Minimum size for a nanoscale temperature discriminator based on a thermochemical system.

What are the limits of size reduction for information processing devices based on chemical reactions? In this paper, we partially answer this question. We show that a thermochemical system can be used to design a discriminator of the parameters associated with oscillations of the ambient temperature. Depending on the amplitude and frequency of the oscillations, the system exhibits sharp transitions between different types of its time evolutions. This phenomenon can be used to discriminate between different parameter values describing the oscillating environment. We investigate the reliability of the thermochemical discriminator as a function of the number of molecules involved in the reactions. A stochastic model of chemical reactions and heat exchange with the neighborhood, in which the number of molecules explicitly appears, is introduced. For the selected values of the parameters, thermochemical discriminators operating with less than 10(5) molecules appear to be unreliable.

Reaction-diffusion approach to prevertebrae formation: effect of a local source of morphogen.

Periodic structure formation is an essential feature of embryonic development. Many models of this phenomenon, most of them based on time oscillations, have been proposed. However, temporal oscillations are not always observed during development and how a spatial periodic structure is formed still remains under question. We investigate a reaction-diffusion model, in which a Turing pattern develops without temporal oscillations, to assess its ability to account for the formation of prevertebrae. We propose a correspondence between the species of the reaction scheme and biologically relevant molecules known as morphogens. It is shown that the model satisfactorily reproduces experiments involving grafting of morphogen sources into the embryos. Using a master equation approach and the direct simulation Monte Carlo method, we examine the robustness of the results to internal fluctuations.

Particle dynamics simulations of Turing patterns.

The direct simulation Monte Carlo method is used to reproduce Turing patterns at the microscopic level in reaction-diffusion systems. In order to satisfy the basic condition for the development of such a spatial structure, we propose a model involving a solvent, which allows for disparate diffusivities of individual reactive species. One-dimensional structures are simulated in systems of various lengths. Simulation results agree with the macroscopic predictions obtained by integration of the reaction-diffusion equations. Additional effects due to internal fluctuations are observed, such as temporal transitions between structures of different wavelengths in a confined system. For a structure developing behind a propagating wave front, the fluctuations suppress the induction period and accelerate the formation of the Turing pattern. These results support the ability of reaction-diffusion models to robustly reproduce axial segmentation including the formation of early vertebrae or somites in noisy biological environments.

Microscopic simulations of supersonic and subsonic exothermic chemical wave fronts and transition to detonation.

We perform microscopic simulations using the direct simulation Monte Carlo approach to an exothermic chemical wave front of Fisher-Kolmogorov, Petrovsky, Piskunov-type in a one-dimensional gaseous medium. The results confirm the existence of a transition from a weak detonation or deflagration to a Chapman-Jouguet detonation wave, that we already investigated at the macroscopic scale [G. Dumazer et al., Phys. Rev. E 78, 016309 (2008)]. In the domain of weak detonation or deflagration, the discrepancy between the propagation speeds deduced from the simulations and the macroscopic balance equations of hydrodynamics is explained by two microscopic effects, the discretization of the variables, known as cutoff effect, and the departure from local equilibrium. Remarkably, the propagation speed of a Chapman-Jouguet detonation wave is not sensitive to these perturbations of microscopic origin.

Master equation for a chemical wave front with perturbation of local equilibrium.

In order to develop a stochastic description of gaseous reaction-diffusion systems, which includes a reaction-induced departure from local equilibrium, we derive a modified expression of the master equation from analytical calculations based on the Boltzmann equation. We apply the method to a chemical wave front of Fisher-Kolmogorov-Petrovsky-Piskunov type, whose propagation speed is known to be sensitive to small perturbations. The results of the modified master equation are compared successfully with microscopic simulations of the particle dynamics using the direct simulation Monte Carlo method. The modified master equation constitutes an efficient tool at the mesoscopic scale, which incorporates the nonequilibrium effect without need of determining the particle velocity distribution function.

Transition between an exothermic chemical wave front and a generic flame.

We consider the two classes of exothermic chemical wave fronts, propagating toward a stable or an unstable steady state. The hydrodynamic equations for stream velocity, temperature, and concentrations are solved numerically for increasing values of the reaction heat. For a critical value of the heat release, we find a transition between a chemical front, whose speed depends on the chemical dynamics, and a generic flame, whose speed is entirely determined by heat release. We derive an analytical expression of the flame speed from the invariants of the hydrodynamic equations. This result substantiates macroscopic approaches widely used in combustion, in which the chemical models include only simplified reaction mechanisms.

Forbidden interval of propagation speed for exothermic chemical fronts.

