Sun-induced fluorescence - a new probe of photosynthesis: First maps from the imaging spectrometer HyPlant.

Variations in photosynthesis still cause substantial uncertainties in predicting photosynthetic CO2 uptake rates and monitoring plant stress. Changes in actual photosynthesis that are not related to greenness of vegetation are difficult to measure by reflectance based optical remote sensing techniques. Several activities are underway to evaluate the sun-induced fluorescence signal on the ground and on a coarse spatial scale using space-borne imaging spectrometers. Intermediate-scale observations using airborne-based imaging spectroscopy, which are critical to bridge the existing gap between small-scale field studies and global observations, are still insufficient. Here we present the first validated maps of sun-induced fluorescence in that critical, intermediate spatial resolution, employing the novel airborne imaging spectrometer HyPlant. HyPlant has an unprecedented spectral resolution, which allows for the first time quantifying sun-induced fluorescence fluxes in physical units according to the Fraunhofer Line Depth Principle that exploits solar and atmospheric absorption bands. Maps of sun-induced fluorescence show a large spatial variability between different vegetation types, which complement classical remote sensing approaches. Different crop types largely differ in emitting fluorescence that additionally changes within the seasonal cycle and thus may be related to the seasonal activation and deactivation of the photosynthetic machinery. We argue that sun-induced fluorescence emission is related to two processes: (i) the total absorbed radiation by photosynthetically active chlorophyll; and (ii) the functional status of actual photosynthesis and vegetation stress.

Stability limits of n-nonane calculated from molecular dynamics interface simulations.

Based on molecular dynamics simulation of the vapor-liquid interface, the classical thermodynamic spinodal for n-nonane is estimated using an earlier developed method. The choice of n-nonane as investigated molecule originates from the question whether a deviation from the spherical symmetry of a molecule affects the prediction of the stability limit data. As a result, we find that the estimated stability limit data for n-nonane are consistent within the experimental data available for the homologous series of the n-alkanes. It turns out that the slight alignment of the molecules parallel to the interface reported in the literature does not affect the method of transferring interface properties to the bulk phase stability limit.

Field vaccination of sheep with a larval-specific antigen of the gastrointestinal nematode, Haemonchus contortus, confers significant protection against an experimental challenge infection.

The availability of effective vaccines would add a valuable tool to the management of gastrointestinal nematode infections in livestock. While some experimental vaccines have shown protection in laboratory trials, few have been tested in the field. In the present study, eight month old sheep kept on pasture were treated with anthelmintic 8 weeks before vaccination with a larval surface antigen of the nematode parasite, Haemonchus contortus, under a commercially acceptable protocol, i.e. 2 immunizations using a commercial adjuvant; they were then given a controlled challenge infection 4 weeks later in indoor pens. Vaccination of sheep with 4 increasing doses of antigen resulted in significant reductions of 61% and 27% in cumulative faecal egg counts in the two highest dose groups, and a 69% reduction in worm burden in the highest dose group. Blood loss, as determined by packed cell volume, was also significantly reduced in the highest dose group of sheep. One outlier sheep showed an unusual increase in egg count without a concomitant increase in worm burden compared to the control sheep, indicating a vaccine-induced stress response. Antigen-specific serum antibody levels steadily increased in sheep while on pasture and decreased when transported to indoor pens. No difference in antibody levels could be detected between vaccinated and unvaccinated sheep, but all showed increased antibody levels compared to uninfected control sheep kept in indoors pens for 2-3 months, suggesting sheep were sensitized to the larval antigen either from low dose pasture contamination or cross reaction with pasture-related antigens. The results of these studies confirm the protective properties of the larval surface antigen and its protective effect when vaccinations are performed in the field.

Influence of the carrier gas molar mass on the particle formation in a vapor phase.

The influence of the molar mass of a carrier gas on the formation of nanoparticles in the vapor phase is investigated. The function of the carrier gas atmosphere is the regulation of the particle temperature by collisions with the cluster surface. The aim of this work is to optimize the carrier gas in a simulation in order to mimic a large amount of carrier gas atoms by few gas atoms with effective parameters. In this context the efficiency of the heat exchange with the carrier gas depending on its molar mass is analyzed. As a result one finds for varying molar masses and unchanged interaction parameters a competition between the efficiency and the number of the collisions. For too small molar masses the energy exchange per collision is too small while for too high masses the carrier gas atoms become very slow, decreasing the number of collisions.

Development of an EAM potential for zinc and its application to the growth of nanoparticles.

