Hydrosilylation of Olefins Activated on Highly Lewis-Acidic Calcium Cation.

The report introduces simple yet highly reactive calcium salt, Ca[Al(ORF)4]2 (RF=C(CF3)3), 1, which effectively catalyses olefin hydrosilylation through an unusual mechanism involving the activation of the alkene molecule. Upon dissolution in o-difluorobenzene (oDFB), 1 forms a highly Lewis acidic [Ca(oDFB)6]2+ complex. Our DFT calculations reveal that fluoride ion affinity is comparable to SbF5. Reactivity tests show that it effectively catalyses the hydrosilylation of olefins with high regioselectivity, also in reactions involving sterically demanding substrates like (iPr)3SiH or tetrasubstituted olefins. Experimental and computational results point to the mechanism where the olefin molecule forms a complex with Ca2+, which significantly facilitates the attack of H-SiR3 on the C=C double bond.

The role of mindfulness in physical activity: a systematic review.

Despite continued public health campaigns to promote physical activity, a majority of the population is inactive. In recent years, mindfulness-based approaches have been used in health and lifestyle interventions for physical activity promotion. We conducted a systematic literature review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to investigate the evidence for the potential of mindfulness-based approaches for physical activity. We searched electronic databases for papers that met eligibility criteria and identified 40 studies for inclusion. Evidence from cross-sectional studies (n = 20) indicated a positive relationship between dispositional mindfulness and physical activity, particularly with psychological factors related to physical activity. Five studies found that the mindfulness-physical activity relationship was mediated by stress, psychological flexibility, negative affect and shame, satisfaction and state mindfulness. Evidence from mindfulness-based interventions (n = 20) suggested positive between-subjects effects on physical activity, but interventions varied in duration, session length, group size, delivery, content and follow-up. Mindfulness-based interventions were more likely to be successful if they were physical activity-specific and targeted psychological factors related to physical activity. The body of research shows a need for more methodologically rigorous studies to establish the effect of mindfulness on physical activity and to identify potential mechanisms involved in the mindfulness-physical activity relationship reliably.

Dobutamine stress echocardiography in the diagnosis of asymptomatic ischemic heart disease in patients with chronic kidney disease--review of literature and single-center experience.

BACKGROUND: Coronary artery disease (CAD) may be present in kidney transplant (KT) candidates without the presence of CAD clinical symptoms. This study joins an ongoing discussion about appropriate noninvasive diagnostic approaches for ischemic heart disease (IHD) assessment and patient selection for revascularization procedures. The aim of this study was to evaluate the role of dobutamine stress echocardiography (DSE) in IHD diagnosis in initially asymptomatic maintenance hemodialysis (HD) patients. METHODS: Forty HD patients aged 52.4 ± 2.0 years, were studied for 2.5 years. At inclusion, they were free of both symptoms and history of IHD. Standard electrocardiography (ECG), chest X-ray, standard echocardiography, DSE, 24-hour Holter ECG, and Doppler ultrasonography (carotids and lower extremities) were performed. Results were analyzed according to a predefined diagnostic algorithm. RESULTS: DSE yielded negative results in all patients. Left ventricular (LV) ejection fraction ≤ 60%, LV hypertrophy, and Holter ECG silent ischemia features were noticed in 15%, 70%, and 10% of patients, respectively. Atherosclerotic lesions in lower extremities and carotid arteries were present in 50% and 37.5% of patients, respectively. During the follow-up, 9/40 patients died, including 6 cardiovascular (CV) deaths: 2 with intermediate and 4 with high CV risk according to the proposed algorithm. CONCLUSIONS: In asymptomatic KT candidates, not only DSE, but also other noninvasive tests (eg, echocardiography and Doppler ultrasonography of the carotid and peripheral arteries) along with a detailed profile of the remaining CV risk factors should be performed and analyzed. Defined composition of risk factors and particular changes in noninvasive tests may be an indication for coronary angiography.

Two-dimensional EPR imaging with the rapid scan and rotated magnetic field gradient.

A new method for fast 2D Electron Paramagnetic Resonance Imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradient, whose orientation is changed at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples. The images from the acquired data are reconstructed using iterative algorithms. The proposed method allows to reduce the image acquisition time up to 10 ms for 2D EPRI, and to detect the sinogram with infinitesimal angular step between projections.

Two-dimensional spectral-spatial EPR imaging with the rapid scan and modulated magnetic field gradient.

A new method for fast spectral-spatial electron paramagnetic resonance imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradients, whose amplitude is modulated at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples. The spectral-spatial images from the acquired data are reconstructed using iterative algorithms. The proposed method allows to acquire the spectral-spatial image with 800 projections at 200ms.

Feature-selective attention enhances color signals in early visual areas of the human brain.