We consider the propagation of an exothermic chemical front toward an unstable steady state. The hydrodynamic equations are solved numerically for increasing values of the activation energy of the reaction which controls the reaction front speed. For a large speed, the marginal stability criterion of the isothermal case is recovered. For a small speed, we observe two well-separated traveling waves: a heat front is preceding the reaction front. We find analytically a forbidden speed interval where the hydrodynamical system does not admit stationary traveling solutions.

Highly compact fiber Fabry-Perot interferometer: A new instrument design.

This paper presents the design, construction, and characterization of a new optical-fiber-based, low-finesse Fabry-Perot interferometer with a simple cavity formed by two reflecting surfaces (the end of a cleaved optical fiber and a plane, reflecting counter-surface), for the continuous measurement of displacements of several nanometers to several tens of millimeters. No beam collimation or focusing optics are required, resulting in a displacement sensor that is extremely compact (optical fiber diameter 125 µm), is surprisingly tolerant of misalignment (more than 5°), and can be used over a very wide range of temperatures and environmental conditions, including ultra-high-vacuum. The displacement measurement is derived from interferometric phase measurements using an infrared laser source whose wavelength is modulated sinusoidally at a frequency f. The phase signal is in turn derived from changes in the amplitudes of demodulated signals, at both the modulation frequency, f, and its harmonic at 2f, coming from a photodetector that is monitoring light intensity reflected back from the cavity as the cavity length changes. Simple quadrature detection results in phase errors corresponding to displacement errors of up to 25 nm, but by using compensation algorithms discussed in this paper, these inherent non-linearities can be reduced to below 3 nm. In addition, wavelength sweep capability enables measurement of the absolute surface separation. This experimental design creates a unique set of displacement measuring capabilities not previously combined in a single interferometer.

Multiple Pit-1-binding sites facilitate estrogen responsiveness of the prolactin gene.

Previous studies have shown that estrogen responsiveness of the rat PRL gene requires the presence of both the estrogen receptor and the tissue-specific transcription factor, Pit-1. To examine the contribution of individual Pit-1-binding sites in permitting an estrogen response, we mutated specific sites in both the proximal and distal regions of the rat PRL gene. The studies reveal that mutation of Pit-1-binding sites in either the proximal or the distal region can have an effect on estrogen responsiveness. The most important Pit-1-binding site appears to be the site in the distal enhancer, which is adjacent to the estrogen receptor-binding site. However, mutation of combinations of other Pit-1-binding sites reveals that these sites also contribute to the estrogen response of the PRL gene. The binding sequences for another transcription factor cannot substitute for Pit-1 sites in bringing about a wild-type estrogen response, as shown by replacement of Pit-1-binding sites with a consensus cAMP-responsive element. Conversion of the imperfect palindromic estrogen response element of the PRL gene to a perfect palindrome eliminated the positive effects of an intact 1D Pit-1-binding site. To examine potential physical interactions between the estrogen receptor and Pit-1, a protein interaction assay was performed. The results demonstrate that labeled estrogen receptor can bind to Pit-1 immobilized on glutathione agarose beads. However, most of the interaction between Pit-1 and the estrogen receptor appears to be DNA dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of DNA regions mediating the ability of Ca2+/calmodulin dependent protein kinase II to stimulate prolactin promoter activity.

The ability of Ca2+/calmodulin-dependent protein kinases (CaMKs) to regulate transcription of the rat prolactin (PRL) gene has been examined. We found that KN-62, a potent inhibitor of CaM kinases, blunted the ability of TRH to activate the prolactin promoter. Transfection experiments using expression plasmids for constitutively active forms of CaMKI, CaMKII, or CaMKIV show that CaMKII is the most effective activator of prolactin promoter expression. Deletion studies demonstrated that the upstream boundary of sequences necessary to respond to CaMKII is located within the distal enhancer of the prolactin gene. Neither the distal enhancer alone nor the proximal region of the prolactin gene are sufficient to mediate a response to CaMKII. Mutational analysis suggests that several Pit-1 binding sites contribute to CaMKII responsiveness. These findings suggest that CaMKII responsiveness of the prolactin promoter requires multiple factor binding sites in both the distal and proximal regions of the gene.

Respiratory symptoms and farming practices in farmers associated with an acute febrile illness after organic dust exposure.