In the context of the investigation of particle formation, a potential model by means of the embedded atom method is developed for the hexagonal close packed metal zinc. This type of model includes many-body interactions caused by delocalised electrons in metals. The effective core charge as function of the distance is calculated here by an integral over the electron distribution function rather than fitting it to experimental data. In addition, the dimer potential is included in the parameterisation because we focus on the formation of nanoparticles from the vapour phase. With this potential model, the growth of zinc clusters consisting of 125 to 1000 atoms is investigated, which takes place at elevated temperatures in a liquid-like cluster state. The growing clusters are embedded in an argon carrier gas atmosphere which regulates the cluster temperature. The average thermal expansion of the clusters and the different lattice constants are analysed. For the determination of the cluster structure, the common-neighbour analysis method is extended to hexagonal close packed surface structures. During growth, small clusters with less than approximately 60 atoms develop transient icosahedral structure before transforming into hexagonal close-packed structure. The surface of the clusters exhibits a transformation from planes with high surface energy to the most stable ones. Besides ambiguous surface structures the final clusters are almost completely in an hexagonal close packed structure.

The relation of interface properties and bulk phase stability: molecular dynamics simulations of carbon dioxide.

The limit of metastability, the so-called spinodal, is calculated for pure carbon dioxide by molecular dynamics simulation. The determination of the spinodal is based on properties of the liquid vapor interface using a recently developed method. This method relates the tangential pressure component through the vapor-liquid interface to the van der Waals loop in the two-phase region of the phase diagram. By application of the thermodynamic stability criteria, the location of the spinodal can be determined. The spinodal determined in this way is called interface spinodal here. Furthermore, the simulation provides equation of state properties in the complete metastable region of the phase diagram. The performance of different correlation equations for the density and the pressure tensor profiles with respect to the estimation of the spinodal is compared. It has been found that the interface spinodal coincides with the thermodynamic mean field spinodal within some reasonable deviation. Finally the influence of the size of the simulation box on the spinodal properties is investigated showing that the temperature-density spinodal data are independent of the interface thickness. Additional simulations using a Lennard-Jones fluid confirm these results over a range of 1.5 orders of magnitude for the systems size. A further result is that interface systems require a very long simulation time in order to obtain reliable results.

New model for the correlation of the surface tension based on friction theory.

A new correlation method for the surface tension of fluids is proposed, which is based on friction theory applied to the interface of a two-phase system. The substance properties enter the model by a regular equation of state. Here we derive the method and test it with the Lennard-Jones 12-6 fluid as the reference system using molecular dynamics simulations of the vapor-liquid interface in combination with a new Lennard-Jones 12-6 equation of state. Further correlations of experimental surface tension data based on the Peng-Robinson and the PC-SAFT equations of state are presented. As a result, we find that the method allows an accurate correlation of the surface tension of pure fluids.

Polymorphisms of the VDR gene are associated with presence of solar keratoses on the skin.

BACKGROUND: Vitamin D has a range of biological effects including antiproliferative functions that are mediated through its receptors, encoded by the VDR gene. OBJECTIVES: We investigated polymorphisms within the VDR gene for association with solar keratosis (SK), a biomarker for skin cancer, and examined interactions with skin phenotype. METHODS: Among participants of the community-based Nambour Skin Cancer Study, we genotyped 190 people with SKs and 190 without for ApaI, TaqI and FokI polymorphisms. RESULTS: We found a significant difference in genotype frequencies of the TaqI polymorphism between affected and unaffected populations (P = 0.008). The TT/tt genotype group was associated with a twofold increase in odds of being affected by one or more SK. Individuals with fair skin and the TT/tt genotype had about a sevenfold increase, whereas fair-skinned people with the Tt genotype had a fourfold increase in odds of being affected by SK. Individuals with the TT/tt genotype who were prone to burn and not tan on acute sun exposure had about a sixfold increase in odds of SK. Fair-skinned people with VDR-Apa AA/aa genotypes had about an eightfold increase in odds of being affected by SK compared with a fivefold increase in individuals with the Aa genotype and fair skin. CONCLUSIONS: The trend for homozygote genotypes to increase the odds of SK suggests that intermediate VDR activity is important in protection or that the heterodimer formed by a heterozygous genotype may have an altered binding potential. Overall, these analyses indicate that VDR may be important in SK development.

Argon nucleation: bringing together theory, simulations, and experiment.

