1,315 research outputs found
Macrofossils and pollen representing forests of the pre-Taupo volcanic eruption (c. 1850 yr BP) era at Pureora and Benneydale, central North Island, New Zealand.
Micro- and macrofossil data from the remains of forests overwhelmed and buried at Pureora and Benneydale during the Taupo eruption (c. 1850 conventional radiocarbon yr BP) were compared. Classification of relative abundance data separated the techniques, rather than the locations, because the two primary clusters comprised pollen and litter/wood. This indicates that the pollen:litter/wood within-site comparisons (Pureora and Benneydale are 20 km apart) are not reliable. Plant macrofossils represented mainly local vegetation, while pollen assemblages represented a combination of local and regional vegetation. However, using ranked abundance and presence/absence data, both macrofossils and pollen at Pureora and Benneydale indicated conifer/broadleaved forest, of similar forest type and species composition at each site. This suggests that the forests destroyed by the eruption were typical of mid-altitude west Taupo forests, and that either data set (pollen or macrofossils) would have been adequate for regional forest interpretation.
The representation of c. 1850 yr BP pollen from the known buried forest taxa was generally consistent with trends determined by modern comparisons between pollen and their source vegetation, but with a few exceptions.
A pollen profile from between the Mamaku Tephra (c. 7250 yr BP) and the Taupo Ignimbrite indicated that the Benneydale forest had been markedly different in species dominance compared with the forest that was destroyed during the Taupo eruption. These differences probably reflect changes in drainage, and improvements in climate and/or soil fertility over the middle Holocene
Input Sparsity and Hardness for Robust Subspace Approximation
In the subspace approximation problem, we seek a k-dimensional subspace F of
R^d that minimizes the sum of p-th powers of Euclidean distances to a given set
of n points a_1, ..., a_n in R^d, for p >= 1. More generally than minimizing
sum_i dist(a_i,F)^p,we may wish to minimize sum_i M(dist(a_i,F)) for some loss
function M(), for example, M-Estimators, which include the Huber and Tukey loss
functions. Such subspaces provide alternatives to the singular value
decomposition (SVD), which is the p=2 case, finding such an F that minimizes
the sum of squares of distances. For p in [1,2), and for typical M-Estimators,
the minimizing gives a solution that is more robust to outliers than that
provided by the SVD. We give several algorithmic and hardness results for these
robust subspace approximation problems.
We think of the n points as forming an n x d matrix A, and letting nnz(A)
denote the number of non-zero entries of A. Our results hold for p in [1,2). We
use poly(n) to denote n^{O(1)} as n -> infty. We obtain: (1) For minimizing
sum_i dist(a_i,F)^p, we give an algorithm running in O(nnz(A) +
(n+d)poly(k/eps) + exp(poly(k/eps))), (2) we show that the problem of
minimizing sum_i dist(a_i, F)^p is NP-hard, even to output a
(1+1/poly(d))-approximation, answering a question of Kannan and Vempala, and
complementing prior results which held for p >2, (3) For loss functions for a
wide class of M-Estimators, we give a problem-size reduction: for a parameter
K=(log n)^{O(log k)}, our reduction takes O(nnz(A) log n + (n+d) poly(K/eps))
time to reduce the problem to a constrained version involving matrices whose
dimensions are poly(K eps^{-1} log n). We also give bicriteria solutions, (4)
Our techniques lead to the first O(nnz(A) + poly(d/eps)) time algorithms for
(1+eps)-approximate regression for a wide class of convex M-Estimators.Comment: paper appeared in FOCS, 201
The Alaska Marriage Amendment: The Peopleās Choice on the Last Frontier
I Sverige beraĢknas 17 % av befolkningen ha en hoĢrselnedsaĢttning, vilket innebaĢr att det aĢr den vanligaste sensoriska funktionsnedsaĢttningen. Idag finns det en maĢngd studier som visar att hoĢrselnedsaĢttning aĢr relaterat till saĢmre psykisk haĢlsa. Acceptans av sin hoĢrselnedsaĢttning har visat sig vara positivt foĢr hoĢrselnedsatta och samvarierar med hjaĢlpsoĢkande. Acceptance and commitment therapy (ACT) aĢr en transdiagnostisk behandling daĢr psykopatologi antas bero paĢ en hoĢg grad av upplevelsemaĢssigt undvikande och fusion med tankar. MaĢlet i ACT aĢr att oĢka psykologisk flexibilitet daĢr acceptans aĢr en betydande komponent. Denna explorativa studie undersoĢkte foĢraĢndringsprocesser i ACT foĢr personer med hoĢrselnedsaĢttning daĢr utfallet var kaĢnslomaĢssig och social anpassning foĢr hoĢrselnedsaĢttningen (HHIE-S). De foĢraĢndringsprocesser som proĢvades var acceptans (HAQ), som tidigare visat paĢ medierande effekt foĢr ACT, samt tvaĢ alternativa foĢraĢndringsprocesser; self-efficacy (HSE-4) och upplevd stress (PSS-4). Behandlingen bestod av aĢtta internetadministrerade moduler givna med behandlarstoĢd daĢr veckovisa maĢtningar av foĢraĢndringsprocesser och utfall anvaĢndes. Studiens resultat visar att behandlingsgruppen upplevde marginellt signifikant mindre problem med kaĢnslomaĢssig och social anpassning foĢr hoĢrselnedsaĢttningen (HHIE-S). Studiens resultat pekar paĢ att hoĢrselrelaterad acceptans (HAQ) och self- efficacy (HSE-4) medierar behandlingens effekt paĢ deltagarnas kaĢnslomaĢssiga och sociala anpassning foĢr hoĢrselnedsaĢttning (HHIE-S). SaĢledes tillfoĢr denna studie ytterligare belaĢgg foĢr acceptans som foĢraĢndringsprocess i ACT. AĢven self-efficacy kan vara en intressant mediator att beakta i fortsatt forskning.