STUDY OBJECTIVE: To conduct a preliminary study of occupational respiratory complaints in farmers who have experienced organic dust toxic syndrome (ODTS) symptoms. DESIGN: Cross-sectional. SETTING: An agricultural trade show. INTERVENTION: None. MEASUREMENT AND RESULTS: Two hundred ninety-seven people (204 men, 93 women) completed a questionnaire about agricultural practices, respiratory health (including history of febrile episodes while handling grain), and use of respirators. Spirometry was also performed. ODTS symptoms were described by 107 of the people (36%). A strong significant association was found between ODTS and cough or chest tightness after handling grain (odds ratio [OR], 7.5; 95% confidence ratio [CI], 4.2 to 13.5). People who experienced cough or chest tightness after handling grain were more likely to report handling grain sorghum than people who had not experienced cough or chest tightening after handling grain (OR, 2.1; 95% CI, 1.3 to 3.5). The strong association seen between ODTS and frequent use of a respirator while working in grain bins (OR, 3.9; 95% CI, 1.6 to 9.4) may indicate that farmers began using respirators after respiratory symptoms developed. CONCLUSIONS: Having a history consistent with ODTS exposure was very common in the farmers surveyed. Farmers who had a history consistent with ODTS were more likely to report cough or chest tightness with handling grain. Exposure to grain sorghum was more likely to be associated with respiratory symptoms than was exposure to other types of grain. There is a need for additional studies to further examine the relationship between ODTS and respiratory symptoms with grain dust exposure in farmers.

Sensitivity of explosion to departure from partial equilibrium.

We study a thermochemical gaseous system in the vicinity of the bifurcation related to the emergence of bistability. Corrections to the standard deterministic dynamics induced by the perturbation of the particle velocity distribution are obtained from the solution of the Boltzmann equation. Using these results, analytical expressions including the nonequilibrium effects are derived for the ignition time in the explosive regime and mean first passage time in the bistable regime. It is demonstrated that a departure from partial equilibrium can shift the bifurcation point. The system which was bistable according to the standard deterministic approach, can become monostable and explosive in the presence of nonequilibrium effects. Even when the system remains in the bistable regime, the mean first passage time can be changed by several orders of magnitude. In the monostable domain, the ignition time can be about ten times smaller than the unperturbed value. These analytical predictions agree well with the results of the microscopic simulations of the dilute gas system.

Stochastic effects in a thermochemical system with Newtonian heat exchange.

We develop a mesoscopic description of stochastic effects in the Newtonian heat exchange between a diluted gas system and a thermostat. We explicitly study the homogeneous Semenov model involving a thermochemical reaction and neglecting consumption of reactants. The master equation includes a transition rate for the thermal transfer process, which is derived on the basis of the statistics for inelastic collisions between gas particles and walls of the thermostat. The main assumption is that the perturbation of the Maxwellian particle velocity distribution can be neglected. The transition function for the thermal process admits a continuous spectrum of temperature changes, and consequently, the master equation has a complicated integro-differential form. We perform Monte Carlo simulations based on this equation to study the stochastic effects in the Semenov system in the explosive regime. The dispersion of ignition times is calculated as a function of system size. For sufficiently small systems, the probability distribution of temperature displays transient bimodality during the ignition period. The results of the stochastic description are successfully compared with those of direct simulations of microscopic particle dynamics.

[Comparison of the occurrence of symptoms during hospitalization in perimenopausal and postmenopausal women with various pathological conditions of the endometrium]. / Porównanie czestosci wystepowania objawów stanowiacych powód hospitalizacji kobiet w wieku okolo i pomenopauzalnym, w róznych stanach patologii blony sluzowej macicy.

The aim of the study was to investigate the incidence and risk factors for endometrial adenocarcinoma which are associated with abnormal bleeding patterns, overweight, a lower number of deliveries and a later menopause, diabetes mellitus and hypertension. A retrospective study (from 1990 to 1993) of 2887 women with pathological gynecological signs and symptoms was performed. Risk factors such as age, weight, height, Brock index, age of menopause, diabetes mellitus and hypertension, stage and cell type were analysed. The patients were between 38 to 84 years old (average 53.9 +/- 10.2). They were divided into two subgroups: 259 patients below 84 years of age with histologically confirmed neoplasm and 2628 women hospitalised due to gynecological signs and symptoms which were not, however, diagnosed as neoplastic disorders. It was shown that overweight woman in sixth life decade with a lower number of deliveries and a later menopause had a higher risk of endometrial cancer.

[Evaluation of risk factors for endometrial adenocarcinoma in women with diabetes, hypertension and obesity hospitalized for pathologic uterine hemorrhage around the age of postmenopause]. / Ocena ryzyka powstania raka blony sluzowej macicy u kobiet z cukrzyca, nadcisnieniem i otyloscia, hospitalizowanych z powodu patologicznych krwawien z macicy, w wieku okolo-i pomenopauzalnym.

The aim of the study was to investigate the incidence and risk factors for endometrial adenocarcinoma which are associated with abnormal bleeding patterns, overweight, a lower number of deliveries and a later menopause, diabetes mellitus and hypertension. A retrospective study (from 1991 to 1993) of 2887 women with pathological gynecological sings and symptoms was performed. Risk factors such as age, height, weight, Brock index, age of menopause, diabetes mellitus and hypertension, stage and cell type were analyzed. The patients were between 38 to 35 years old (average 53.9 +/- 10.2). They were divided into two subgroups: 259 patients below 85 years of age with a histologically confirmed neoplasm, and 2628 women hospitalised due to gynecological signs and symptoms which were not, however, diagnosed as neoplastic disorders. However, it is necessary to note the relationship between the typical age for these two characteristics and the typical age for endometrial cancer. Diabetes was found to be a strong factor whereas hypertension appears to be a relatively weak one for endometrial carcinoma. High Brock's index is also associated with ab increased risk of endometrial carcinoma.

