555 research outputs found
The Relationship between Photosynthesis and Irradiance for Gulf of California Phytoplankton
During June 17-28, 1982, we carried on experiments to generate
photosynthesis-irradiance curves for phytoplankton from five locations of the
central and northern Gulf of California. Using natural sunlight, on board 14C
incubations were done with samples collected from five different depths within
the euphotic zone. In general there were great vertical changes of variables
controlling primary productivity, even in cases where weak vertical TOC gradients
indicated high instability and mixing of the euphotic zone. The assimilation
number (PBm) had a two fold variation within the mixed layer. In general PBm
decreased monotonically with depth due to phytoplankton conditioning to lower
irradiances. Surface PBm values had a range of 8 to 15mg C. mg Chl a- 1. h-1.
When a thermocline was present, PBm for the bottom of the euphotic zone was
about 4 to 10% of that for surface waters. But, without a thermocline, P~ for
the bottom of the euphotic zone was ~ 60% of that for surface waters, due to
turbulence moving phytoplankton up and down the water column. Diatoms
were abundant in three stations near Angel de la Guarda and Tiburon islands.
For the station at the central gulf and the one at the very northern gulf, very few
nano and microplankton were found with the inverted scope technique, but high
chlorophyll concentrations and primary productivity indicated a high abundance
of picoplankton. This difference in plankton size composition was not
reflected in PBm values. Nutrient concentrations were high and did not limit PBm
values. Our PBm values are higher than those reported for the gulf's winter
phytoplankton; and they are about two times higher than those for winter
phytoplankton of the oceanic region between San Diego and Acapulco. Our
Gulf of California integrated primary productivity values had a range of 1.3 to
4.4gC. m-2. d-1
High frequency longitudinal and transverse dynamics in water
High-resolution, inelastic x-ray scattering measurements of the dynamic
structure factor S(Q,\omega) of liquid water have been performed for wave
vectors Q between 4 and 30 nm^-1 in distinctly different thermodynamic
conditions (T= 263 - 420 K ; at, or close to, ambient pressure and at P = 2
kbar). In agreement with previous inelastic x-ray and neutron studies, the
presence of two inelastic contributions (one dispersing with Q and the other
almost non-dispersive) is confirmed. The study of their temperature- and
Q-dependence provides strong support for a dynamics of liquid water controlled
by the structural relaxation process. A viscoelastic analysis of the
Q-dispersing mode, associated with the longitudinal dynamics, reveals that the
sound velocity undergoes the complete transition from the adiabatic sound
velocity (c_0) (viscous limit) to the infinite frequency sound velocity
(c_\infinity) (elastic limit). On decreasing Q, as the transition regime is
approached from the elastic side, we observe a decrease of the intensity of the
second, weakly dispersing feature, which completely disappears when the viscous
regime is reached. These findings unambiguously identify the second excitation
to be a signature of the transverse dynamics with a longitudinal symmetry
component, which becomes visible in the S(Q,\omega) as soon as the purely
viscous regime is left.Comment: 28 pages, 12 figure
Lower Critical Dimension of Ising Spin Glasses
Exact ground states of two-dimensional Ising spin glasses with Gaussian and
bimodal (+- J) distributions of the disorder are calculated using a
``matching'' algorithm, which allows large system sizes of up to N=480^2 spins
to be investigated. We study domain walls induced by two rather different types
of boundary-condition changes, and, in each case, analyze the system-size
dependence of an appropriately defined ``defect energy'', which we denote by
DE. For Gaussian disorder, we find a power-law behavior DE ~ L^\theta, with
\theta=-0.266(2) and \theta=-0.282(2) for the two types of boundary condition
changes. These results are in reasonable agreement with each other, allowing
for small systematic effects. They also agree well with earlier work on smaller
sizes. The negative value indicates that two dimensions is below the lower
critical dimension d_c. For the +-J model, we obtain a different result, namely
the domain-wall energy saturates at a nonzero value for L\to \infty, so \theta
= 0, indicating that the lower critical dimension for the +-J model exactly
d_c=2.Comment: 4 pages, 4 figures, 1 table, revte
A Transient New Coherent Condition of Matter: The Signal for New Physics in Hadronic Diffractive Scattering
We demonstrate the existence of an anomalous structure in the data on the
diffractive elastic scattering of hadrons at high energies and small momentum
transfer. We analyze five sets of experimental data on
scattering from five different experiments with colliding beams, ranging from
the first-- and second--generation experiments at GeV to the
most recent experiments at 546 GeV and at 1800 GeV. All of the data sets
exhibit a localized anomalous structure in momentum transfer. We represent the
anomalous behavior by a phenomenological formula. This is based upon the idea
that a transient coherent condition of matter occurs in some of the
intermediate inelastic states which give rise, via unitarity, to diffractive
elastic scattering. The Fourier--Bessel transform into momentum--transfer space
of a spatial oscillatory behavior of matter in the impact--parameter plane
results in a small piece of the diffractive amplitude which exhibits a
localized anomalous behavior near a definite value of . In addition, we
emphasize possible signals coming directly from such a new condition of matter
that may be present in current experiments on inelastic processes.Comment: 25 pages, LaTeX (12 figures, not included). A complete postscript
file (except figures 1 and 11, which are available upon request) is available
