858 research outputs found
Geophysical studies with laser-beam detectors of gravitational waves
The existing high technology laser-beam detectors of gravitational waves may
find very useful applications in an unexpected area - geophysics. To make
possible the detection of weak gravitational waves in the region of high
frequencies of astrophysical interest, ~ 30 - 10^3 Hz, control systems of laser
interferometers must permanently monitor, record and compensate much larger
external interventions that take place in the region of low frequencies of
geophysical interest, ~ 10^{-5} - 3 X 10^{-3} Hz. Such phenomena as tidal
perturbations of land and gravity, normal mode oscillations of Earth,
oscillations of the inner core of Earth, etc. will inevitably affect the
performance of the interferometers and, therefore, the information about them
will be stored in the data of control systems. We specifically identify the
low-frequency information contained in distances between the interferometer
mirrors (deformation of Earth) and angles between the mirrors' suspensions
(deviations of local gravity vectors and plumb lines). We show that the access
to the angular information may require some modest amendments to the optical
scheme of the interferometers, and we suggest the ways of doing that. The
detailed evaluation of environmental and instrumental noises indicates that
they will not prevent, even if only marginally, the detection of interesting
geophysical phenomena. Gravitational-wave instruments seem to be capable of
reaching, as a by-product of their continuous operation, very ambitious
geophysical goals, such as observation of the Earth's inner core oscillations.Comment: 29 pages including 8 figures, modifications and clarifications in
response to referees' comments, to be published in Class. Quant. Gra
A randomised phase II multicentre trial of irinotecan (CPT-11) using four different schedules in patients with metastatic colorectal cancer
The purpose of this phase II trial was to compare the efficacy, safety and pharmacokinetics of four irinotecan schedules for the treatment of metastatic colorectal cancer. In total, 174 5-fluorouracil pretreated patients were randomised to: arm A (n=41), 350 mg m(-2) irinotecan as a 90-min i.v. infusion q3 weeks; arm B (n=38), 125 mg m(-2) irinotecan as a 90-min i.v. infusion weekly x 4 weeks q6 weeks; arm C (n=46), 250 mg m(-2) irinotecan as a 90-min i.v. infusion q2 weeks; or arm D (n=49), 10 mg m(-2) day(-1) irinotecan as a 14-day continuous infusion q3 weeks. No significant differences in efficacy across the four arms were observed, although a shorter time to treatment failure was noted for arm D (1.7 months; P=0.02). Overall response rates were in the range 5-11%. Secondary end points included median survival (6.4-9.4 months), and time to progression (2.7-3.8 months) and treatment failure (1.7-3.2 months). Similarly, there were no significant differences in the incidence of grade 3-4 toxicities, although the toxicity profile between arms A, B, and C and D did differ. Generally, significantly less haematologic toxicity, alopecia and cholinergic syndrome were observed in arm D; however, there was a trend for increased gastrointestinal toxicity. Irinotecan is an effective and safe second-line treatment for colorectal cancer. The schedules examined yielded equivalent results, indicating that there is no advantage of the prolonged vs short infusion schedule
Modelling charge self-trapping in wide-gap dielectrics: Localization problem in local density functionals
We discuss the adiabatic self-trapping of small polarons within the density
functional theory (DFT). In particular, we carried out plane-wave
pseudo-potential calculations of the triplet exciton in NaCl and found no
energy minimum corresponding to the self-trapped exciton (STE) contrary to the
experimental evidence and previous calculations. To explore the origin of this
problem we modelled the self-trapped hole in NaCl using hybrid density
functionals and an embedded cluster method. Calculations show that the
stability of the self-trapped state of the hole drastically depends on the
amount of the exact exchange in the density functional: at less than 30% of the
Hartree-Fock exchange, only delocalized hole is stable, at 50% - both
delocalized and self-trapped states are stable, while further increase of exact
exchange results in only the self-trapped state being stable. We argue that the
main contributions to the self-trapping energy such as the kinetic energy of
the localizing charge, the chemical bond formation of the di-halogen quasi
molecule, and the lattice polarization, are represented incorrectly within the
Kohn-Sham (KS) based approaches.Comment: 6 figures, 1 tabl
CIRIR programs: drilling and research opportunities at the Rochechouart Impact Structure
International audienc
The Origin of Behavior
We propose a single evolutionary explanation for the origin of several behaviors that have been observed in organisms ranging from ants to human subjects, including risk-sensitive foraging, risk aversion, loss aversion, probability matching, randomization, and diversification. Given an initial population of individuals, each assigned a purely arbitrary behavior with respect to a binary choice problem, and assuming that offspring behave identically to their parents, only those behaviors linked to reproductive success will survive, and less reproductively successful behaviors will disappear at exponential rates. When the uncertainty in reproductive success is systematic, natural selection yields behaviors that may be individually sub-optimal but are optimal from the population perspective; when reproductive uncertainty is idiosyncratic, the individual and population perspectives coincide. This framework generates a surprisingly rich set of behaviors, and the simplicity and generality of our model suggest that these derived behaviors are primitive and nearly universal within and across species
Motor coordination problems in children and adolescents with ADHD rated by parents and teachers: effects of age and gender
Summary.