We present an overview of the current status of experimental, theoretical, molecular dynamics (MD), and density functional theory (DFT) studies of argon vapor-to-liquid nucleation. Since the experimental temperature-supersaturation domain does not overlap with the corresponding MD and DFT domains, separate comparisons have been made: theory versus experiment and theory versus MD and DFT. Three general theoretical models are discussed: Classical nucleation theory (CNT), mean-field kinetic nucleation theory (MKNT), and extended modified liquid drop model-dynamical nucleation theory (EMLD-DNT). The comparisons are carried out for the area below the MKNT pseudospinodal line. The agreement for the nucleation rate between the nonclassical models and the MD simulations is very good--within 1-2 orders of magnitude--while the CNT deviates from simulations by about 3-5 orders of magnitude. Perfect agreement is demonstrated between DFT results and predictions of MKNT (within one order of magnitude), whereas CNT and EMLD-DNT show approximately the same deviation of about 3-5 orders of magnitude. At the same time the agreement between all theoretical models and experiment remains poor--4-8 orders of magnitude for MKNT, 12-14 orders for EMLD-DNT, and up to 26 orders for CNT. We discuss possible reasons for this discrepancy and the ways to carry out experiment and simulations within the common temperature-supersaturation domain in order to produce a unified picture of argon nucleation.

Estimation of the liquid-vapor spinodal from interfacial properties obtained from molecular dynamics and lattice Boltzmann simulations.

Interfacial pressure and density profiles are calculated from molecular dynamics and lattice Boltzmann simulations of a liquid film in equilibrium with its vapor. The set of local values of tangential pressure and density along an interface exhibits a van der Waals-type loop; starting from the stable vapor bulk phase one passes through metastable and unstable states to the stable liquid bulk phase. The minimum and maximum values of the profile of tangential pressure are related to the liquid and vapor spinodal states, respectively. The spinodal pressures turn out to be linearly related to the extreme values of the tangential pressure in the interface. The comparison with equations of state shows good agreement with the simulation results of the spinodals. In addition the properties of the metastable region are obtained. Based on this investigation a method is proposed for the estimation of the liquid spinodal from experimentally obtained interfacial properties. Estimations for water and helium are presented.

Homogeneous nucleation and growth in supersaturated zinc vapor investigated by molecular dynamics simulation.

Homogeneous nucleation and growth of zinc from supersaturated vapor are investigated by nonequilibrium molecular dynamics simulations in the temperature range from 400 to 800 K and for a supersaturation ranging from log S=2 to 11. Argon is added to the vapor phase as carrier gas to remove the latent heat from the forming zinc clusters. A new parametrization of the embedded atom method for zinc is employed for the interaction potential model. The simulation data are analyzed with respect to the nucleation rates and the critical cluster sizes by two different methods, namely, the threshold method of Yasuoka and Matsumoto [J. Chem. Phys. 109, 8451 (1998)] and the mean first passage time method for nucleation by Wedekind et al. [J. Chem. Phys. 126, 134103 (2007)]. The nucleation rates obtained by these methods differ approximately by one order of magnitude. Classical nucleation theory fails to describe the simulation data as well as the experimental data. The size of the critical cluster obtained by the mean first passage time method is significantly larger than that obtained from the nucleation theorem.

Molecular-dynamics simulation of argon nucleation from supersaturated vapor in the NVE ensemble.

The possibility to conduct simulations of homogeneous nucleation of argon from a supersaturated vapor phase using a microcanonical or NVE ensemble is evaluated (NVE: number of particles N, volume V, and energy E are constant). In order to initiate a phase separation kinetic energy is removed from the system in one step which transfers the system into a supersaturated state. After this temperature jump the simulation is continued in a NVE ensemble. The simulations are performed for different initial-state points and different temperature jumps. The cluster formation and growth over the course of the adiabatic simulations are analyzed. The progression of the temperature being related to the cluster size in NVE systems is traced. Also the influence of the size of the simulation system is investigated. For a certain range of low supersaturation a dynamic coexistence between two states has been found. Furthermore, the obtained nucleation rates are correlated with two simple functions. By applying the nucleation theorems to these functions the size and excess energy of the critical cluster are estimated. The results are consistent with other theoretical data and experimental data available in the literature.

Amiodarone in restoration and maintenance of sinus rhythm in patients with chronic atrial fibrillation after unsuccessful direct-current cardioversion.