via anonymous ftp at ttpux2.physik.uni-karlsruhe.de (129.13.102.139) as
/ttp94-03 /ttp94-03.ps, Local preprint# TTP94-03 (March 1994
Generating droplets in two-dimensional Ising spin glasses by using matching algorithms
We study the behavior of droplets for two dimensional Ising spin glasses with
Gaussian interactions. We use an exact matching algorithm which enables study
of systems with linear dimension L up to 240, which is larger than is possible
with other approaches. But the method only allows certain classes of droplets
to be generated. We study single-bond, cross and a category of fixed volume
droplets as well as first excitations. By comparison with similar or equivalent
droplets generated in previous works, the advantages but also the limitations
of this approach are revealed. In particular we have studied the scaling
behavior of the droplet energies and droplet sizes. In most cases, a crossover
of the data can be observed such that for large sizes the behavior is
compatible with the one-exponent scenario of the droplet theory. Only for the
case of first excitations, no clear conclusion can be reached, probably because
even with the matching approach the accessible system sizes are still too
small.Comment: 11 pages, 16 figures, revte
Study protocol: young carers and young adult carers in Switzerland
Background: In Switzerland, the issue of young carers and young adult carers - young people under the age of 18 and 24 respectively, who take on significant or substantial caring tasks and levels of responsibility that would usually be associated with an adult - has not been researched before. The number of these younger carers is unknown, as is the extent and kind of their caring activities and the outcomes for their health, well-being, psycho-social development, education, transitions to adulthood, future employability and economic participation.
Methods: The project is comprised of three stages:
1. A national Swiss-wide online survey to examine awareness of the issue of younger carers amongst professional populations in the education, health and social services sectors;
2. An online survey of 4800 Swiss pupils in schools using standardised instruments to identify the proportion and characteristics of pupils who are carers; and
3. Semi-structured interviews with 20 families comprising family members with care needs and younger carers, to consolidate and validate the other stages of the study; and to hear directly from care-dependent family members and younger carers about their experiences of the issues identified in the surveys and in previous published research.
Discussion: The needs of younger carers and their ill and disabled family members in Switzerland have not been systematically investigated. This will be the first study in the country to investigate these issues and to develop evidence-based recommendations for policy and practice, drawing also on international research. The present study therefore fills an important national and international research gap. It will collect important data on the awareness, extent, kind and impact of caring amongst children and young people in Switzerland, and cross-link these findings with robust evidence from other countries. The study will reveal (a) the extent of awareness of the issue of young carers amongst medical, social, health, educational, and other groups in Switzerland; (b) the proportion and number of young carers amongst a normative child population, and what these young carers ‘do’ in terms of their caring roles; and (c) direct accounts by families of their care-giving and receiving experiences
Ecology: a prerequisite for malaria elimination and eradication
* Existing front-line vector control measures, such as insecticide-treated nets and residual sprays, cannot break the transmission cycle of Plasmodium falciparum in the most intensely endemic parts of Africa and the Pacific
* The goal of malaria eradication will require urgent strategic investment into understanding the ecology and evolution of the mosquito vectors that transmit malaria
* Priority areas will include understanding aspects of the mosquito life cycle beyond the blood feeding processes which directly mediate malaria transmission
* Global commitment to malaria eradication necessitates a corresponding long-term commitment to vector ecolog
Analysis of cardiac signals using spatial filling index and time-frequency domain
BACKGROUND: Analysis of heart rate variation (HRV) has become a popular noninvasive tool for assessing the activities of the autonomic nervous system (ANS). HRV analysis is based on the concept that fast fluctuations may specifically reflect changes of sympathetic and vagal activity. It shows that the structure generating the signal is not simply linear, but also involves nonlinear contributions. These signals are essentially non-stationary; may contain indicators of current disease, or even warnings about impending diseases. The indicators may be present at all times or may occur at random in the time scale. However, to study and pinpoint abnormalities in voluminous data collected over several hours is strenuous and time consuming. METHODS: This paper presents the spatial filling index and time-frequency analysis of heart rate variability signal for disease identification. Renyi's entropy is evaluated for the signal in the Wigner-Ville and Continuous Wavelet Transformation (CWT) domain. RESULTS: This Renyi's entropy gives lower 'p' value for scalogram than Wigner-Ville distribution and also, the contours of scalogram visually show the features of the diseases. And in the time-frequency analysis, the Renyi's entropy gives better result for scalogram than the Wigner-Ville distribution. CONCLUSION: Spatial filling index and Renyi's entropy has distinct regions for various diseases with an accuracy of more than 95%
Assessing the effects of global warming and local social and economic conditions on the malaria transmission
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