Linearization of Cohomology-free Vector Fields

We study the cohomological equation for a smooth vector field on a compact manifold. We show that if the vector field is cohomology free, then it can be embedded continuously in a linear flow on an Abelian group

Theoretical prediction of spectral and optical properties of bacteriochlorophylls in thermally disordered LH2 antenna complexes

A general approach for calculating spectral and optical properties of pigment-protein complexes of known atomic structure is presented. The method, that combines molecular dynamics simulations, quantum chemistry calculations and statistical mechanical modeling, is demonstrated by calculating the absorption and circular dichroism spectra of the B800-B850 BChls of the LH2 antenna complex from Rs. molischianum at room temperature. The calculated spectra are found to be in good agreement with the available experimental results. The calculations reveal that the broadening of the B800 band is mainly caused by the interactions with the polar protein environment, while the broadening of the B850 band is due to the excitonic interactions. Since it contains no fitting parameters, in principle, the proposed method can be used to predict optical spectra of arbitrary pigment-protein complexes of known structure.Comment: ReVTeX4, 11 pages, 9 figures, submitted to J. Chem. Phy

Correlation analysis of focal brain changes and brain atrophy with cognitive impairment in MS patients

Multipla skleroza (MS) je hronično inflamatorno i neurodegenerativno oboljenje centralnog nervnog sistem (CNS) koju odlikuje izrazita heterogenost, počevši od patoloških procesa pa sve do kliničke slike i prognoze. Osim motornih ispada koji dovode do značajne invalidnosti ovih mladih ljudi, značajan broj bolesnika sa MS ima i kognitivne poremećaje koji se javljaju kod čak 40%-70% bolesnika, a koji mogu u velikoj meri da remete njihovo svakodnevno funkcionisanje i kvalitet života i bez prisutnog lokomotornog oštećenja. U poslednjih dvadesetak godina je interesovanje za ovu vrstu ispada u MS značajno poraslo i velika pažnja istraživača je usmerena na pokušaje objašnjenja mehanizama koji dovode do kognitivnih ispada u MS. To se pre svega odnosi na studije sa primenom magnentne rezonance (MR) koje pokušavaju da ustanove koji patološki procesi u mozgu bolesnika sa MS najviše doprinose nastanku i razvoju ovih, nemotornih, poremećaja. Dosadašnji rezultati neuroimidžing studija su pokazali kontradiktorne rezultate o mehanizmima nastanka kognitivnih oštećenja (KO) u MS, odnosno pokazali su da različiti patološki procesi koji se odvijaju u mozgu (multifoklani vs. difuzni, procesi u beloj masi vs. procesi u sivoj masi mozga) kod ovih bolesnika mogu da doprinesu nastanku KO, a najveći broj studija je uključivao heterogenu populaciju bolesnika sa MS. S obzirom da je pokazano da veliki broj parametara strukturalnog oštećenja mozga kod bolesnika od MS može da doprinose razvoju KO, retki su pokušaji da se, primenom sveobuhvaten analize procesa u mozgu i korišćenjem multiparametarskog modela identifikuju tzv. snažni MR „biomarkeri“ KO oštećenja u MS. Ciljevi studije su bili sledeći: 1. Analiza ukupne zapremine fokalnih lezija bele (na T2 i T1 sekvenci MR) i sive mase (kortikalni plakovi) kod bolesnika sa relapsno remitentnom MS (RRMS) sa KO i poređenje tih nalaza sa onim dobijenim kod bolesnika bez KO; 2. Analiza atrofije sive (SM) i bele mase (BM) mozga u navedene dve grupe bolesnika, kao i poređenje ovih parametara sa vrednostima dobijenim kod zdravih ispitanika; 3. Analiza atrofije subkortikalnih struktura sive mase (talamus, putamen, kaudatus, hipokampus, amigdaloidna jedra, nc. accumbens) kod bolesnika sa MS i utvrđivanje eventualnih razlika u volumenu ovih struktura između bolesnika sa i bez KO, kao i poređenje sa podacima dobijenim kod zdravih ispitanika; 4. Identifikacija seta MR varijabli nakon multiparametarske analize, koje najbolje koreliraju sa kognitivnim oštećenjima, primenom multivarijantne analize, a u cilju identifikacije da li inflamatorni (zapremina fokalnih lezija u beloj i sivoj masi mozga) ili pak, neurodegenerativni procesi (atrofija mozga, sive i bele mase, kao i atrofija subkortikalnih struktura, ukupna ili parcijalna) više doprinose nastanku kognitivnih ispada kod RRMS...Multiple sclerosis (MS) is chronic inflammatory and neurodegenerative disease of the central nervous system (CNS) characterized by various heterogenic pathological processes, clinical courses and prognosis. Beside motor deficits which lead to significant disability in these patients, cognitive impairment (CI) is a frequent finding in MS patients, with the prevalence ranges from 40% to70%. Although CI in MS has only been recognized recently as an important symptom over the past few decades, research has shown that they have a large effect on many everyday activities and quality of life. There has been an increased interest in research filed with a critical need to define pathological mechanisms of CI in MS. Magnetic resonance imaging (MRI) is extremely sensitive in detecting MS related tissue abnormalities, and broad spectrum of studies have been published so far in order to define which pathological mechanisms are the most responsible for CI in MS. However, results are still conflicting showing that both focal and diffuse brain damage, as well as both white matter (WM) and grey matter (GM) brain damage can contribute to CI development in MS. Most of these studies had heterogeneous population of MS patients. Despite these, multiparametric and comprehensive MR approach approach is still rare, especially in homogenous group of relapsing remitting MS (RRMS) patients. Aims of the study: 1. Assessment of total lesion volume of both WM (registered on T1W and T2W sequences) and GM (cortical lesions) in patients with RRMS with and without CI; 2. Analysis of both WM and GM brain atrophy in two groups of patients, as well as comparison with healthy controls (HC); 3. Analysis of volumetric measures of subcortical GM structures (thalamus, putamen, caudate, hippocampus, amygdala and accumbens) in both group of patients and their contribution to CI in MS, as well as comparison with the findings obtained in HC; 4. Identification of the set of MR imaging variables most closely associated with CI in RRMS using multivariant analysis in order to assess whether inflammatory pathology (lesion load in both WM and GM) or neurodegenerative processes (total brain atrophy, WM and GM atrophy and deep gray matter atrophy) are most responsible for CI in RRMS patients. Materials and methods: Subjects were recruited from January 2009 to May 2012 as part of a project on imaging correlates of CI in MS at 7 European centers, all part of MAGNIMS group ("Magnetic Resonance in Multiple Sclerosis") (www.magnims.eu). Patients included in the study had diagnosis of RRMS, using revised McDonald’s criteria. Also, study included HC with no neurological disease, which did not differ by gender..

