Algorithmic Statistics

While Kolmogorov complexity is the accepted absolute measure of information content of an individual finite object, a similarly absolute notion is needed for the relation between an individual data sample and an individual model summarizing the information in the data, for example, a finite set (or probability distribution) where the data sample typically came from. The statistical theory based on such relations between individual objects can be called algorithmic statistics, in contrast to classical statistical theory that deals with relations between probabilistic ensembles. We develop the algorithmic theory of statistic, sufficient statistic, and minimal sufficient statistic. This theory is based on two-part codes consisting of the code for the statistic (the model summarizing the regularity, the meaningful information, in the data) and the model-to-data code. In contrast to the situation in probabilistic statistical theory, the algorithmic relation of (minimal) sufficiency is an absolute relation between the individual model and the individual data sample. We distinguish implicit and explicit descriptions of the models. We give characterizations of algorithmic (Kolmogorov) minimal sufficient statistic for all data samples for both description modes--in the explicit mode under some constraints. We also strengthen and elaborate earlier results on the ``Kolmogorov structure function'' and ``absolutely non-stochastic objects''--those rare objects for which the simplest models that summarize their relevant information (minimal sufficient statistics) are at least as complex as the objects themselves. We demonstrate a close relation between the probabilistic notions and the algorithmic ones.Comment: LaTeX, 22 pages, 1 figure, with correction to the published journal versio

Anelastic sensitivity kernels with parsimonious storage for adjoint tomography and full waveform inversion

We introduce a technique to compute exact anelastic sensitivity kernels in the time domain using parsimonious disk storage. The method is based on a reordering of the time loop of time-domain forward/adjoint wave propagation solvers combined with the use of a memory buffer. It avoids instabilities that occur when time-reversing dissipative wave propagation simulations. The total number of required time steps is unchanged compared to usual acoustic or elastic approaches. The cost is reduced by a factor of 4/3 compared to the case in which anelasticity is partially accounted for by accommodating the effects of physical dispersion. We validate our technique by performing a test in which we compare the $K_\alpha$ sensitivity kernel to the exact kernel obtained by saving the entire forward calculation. This benchmark confirms that our approach is also exact. We illustrate the importance of including full attenuation in the calculation of sensitivity kernels by showing significant differences with physical-dispersion-only kernels

Changes in the quality of doctor–patient communication between 1982 and 2001: an observational study on hypertension care as perceived by patients and general practitioners

Background: The rise of evidence-based medicine may have implications for the doctor–patient interaction. In recent decades, a shift towards a more task-oriented approach in general practice indicates a development towards more standardised healthcare. Objective: To examine whether this shift is accompanied by changes in perceived quality of doctor–patient communication. Design: GP observers and patient observers performed quality assessments of Dutch General Practice consultations on hypertension videotaped in 1982–1984 and 2000–2001. In the first cohort (1982–1984) 81 patients were recorded by 23 GPs and in the second cohort (2000–2001) 108 patients were recorded by 108 GPs. The GP observers and patient observers rated the consultations on a scale from 1 to 10 on three quality dimensions: medical technical quality, psychosocial quality and quality of interpersonal behaviour. Multilevel regression analyses were used to test whether a change occurred over time. Results: The findings showed a significant improvement over time on all three dimensions. There was no difference between the quality assessments of GP observers and patient observers. The three different dimensions were moderately to highly correlated and the assessments of GP observers showed less variability in the second cohort. Conclusions: hypertension consultations in general practice in the Netherlands received higher quality assessments by general practitioners and patients on medical technical quality, psychosocial quality and the quality of interpersonal behaviour in 2000–2001 as compared with the 1980s. The shift towards a more task-oriented approach in hypertension consultations does not seem to detract from individual attention for the patient. In addition, there is less variation between general practitioners in the quality assessments of more recent consultations. The next step in this line of research is to unravel the factors that determine patients' quality assessments of doctor–patient communication. (aut.ref.