[Statistical methods applied in retrospective risk assessment of endometrial adenocarcinoma occurrence]. / Metody statystyczne stosowane w retrospektywnej ocenie ryzyka wystapienia raka blony sluzowej macicy.

A retrospective study about frequency of occurrence of endometrial adenocarcinoma in postmenopausal women which are associated with diabetes mellitus, overweight and hypertension was performed. The aim of the study was to have risk factors for carcinoma of endometrium estimated. The nonparametric statistics such as: 2 x 2 table chi 2/Phi2 test, observed versus expected chi 2 test and estimation of relative risk were applicable. A retrospective study (from 1991 to 1993) of 2887 patients of Institute of Obstetrics and Gynecology University School of Poznan with pathological sign and symptoms was performed.

[A case of IUD translocation to the peritoneal cavity--diagnostic procedures and treatment]. / Przypadek translokacji IUD do jamy otrzewnej--postepowanie diagnostyczno terapeutyczne.

The case of Cooper-T IUD translocation to peritoneal cavity diagnosed 5 years after its insertion is presented. Authors show diagnostic problems resulting from non typical complaints and incomplete documentation.

[Treatment of ureter injuries after obstetric-gynecologic surgery]. / Leczenie uszkodzen moczowodu po operacjach ginekologiczno-polozniczych.

The article presents an analysis of 21 patients with ureter injuries originated during obstetric-gynaecological operations treated in Urology Clinic in Medical Academy Poznan. Attention was particularly focused on prevention and fast diagnosis of injuries based on intra-operation examination usg, urography, and ascending pyelography. This fast diagnosis is of crucial importance for the cure.

Temperature-driven coherence resonance and stochastic resonance in a thermochemical system.

We perform the stochastic analysis of a thermochemical system using a master equation which describes a chemical reaction and includes discrete and continuous temperature jumps. We study the time evolution of the system selecting the temperature of the thermostat as an easily tunable control parameter. Depending on the thermostat temperature, the system can be in an excitable, oscillatory, or stationary regime. Stochastic time series for the system temperature are generated and the distributions of interspike intervals are analyzed in the three dynamical regimes separated by a homoclinic bifurcation and a Hopf bifurcation. Different constructive roles of internal fluctuations are exhibited. A noise-induced transition is observed in the vicinity of the Hopf bifurcation. Coherence resonance and stochastic resonance are found in the oscillatory regime. In a range of thermostat temperatures, a nontrivial behavior of the highly nonlinear system is revealed by the existence of both a minimum and a maximum in the scaled standard deviation of interspike intervals as a function of particle number. This high sensitivity to system size illustrates that controlling dynamics in nanoreactors may remain a difficult task.

Development of a precision nanoindentation platform.

The design, construction, and performance of a surface-referenced nanoindentation instrument, termed a precision nanoindentation platform (PNP), are presented. The PNP is a symmetrically designed instrument with a centrally located indenter tip attached to a force cell for measuring the forces between the tip and a specimen. Penetration of the indenter tip into the specimen surface is measured using two proximity sensors placed symmetrically about the indenter. Each proximity sensor is attached to a piezoelectric actuator that is servo controlled to maintain the sensor and the reference frame to which it is attached at a constant height relative to the specimen surface. As the indenter tip penetrates the specimen surface, the movement of the tip relative to the two surface reference frames is measured using capacitance gauges and the average of these displacements is used as a measure of penetration depth. The current indenter is capable of applying indentation forces of up to 150 mN with a noise floor below 2 µN rms for a sampling rate of 1 kHz, and measuring displacement with 0.4 nm rms noise for the same sampling rate. The proximity sensors are capable of maintaining surface height variations of less than 1.0 nm with penetration depths of up to 10 µm. Long-term stability tests indicate a total uncertainty in indentation depth less than 10 nm for periods as long as 12 h. To demonstrate instrument accuracy, repeated indention cycles were performed on a fused silica specimen using incrementally increasing indention force. From this test, an average value of 72 GPa ± 1.5 GPa for the Young's modulus was obtained from the elastic unloading curves for 10 measurements ranging in maximum force from 5 mN to 50 mN. To demonstrate longer-term instrument stability, a poly(methyl methacrylate) specimen was subjected to a fixed 5 mN indentation force for 4 h; two distinct creep-like mechanisms were observed.