BACKGROUND: When direct-current (DC) cardioversion is used, sinus rhythm can be restored, at least temporarily, in 80-90% of patients with atrial fibrillation. However, there is a small but significant group of patients with chronic atrial fibrillation in whom DC cardioversion has failed to restore sinus rhythm. The value of antiarrhythmic drug pretreatment before DC cardioversion is still controversial. HYPOTHESIS: The aim of our study was to assess (1) the effectiveness of repeat DC cardioversion in patients with chronic atrial fibrillation after pretreatment with amiodarone, and (2) the efficacy of amiodarone in maintaining sinus rhythm after repeat cardioversion. METHODS: Forty-nine patients with chronic atrial fibrillation after ineffective DC cardioversion were included in the study. Repeat DC cardioversion was performed after loading with oral amiodarone, 10-15 mg/kg body weight/day for a period necessary to achieve the cumulative dose of over 6.0 g. RESULTS: Spontaneous conversion to sinus rhythm during amiodarone pretreatment was achieved in 9 of 49 patients (18%). Direct-current cardioversion was performed in 39 patients and sinus rhythm was achieved in 23 of these patients (59%). Mean heart rate decreased from 95 beats/min before to 68 beats/min after DC cardioversion (p < 0.001). Systolic blood pressure significantly (p < 0.05) decreased from 126 +/- 23 to 108 +/- 25 mmHg. Complications occurring in four patients just after electroconversion were well tolerated and of short duration. After 12 months, 52% of patients maintained sinus rhythm on low dose (200 mg/day) amiodarone therapy. CONCLUSION: Pretreatment with amiodarone and repeat DC cardioversion allows for restoration of sinus rhythm in about 65% of patients with chronic atrial fibrillation after first ineffective DC cardioversion. Direct-current cardioversion can be performed safely with the use of standard precautions in patients who are receiving amiodarone. At 12 months' follow-up, more than 50% of patients maintain sinus rhythm on low-dose amiodarone after successful repeat cardioversion.

[P-wave ekg averaging technique--a new method of selecting patients with paroxysmal atrial fibrillation]. / Technika usredniania zalamka P ekg--nowa metoda wyodrebniania chorych z napadowym migotaniem przedsionków.

The aim of study was to assess the value of signal averaged ecg for detection of patients (pts) at risk for paroxysmal atrial fibrillation (paf). We examined three groups of pts: group I-41 pts with nonvalvular paf, group II-20 pts with hypertension and/or ischemic heart disease without paf and group 3-26 health persons, without organic heart disease. In all pts the signal-averaged electrocardiogram triggered by P waves was recorded. Seven parameters of the spatial magnitude of filtered P wave were measured. Significant difference between group I and group II or III was found in most parameters. Using the method of multidimensional variance analysis we constructed "the diagnostic vector" in multidimensional parameters space, which was used to determine patients belonging to group. Total percent of right decision was 85%. These findings suggest that pts at risk for paf could be detected while in sinus rhythm by using the P wave-triggered signal-averaged ecg.

[Influence of diabetes on the clinical course and hospital mortality of patients with recent myocardial infarction]. / Wplyw cukrzycy na przebieg kliniczny i smiertelnosc wewnatrzszpitalna chorych ze swiezym zawalem serca.

In group of 1026 patients with recent myocardial infarction (from program "Streptokinase in acute myocardial infarction"--patients below 70 years old, up to 12 hours from the onset of the symptoms) we analyzed the influence of diabetes on clinical course and hospital mortality. In this group were 77 patients with noninsulin-dependent diabetes (NIDDM), and 21 patients were insulin-dependent diabetes (IDDM). The risk factors of coronary heart disease and myocardial infarction in the past were significantly more often in patients with diabetes than in subjects without diabetes. In hospital mortality was significantly higher (p < 0.05) in group of patients with diabetes (17.3%) than in group without diabetes (9.5%). Reinfarction in the hospital period occurred significantly more often in diabetes group (p < 0.01). Congestive heart failure was observed in 50% patients with diabetes and in 32.3% cases without diabetes (p < 0.01), the left ventricle aneurysm occurred accordingly 9.8% i 5.2% (N.S.). Early ventricular fibrillation and atrio-ventricular blocks occurred with the same frequency in the both groups. We analyzed also the influence of thrombolytic therapy on clinical course in patients with diabetes proving the benefit of this treatment.

[Prognostic value of an early peak CK-MB in plasma of patients treated with streptokinase for acute myocardial infarction]. / Wartosc prognostyczna wczesnego szczytu aktywnosci CK-MB w surowicy u chorych leczonych streptokinaza w ostrym zawale serca.

111 patients below 70 years old, with the first acute myocardial infarctions, 6 hours since the pain occurred--have been treated with streptokinase i.v. In 102 patients we obtained full curve of CK-MB activity. Early peak of CK-MB activity < 15 hours after onset of symptoms we have observed in 59 patients, and late peak of CK-MB activity > 15 hours in 43 patients. There was not any significant statistics differences between early and late groups in frequency of: early ventricular fibrillation (< 48 hours), complex ventricular arrhythmia (in 21 day), heart failure and in-hospital mortality. 1 patient died in hospital in early group and in late group also died 1 patient. The follow-up period was from 10 to 48 months (av. 26 +/- 13). 100 patients left the hospital and the full informations we have obtained in 97 cases. No one died in that time. In the group with early peak CK-MB activity we observed more often the unstable angina and the new myocardial infarction (21%) than in the group with late peak of CK-MB activity (15%), but these differences were nonsignificant. In conclusion our results don't confirm that the early peak of CK-MB activity is the positive risk factor of unstable angina and the new myocardial infarction.