Simulations of Ground Motion in the Los Angeles Basin Based upon the Spectral-Element Method

We use the spectral-element method to simulate ground motion generated by two recent and well-recorded small earthquakes in the Los Angeles basin. Simulations are performed using a new sedimentary basin model that is constrained by hundreds of petroleum-industry well logs and more than 20,000 km of seismic reflection profiles. The numerical simulations account for 3D variations of seismic-wave speeds and density, topography and bathymetry, and attenuation. Simulations for the 9 September 2001 M_w 4.2 Hollywood earthquake and the 3 September 2002 M_w 4.2 Yorba Linda earthquake demonstrate that the combination of a detailed sedimentary basin model and an accurate numerical technique facilitates the simulation of ground motion at periods of 2 sec and longer inside the basin model and 6 sec and longer in the regional model. Peak ground displacement, velocity, and acceleration maps illustrate that significant amplification occurs in the basin

Женский роман в гендерной перспективе

В статье излагаются результаты анализа становления и развития англо- и немецкоязычного женского романа – от канонического, через эмансипированный, к постфеминистскому, – в связи с широким распространением идей феминизма и опирающихся на них гендерных исследований.У статті представлено результати аналізу становлення й розвитку англо- та німецько-мовного жіночого роману – від канонічного, через емансипований до постфеміністського, – у його зв'язку з широким розповсюдженням ідей фемінізму та породженими останнім гендерними дослідженнями.The article offers the results of the author's analysis of Romance in the USA, UK and Germany, following its development from the Canon, through the Emancipated, to the present-day Post-feminist, all stages connected with and influenced by the growth of the ideas of feminism and Gender Studies

Inflammation-induced hepcidin-25 is associated with the development of anemia in septic patients: an observational study

Contains fulltext : 98009.pdf (publisher's version ) (Open Access)INTRODUCTION: Anemia is a frequently encountered problem during inflammation. Hepcidin is an interleukin-6 (IL-6)-induced key modulator of inflammation-associated anemia. Human sepsis is a prototypical inflammatory syndrome, often complicated by the development of anemia. However, the association between inflammation, hepcidin release and anemia has not been demonstrated in this group of patients. Therefore, we explored the association between hepcidin and sepsis-associated anemia. METHODS: 92 consecutive patients were enrolled after presentation on the emergency ward of a university hospital with sepsis, indicated by the presence of a proven or suspected infection and >/= 2 extended systemic inflammatory response syndrome (SIRS) criteria. Blood was drawn at day 1, 2 and 3 after admission for the measurement of IL-6 and hepcidin-25. IL-6 levels were correlated with hepcidin concentrations. Hemoglobin levels and data of blood transfusions during 14 days after hospitalisation were retrieved and the rate of hemoglobin decrease was correlated to hepcidin levels. RESULTS: 53 men and 39 women with a mean age of 53.3 +/- 1.8 yrs were included. Hepcidin levels were highest at admission (median[IQR]): 17.9[10.1 to 28.4]nmol/l and decreased to normal levels in most patients within 3 days (9.5[3.4 to 17.9]nmol/l). Hepcidin levels increased with the number of extended SIRS criteria (P = 0.0005). Highest IL-6 levels were measured at admission (125.0[46.3 to 330.0]pg/ml) and log-transformed IL-6 levels significantly correlated with hepcidin levels at admission (r = 0.28, P = 0.015), day 2 (r = 0.51, P < 0.0001) and day 3 (r = 0.46, P < 0.0001). Twelve patients received one or more blood transfusions during the first 2 weeks of admission, not related to active bleeding. These patients had borderline significant higher hepcidin level at admission compared to non-transfused patients (26.9[17.2 to 53.9] vs 17.9[9.9 to 28.8]nmol/l, P = 0.052). IL-6 concentrations did not differ between both groups. Correlation analyses showed significant associations between hepcidin levels on day 2 and 3 and the rate of decrease in hemoglobin (Spearman's r ranging from -0.32, P = 0.03 to -0.37, P = 0.016, respectively). CONCLUSIONS: These data suggest that hepcidin-25 may be an important modulator of anemia in septic patients with systemic inflammation