Objective. ADHD is frequently accompanied by motor coordination problems. However, the co-occurrence of poor motor performance has
received less attention in research than other coexisting problems in ADHD. The underlying mechanisms of this association
remain unclear. Therefore, we investigated the prevalence of motor coordination problems in a large sample of children with
ADHD, and the relationship between motor coordination problems and inattentive and hyperactive/impulsive symptoms. Furthermore,
we assessed whether the association between ADHD and motor coordination problems was comparable across ages and was similar
for both genders.
Method. We investigated 486 children with ADHD and 269 normal controls. Motor coordination problems were rated by parents (Developmental
Coordination Disorder Questionnaire) and teachers (Groningen Motor Observation Scale).
Results. Parents and teachers reported motor coordination problems in about one third of children with ADHD. Problems of fine and
gross motor skills, coordination skills and motor control were all related to inattentive rather than hyperactive/impulsive
symptoms. Relative to controls, motor coordination problems in ADHD were still present in teenagers according to parents;
the prevalence diminished somewhat according to teachers. Boys and girls with ADHD were comparably affected, but motor performance
in controls was better in girls than in boys.
Conclusions. Motor coordination problems were reported in one third of children with ADHD and affected both boys and girls. These problems
were also apparent in adolescents with ADHD. Clinicians treating children with ADHD should pay attention to co-occurring motor
coordination problems because of the high prevalence and the negative impact of motor coordination problems on daily life
Increased cardiovascular risk in rats with primary renal dysfunction; mediating role for vascular endothelial function
Primary chronic kidney disease is associated with high cardiovascular risk. However, the exact mechanisms behind this cardiorenal interaction remain unclear. We investigated the interaction between heart and kidneys in novel animal model for cardiorenal interaction. Normal Wistar rats and Munich Wistar Fromter rats, spontaneously developing renal dysfunction, were subjected to experimental myocardial infarction to induce cardiac dysfunction (CD) and combined cardiorenal dysfunction (CRD), respectively (N = 5–10). Twelve weeks later, cardiac- and renal parameters were evaluated. Cardiac, but not renal dysfunction was exaggerated in CRD. Accelerated cardiac dysfunction in CRD was indicated by decreased cardiac output (CD 109 ± 10 vs. CRD 79 ± 8 ml/min), diastolic dysfunction (E/e′) (CD 26 ± 2 vs. CRD 50 ± 5) and left ventricular overload (LVEDP CD 10.8 ± 2.8 vs. CRD 21.6 ± 1.7 mmHg). Congestion in CRD was confirmed by increased lung and atrial weights, as well as exaggerated right ventricular hypertrophy. Absence of accelerated renal dysfunction, measured by increased proteinuria, was supported by absence of additional focal glomerulosclerosis or further decline of renal blood flow in CRD. Only advanced peripheral endothelial dysfunction, as found in CRD, appeared to correlate with both renal and cardiac dysfunction parameters. Thus, proteinuric rats with myocardial infarction showed accelerated cardiac but not renal dysfunction. As parameters mimic the cardiorenal syndrome, these rats may provide a clinically relevant model to study increased cardiovascular risk due to renal dysfunction. Peripheral endothelial dysfunction was the only parameter that correlated with both renal and cardiac dysfunction, which may indicate a mediating role in cardiorenal interaction
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