formulas. This provides an optimal quantum algorithm for any Boolean
function in the black-box query model.
The second new development is a quantum algorithm for solving systems of
linear equations. In contrast with traditional algorithms that run in time
O(N^{2.37...}) where N is the size of the system, the quantum algorithm runs in
time O(\log^c N). It outputs a quantum state describing the solution of the
system.Comment: 11 pages, 1 figure, to appear as an invited survey talk at MFCS'201
Coined quantum walks on percolation graphs
Quantum walks, both discrete (coined) and continuous time, form the basis of
several quantum algorithms and have been used to model processes such as
transport in spin chains and quantum chemistry. The enhanced spreading and
mixing properties of quantum walks compared with their classical counterparts
have been well-studied on regular structures and also shown to be sensitive to
defects and imperfections in the lattice. As a simple example of a disordered
system, we consider percolation lattices, in which edges or sites are randomly
missing, interrupting the progress of the quantum walk. We use numerical
simulation to study the properties of coined quantum walks on these percolation
lattices in one and two dimensions. In one dimension (the line) we introduce a
simple notion of quantum tunneling and determine how this affects the
properties of the quantum walk as it spreads. On two-dimensional percolation
lattices, we show how the spreading rate varies from linear in the number of
steps down to zero, as the percolation probability decreases to the critical
point. This provides an example of fractional scaling in quantum walk dynamics.Comment: 25 pages, 14 figures; v2 expanded and improved presentation after
referee comments, added extra figur
Correlated Markov Quantum Walks
We consider the discrete time unitary dynamics given by a quantum walk on
performed by a particle with internal degree of freedom, called coin
state, according to the following iterated rule: a unitary update of the coin
state takes place, followed by a shift on the lattice, conditioned on the coin
state of the particle. We study the large time behavior of the quantum
mechanical probability distribution of the position observable in for
random updates of the coin states of the following form. The random sequences
of unitary updates are given by a site dependent function of a Markov chain in
time, with the following properties: on each site, they share the same
stationnary Markovian distribution and, for each fixed time, they form a
deterministic periodic pattern on the lattice.
We prove a Feynman-Kac formula to express the characteristic function of the
averaged distribution over the randomness at time in terms of the nth power
of an operator . By analyzing the spectrum of , we show that this
distribution posesses a drift proportional to the time and its centered
counterpart displays a diffusive behavior with a diffusion matrix we compute.
Moderate and large deviations principles are also proven to hold for the
averaged distribution and the limit of the suitably rescaled corresponding
characteristic function is shown to satisfy a diffusion equation.
An example of random updates for which the analysis of the distribution can
be performed without averaging is worked out. The random distribution displays
a deterministic drift proportional to time and its centered counterpart gives
rise to a random diffusion matrix whose law we compute. We complete the picture
by presenting an uncorrelated example.Comment: 37 pages. arXiv admin note: substantial text overlap with
arXiv:1010.400
Practical implementation of a quantum backtracking algorithm
In previous work, Montanaro presented a method to obtain quantum speedups for
backtracking algorithms, a general meta-algorithm to solve constraint
satisfaction problems (CSPs). In this work, we derive a space efficient
implementation of this method. Assume that we want to solve a CSP with
constraints on variables and that the union of the domains in which these
variables take their value is of cardinality . Then, we show that the
implementation of Montanaro's backtracking algorithm can be done by using data qubits. We detail an implementation of the predicate associated
to the CSP with an additional register of qubits. We explicit our
implementation for graph coloring and SAT problems, and present simulation
results. Finally, we discuss the impact of the usage of static and dynamic
variable ordering heuristics in the quantum setting.Comment: 18 pages, 10 figure
The timing of death in patients with tuberculosis who die during anti-tuberculosis treatment in Andhra Pradesh, South India
Background: India has 2.0 million estimated tuberculosis (TB) cases per annum with an estimated 280,000 TBrelated
deaths per year. Understanding when in the course of TB treatment patients die is important for
determining the type of intervention to be offered and crucially when this intervention should be given. The
objectives of the current study were to determine in a large cohort of TB patients in India:- i) treatment outcomes
including the number who died while on treatment, ii) the month of death and iii) characteristics associated with
“early” death, occurring in the initial 8 weeks of treatment.
Methods: This was a retrospective study in 16 selected Designated Microscopy Centres (DMCs) in Hyderabad,
Krishna and Adilabad districts of Andhra Pradesh, South India. A review was performed of treatment cards and
medical records of all TB patients (adults and children) registered and placed on standardized anti-tuberculosis
treatment from January 2005 to September 2009.
Results: There were 8,240 TB patients (5183 males) of whom 492 (6%) were known to have died during treatment.
Case-fatality was higher in those previously treated (12%) and lower in those with extra-pulmonary TB (2%). There
was an even distribution of deaths during anti-tuberculosis treatment, with 28% of all patients dying in the first 8
weeks of treatment. Increasing age and new as compared to recurrent TB disease were significantly associated
with “early death”.
Conclusion: In this large cohort of TB patients, deaths occurred with an even frequency throughout anti-TB
treatment. Reasons may relate to i) the treatment of the disease itself, raising concerns about drug adherence,
quality of anti-tuberculosis drugs or the presence of undetected drug resistance and ii) co-morbidities, such as HIV/
AIDS and diabetes mellitus, which are known to influence mortality. More research in this area from prospective
and retrospective studies is needed
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