16,765 research outputs found
Semantic categories underlying the meaning of ‘place’
This paper analyses the semantics of natural language expressions that are associated with the intuitive notion of ‘place’. We note that the nature of such terms is highly contested, and suggest that this arises from two main considerations: 1) there are a number of logically
distinct categories of place expression, which are not always clearly distinguished in discourse about ‘place’; 2) the many non-substantive place count nouns (such as ‘place’, ‘region’, ‘area’, etc.) employed in natural
language are highly ambiguous. With respect to consideration 1), we propose that place-related expressions
should be classified into the following distinct logical types: a) ‘place-like’ count nouns (further subdivided into abstract, spatial and substantive varieties), b) proper names of ‘place-like’ objects, c) locative property phrases, and d) definite descriptions of ‘place-like’ objects. We outline possible formal representations for each of these. To address consideration 2), we examine meanings, connotations and ambiguities of the English vocabulary of abstract and generic place count nouns, and identify underlying elements of meaning, which explain both
similarities and differences in the sense and usage of the various terms
Range Queries on Uncertain Data
Given a set of uncertain points on the real line, each represented by
its one-dimensional probability density function, we consider the problem of
building data structures on to answer range queries of the following three
types for any query interval : (1) top- query: find the point in that
lies in with the highest probability, (2) top- query: given any integer
as part of the query, return the points in that lie in
with the highest probabilities, and (3) threshold query: given any threshold
as part of the query, return all points of that lie in with
probabilities at least . We present data structures for these range
queries with linear or nearly linear space and efficient query time.Comment: 26 pages. A preliminary version of this paper appeared in ISAAC 2014.
In this full version, we also present solutions to the most general case of
the problem (i.e., the histogram bounded case), which were left as open
problems in the preliminary versio
Integration of gender considerations in climate-smart agriculture R4D in South Asia: Useful research questions
Aimed at researchers working with climate-smart agriculture in South Asia, this resource suggests a set of issues to consider in relation to the integration of gender in climate-smart agricultural research for development. Climate change often exacerbates the problems and inequities that poor rural women face. The feminization of agriculture underscores the need to ensure that both men and women are able to learn about, try out, take up, and benefit from improved agricultural technologies, including climate-smart practices
The Computational Power of Optimization in Online Learning
We consider the fundamental problem of prediction with expert advice where
the experts are "optimizable": there is a black-box optimization oracle that
can be used to compute, in constant time, the leading expert in retrospect at
any point in time. In this setting, we give a novel online algorithm that
attains vanishing regret with respect to experts in total
computation time. We also give a lower bound showing
that this running time cannot be improved (up to log factors) in the oracle
model, thereby exhibiting a quadratic speedup as compared to the standard,
oracle-free setting where the required time for vanishing regret is
. These results demonstrate an exponential gap between
the power of optimization in online learning and its power in statistical
learning: in the latter, an optimization oracle---i.e., an efficient empirical
risk minimizer---allows to learn a finite hypothesis class of size in time
. We also study the implications of our results to learning in
repeated zero-sum games, in a setting where the players have access to oracles
that compute, in constant time, their best-response to any mixed strategy of
their opponent. We show that the runtime required for approximating the minimax
value of the game in this setting is , yielding
again a quadratic improvement upon the oracle-free setting, where
is known to be tight
The Royal Free Hospital score: a calibrated prognostic model for patients with cirrhosis admitted to intensive care unit. Comparison with current models and CLIF-SOFA score
Prognosis for patients with cirrhosis admitted to intensive care unit (ICU) is poor. ICU prognostic models are more accurate than liver-specific models. We identified predictors of mortality, developed a novel prognostic score (Royal Free Hospital (RFH) score), and tested it against established prognostic models and the yet unvalidated Chronic Liver Failure-Sequential Organ Failure Assessment (CLIF-SOFA) model
A tight lower bound instance for k-means++ in constant dimension
The k-means++ seeding algorithm is one of the most popular algorithms that is
used for finding the initial centers when using the k-means heuristic. The
algorithm is a simple sampling procedure and can be described as follows: Pick
the first center randomly from the given points. For , pick a point to
be the center with probability proportional to the square of the
Euclidean distance of this point to the closest previously chosen
centers.