We used an electrophysiological measure of selective stimulus processing (the steady-state visual evoked potential, SSVEP) to investigate feature-specific attention to color cues. Subjects viewed a display consisting of spatially intermingled red and blue dots that continually shifted their positions at random. The red and blue dots flickered at different frequencies and thereby elicited distinguishable SSVEP signals in the visual cortex. Paying attention selectively to either the red or blue dot population produced an enhanced amplitude of its frequency-tagged SSVEP, which was localized by source modeling to early levels of the visual cortex. A control experiment showed that this selection was based on color rather than flicker frequency cues. This signal amplification of attended color items provides an empirical basis for the rapid identification of feature conjunctions during visual search, as proposed by "guided search" models.

Towards benchmark second-order correlation energies for large atoms: Zn2+ revisited.

To provide very accurate reference results for the second-order Møller-Plesset (MP2) energy and its various components for Zn(2+), which plays for 3d-electron systems a similar role as Ne for smaller atoms and molecules, we have performed extensive calculation by two completely different implementations of the MP2 method: the finite element method (FEM) and the variation-perturbation (VP) method. The FEM and VP calculations yield partial wave contributions up to l(max)=45 and 12, respectively. Detailed comparison of all FEM and VP energy components for l(max)=12 has disclosed an extraordinary similarity, which justifies using the present results as benchmarks. The present correlation energies are compared with other works. The dependability of an earlier version of FEM, already applied to very large closed-shell atoms, is confirmed. It has been found that for larger atoms the accuracy of the analytical Hartree-Fock results has an impact on the accuracy of the MP2 energies greater than for smaller atoms. Fields of applications of the present results in studies of various electron correlation effects in 3d-electron atoms and molecules are indicated.

Sustained division of the attentional spotlight.

By voluntarily directing attention to a specific region of a visual scene, we can improve our perception of stimuli at that location. This ability to focus attention upon specific zones of the visual field has been described metaphorically as a moveable spotlight or zoom lens that facilitates the processing of stimuli within its 'beam'. A long-standing controversy has centred on the question of whether the spotlight of spatial attention has a unitary beam or whether it can be divided flexibly to disparate locations. Evidence supporting the unitary spotlight view has come from numerous behavioural and electrophysiological studies. Recent experiments, however, indicate that the spotlight of spatial attention may be divided between non-contiguous zones of the visual field for very brief stimulus exposures (&<100 ms). Here we use an electrophysiological measure of attentional allocation (the steady-state visual evoked potential) to show that the spotlight may be divided between spatially separated locations (excluding interposed locations) over more extended time periods. This spotlight division appears to be accomplished at an early stage of visual-cortical processing.

The effect of familiarity on visual-search performance: evidence for learned basic features.

In this study, the effects of familiarity on visual search were investigated. To avoid any confounding between familiarity and visual-feature differences between item pairs, Ns and mirror-Ns were presented as target and as distractors to a group of German participants and to a group of Slavic participants. For the Germans only N was familiar, whereas for the Slavs both N and mirror-N were familiar. The results show that search was difficult only when the Germans had to find an N among mirror-Ns. In any other case, search was efficient. Therefore, our results demonstrate that, contrary to earlier suggestions, search for a familiar item among familiar distractors can be easy. This supports the hypothesis that familiarity improves distractor grouping. However, the data are also compatible with the idea that letters are standard or basic features, which implies that basic features can be learned.

How to produce an absent-advantage in visual search.

In a series of four experiments, we investigated the conditions under which target-absent responses are faster than target-present responses in visual search. Previous experiments have shown that such an absent-advantage occurs mainly for homogeneous distractors arranged in a regular pattern. From these results, it has been concluded that the absent-advantage is due to perceptual processes, such as grouping by similarity. Our data show that such processes are not sufficient. Rather, the absent-advantage is the result of interactions between perceptual and decisional processes. Certain perceptual conditions, such as randomizing stimulus patterns, lead to specific criteria settings that produce an absent-advantage. That such an account can explain our main results is demonstrated by modeling our data with a modified version of the Guided Search 2 model.

[Treatment of external postoperative fistulas of the gastrointestinal tract]. / Leczenie zewnetrznych pooperacyjnych przetok przewodu pokarmowego.

In the years 1985-1996 82 patients with postoperative external fistulas of gastrointestinal tract (pefgt) were treated in the Department of General Surgery of Hospital in Olsztyn. The age of the patient varied from 18 to 70 years. 37 patients were women and 45 man. Volume of excreted fluid fluctuated from 100 ml to 3000 ml per day. The most frequent cause of pefgt was dehiscence of the anastomosis of jejunum in 31 patients, and operations of complications of gastric or duodenal ulcer disease in 30 patients. 54 patients underwent medical treatment. It was based on compensation of disorders in water and electrolyte balance and acid-base equilibrium, nutritional treatment, protection of the skin, suction of the excreted fluid, controlling of foci of infection, rehabilitation. 7 patients were reoperated for the purpose of closing the fistula and 21 to drain abscess or to stop bleeding. 57 (70%) out of 82 patients recovered, 25 (30%) died. In this number 14 patients among 54 treated conservatively and 11 out from 28 operated. The most frequent cause of death was sepsis (15 patients). The conservative treatment including TPN is successful in majority of patients with pefgt and indispensable in patients treated operatively. Special attention should be given for coexisting intraperitoneal abscessa, peritonitis and sepsis.