Study of pion-proton backward elastic scattering in the centre of mass energy range 2.1 to 2.4 GeV
SIGLELD:D45266/83 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
The Problem of Patent Thickets in Convergent Technologies
Patent thickets are unintentionally dense webs of overlapping intellectual property rights owned by different companies that can retard progress. This article begins with a review of existing research on patent thickets, focusing in particular on the problem of patent thickets in nanotechnology, or nanothickets. After presenting visual evidence of the presence of nanothickets using a network analytic technique, it discusses potential organizational responses to patent thickets. It then reviews the existing research on patent pools and discusses pool formation in the shadow of antitrust enforcement. Based on recent research on patent pool formation, it examines the divergent fate of two recent pools and discusses the prospects for the future formation of nanotechnology patent pools, or nanopools.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72678/1/annals.1382.014.pd
Issues facing Southlandās wetlandsā recommendations for future management
This report summarises our experiences and recommendations from a weeklong series of fieldtrips and workshops focused on Southlandās wetlands.
Our major recommendations are:
ā¢ Priorities must be developed for wetland protection and restoration, according to which wetland systems have suffered the greatest losses and which are least represented in the reserves network.
ā¢ The development of educational and interpretive resources and programmes will help to raise the level of awareness of the unique values of Southlandās wetlands amongst landowners, local authorities and the public, and will provide opportunities for regional promotion and ecotourism.
ā¢ There is a need for more research to: increase levels of understanding of wetland development and function; threats from weed invasion and effective control methods; and to design and monitor effective restoration efforts. Some of this research could be achieved thorough ongoing communication with PGSF-funded research organisations and universities, eg. BSc (Hons) and MSc thesis topics.
ā¢ Protect the hydrological functioning of wetlands, by developing guidelines for drainage practices in land adjacent to wetlands, and reducing nutrient loading of surface and groundwaters flowing into wetlands.
ā¢ Incorporate principles of wetland protection into regional and district plans
The use of chronosequences in studies of ecological succession and soil development
1. Chronosequences and associated space-for-time substitutions are an important and often necessary tool for studying temporal dynamics of plant communities and soil development across multiple time-scales. However, they are often used inappropriately, leading to false conclusions about ecological patterns and processes, which has prompted recent strong criticism of the approach. Here, we evaluate when chronosequences may or may not be appropriate for studying community and ecosystem development.
2. Chronosequences are appropriate to study plant succession at decadal to millennial time-scales when there is evidence that sites of different ages are following the same trajectory. They can also be reliably used to study aspects of soil development that occur between temporally linked sites over time-scales of centuries to millennia, sometimes independently of their application to shorter-term plant and soil biological communities.
3. Some characteristics of changing plant and soil biological communities (e.g. species richness, plant cover, vegetation structure, soil organic matter accumulation) are more likely to be related in a predictable and temporally linear manner than are other characteristics (e.g. species composition and abundance) and are therefore more reliably studied using a chronosequence approach.
4. Chronosequences are most appropriate for studying communities that are following convergent successional trajectories and have low biodiversity, rapid species turnover and low frequency and severity of disturbance. Chronosequences are least suitable for studying successional trajectories that are divergent, species-rich, highly disturbed or arrested in time because then there are often major difficulties in determining temporal linkages between stages.
5. Synthesis. We conclude that, when successional trajectories exceed the life span of investigators and the experimental and observational studies that they perform, temporal change can be successfully explored through the judicious use of chronosequences
- ā¦