The k-means++ seeding algorithm is not only simple and fast but also gives an
approximation in expectation as shown by Arthur and Vassilvitskii.
There are datasets on which this seeding algorithm gives an approximation
factor of in expectation. However, it is not clear from these
results if the algorithm achieves good approximation factor with reasonably
high probability (say ). Brunsch and R\"{o}glin gave a dataset where
the k-means++ seeding algorithm achieves an approximation ratio
with probability that is exponentially small in . However, this and all
other known lower-bound examples are high dimensional. So, an open problem was
to understand the behavior of the algorithm on low dimensional datasets. In
this work, we give a simple two dimensional dataset on which the seeding
algorithm achieves an approximation ratio with probability
exponentially small in . This solves open problems posed by Mahajan et al.
and by Brunsch and R\"{o}glin.Comment: To appear in TAMC 2014. arXiv admin note: text overlap with
arXiv:1306.420
Analysis of MAGSAT data of the Indian region
Progress in the development of software for reading MAGSAT data tapes and for the reduction of anomaly data, and in the preparation of data for magnetic anomaly maps is reported
Control of atomic decay rates via manipulation of reservoir mode frequencies
We analyse the problem of a two-level atom interacting with a time-dependent
dissipative environment modelled by a bath of reservoir modes. In the model of
this paper the principal features of the reservoir structure remain constant in
time, but the microscopic structure does not. In the context of an atom in a
leaky cavity this corresponds to a fixed cavity and a time-dependent external
bath. In this situation we show that by chirping the reservoir modes
sufficiently fast it is possible to inhibit, or dramatically enhance the decay
of the atomic system, even though the gross reservoir structure is fixed. Thus
it is possible to extract energy from a cavity-atom system faster than the
empty cavity rate. Similar, but less dramatic effects are possible for moderate
chirps where partial trapping of atomic population is also possible.Comment: 12 pages, 9 figure
Effect of 5-hydroxytryptamine and related compounds on the isolated heart of Pila globosa (Gastropoda:Mollusca)
5-Hydroxytryptamine produces an increase in the amplitude and frequency of the heart-beat of Pila. The threshold for the activity of 5-hydroxytryptamine is 10−8 gm./ml. However, this dose is not constant. In some cases it is 10−6 gm./ml. and in still other cases doses even upto 10−4 gm./ml. are ineffective. The action of 5-HT is not blocked by LSD. However, LSD 10−5 gm./ml. produces a positive inotropic and a very slight positive chronotropic response. The bromine derivative of LSD sometimes causes a rise in the threshold of 5-HT. Reserpine produces a positive inotropic and a negative chronotropic effect. The threshold dose for Reserpine is 10−5 gm./ml. The action of Reserpine is of long duration and both increase in amplitude and decrease in frequency go on for a long time in a progressive manner. The action of 5-HT and related compounds on the heart of Pila has been discussed in relation to that in other molluscs
A saline medium for maintaining isolated heart of Pila globosa, Swainson
Some known standard salines for molluscs were found unsuitable for maintaining the heart of Pila in vitro. A new saline for Pila has been devised keeping in view the ionic composition, pH and osmotic pressure of blood of Pila. A saline having the composition of blood was not found suitable for maintaining isolated heart of Pila but reduction of percentage of potassium made it so. The osmotic pressure was adjusted with addition of glucose which also provides energy. Changes of pH between 5 and 8·5 did not have an effect on the heart-beat of Pila. It was suggested that a saline containing only the principal ions of blood was not suitable because other trace and organic substances present in the blood were perhaps playing an important role in the regular beating of the heart. Adjustment in the proportion of different ions and addition of glucose did partly compensate for the absence of these substances
- …