[Effect of coronary artery patency after myocardial infarction on ventricular late potentials]. / Wplyw droznosci tetnicy wiencowej, w której dorzeczu doszlo do zawalu serca na wystepowanie póznych potencjalów komorowych.

This study evaluated the relation between patency of the infarct related artery and the presence of ventricular late potentials (VLP) on the signal-averaged electrocardiogram (ECG). 44 patients (pts) after myocardial infarction (MI) (35 men, 9 women; mean age 50 years) were studied by coronary angiography. measurement of ejection fraction and signal-averaged ECG. The infarct-related artery was closed in 15 pts and open in 29 pts. There was no difference in age, previous MI and location of infarct between the two study groups. Thrombolytic therapy in acute stage of MI was significantly often (p less than 0.05) in pts with open (59%) than closed (13%). The incidence of VLP was significantly higher (p less than 0.05) in group of pts with closed (40%) than open artery (7%). These data indicate that patency of the infarct-related artery has a beneficial effect on the electrophysiologic substrate for serious ventricular arrhythmias.

[A method of averaged ECG signal does not identify patients with ventricular tachycardia in disorders of intraventricular conduction]. / Technika usredniania sygnalu EKG nie pozwala na wyodrebnienie chorych z czestoskurczem komorowym przy zaburzeniach przewodnictwa sródkomorowego.

Conduction defect are known to delay and fragment the ecg signal and may be expected to cause changes on the signal-averaged ecg that mimic ventricular late potentials. The aim of our study was to asses whether signal-averaged ECG (SAE) identify patients (pts) with sustained ventricular tachycardia (VT) after myocardial infarction (MI) who display right or left bundle branch block (RBBB or LBBB). We studied 23 pts with RBBB and 25 pts with LBBB. SEA was recorded with bidirectional filters at 25-250 HZ and 40-250 Hz using Simson method. The total filtered QRS duration (QRSd), root mean square voltage in the terminal 40ms of the QRS (RMS40) and low amplitude signal duration less than 40uV (LAS40)) were measured. Signal-averaged parameters with a filter at 25-250 Hz were: [table: see text] Signal-averaged parameters with a filter at 40-259 Hz were: [table: see text] In conclusion SAE parameters do not allow separation of pts with sustained VT from pts with RBBB or LBBB after MI. These data indicate that conduction defects have effects on signal-averaged ecg parameters and may result in masking of ventricular late potentials.

Value of the atrial signal-averaged electrocardiogram in identifying patients with paroxysmal atrial fibrillation.

Atrial signal-averaged electrocardiogram was compared between 25 patients with paroxysmal atrial fibrillation and 20 healthy persons without atrial arrhythmias (control). The duration time of the high frequency (50-250 Hz) P wave was significantly (P less than 0.01) prolonged in the groups of patients with paroxysmal atrial fibrillation compared with the control group (116 +/- 16.4 versus 92 +/- 8.1 msec). The diagnostic value of the duration of the high frequency P wave for identifying patients with paroxysmal atrial fibrillation was 104 msec. Using this criterion, a sensitivity of 76% and a specificity of 90% were achieved. Our observation has shown that the atrial signal-averaged electrocardiogram is a useful technique for identifying patients with paroxysmal atrial fibrillation.

[Clinical significance of mitral valve insufficiency detected by Doppler echocardiography in acute myocardial infarction]. / Znaczenie kliniczne niedomykalnosci mitralnej wykrywanej echokardiografia dopplerowska w swiezym zawale serca.

Doppler echocardiography revealed in the third week of the recent myocardial infarction a pattern of mitral insufficiency in 27 (36%) of the 75 patients studied. Mitral insufficiency was usually associated with the more severe clinical course of myocardial infarction, with more frequent supraventricular and ventricular arrhythmias, heart failure, and with more extensive infarction area, as compared with the patients without mitral failure. A decreased contractibility of the left ventricle wall (especially in patients with anterior myocardial infarction accompanied by mitral insufficiency and enlargement ventricular dimension) may suggest its role in the development of mitral insufficiency in myocardial infarction. The results show the need of Doppler echocardiography in recent myocardial infarction to detect patients with an increased risk.