Detection of malathion by the CO2-laser

Possibilities of detecting the vapour of the pesticide malathion by a CO2-laser, using a photoacoustic technique developed in our laboratory were investigated. A set of vapor photoacoustic spectra of coincidence with this laser were obtained, the samples being: the commercial product available on the market, solvent, emulsifiers, and neat malathion. Relative contributions of the components in the product are discussed.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Spectroscopic Study of An Icon Painted on Wooden Panel

Russian icon painted on wooden panel analyzed in this work is interesting for art historians because there is no precise information in which workshops it was made or who the author was. Similar icons are often found in churches and monasteries in our region. In order to obtain information about materials used for creation of investigated icon two micro-analytical techniques were used: Energy-Dispersive X-Ray Fluorescence spectroscopy (EDXRF) and micro-Raman spectroscopy. Obtained results confirmed presence of following materials: lead-white, vermilion, minium, ultramarine, brown and green earth pigments and silver in combination with yellow organic varnish, which served to an iconographer for gilding. Ground layer was made of calcite. Blue pigment ultramarine was probably used for blue colour as well as for obtaining particulars hues in several parts of the paint layer. This can be important information for further research concerning particular workshop in which the icon was made. Identified materials are typical for Russian iconography of the 19th century

Excitons in a Photosynthetic Light-Harvesting System: A Combined Molecular Dynamics/Quantum Chemistry and Polaron Model Study

The dynamics of pigment-pigment and pigment-protein interactions in light-harvesting complexes is studied with a novel approach which combines molecular dynamics (MD) simulations with quantum chemistry (QC) calculations. The MD simulations of an LH-II complex, solvated and embedded in a lipid bilayer at physiological conditions (with total system size of 87,055 atoms) revealed a pathway of a water molecule into the B800 binding site, as well as increased dimerization within the B850 BChl ring, as compared to the dimerization found for the crystal structure. The fluctuations of pigment (B850 BChl) excitation energies, as a function of time, were determined via ab initio QC calculations based on the geometries that emerged from the MD simulations. From the results of these calculations we constructed a time-dependent Hamiltonian of the B850 exciton system from which we determined the linear absorption spectrum. Finally, a polaron model is introduced to describe quantum mechanically both the excitonic and vibrational (phonon) degrees of freedom. The exciton-phonon coupling that enters into the polaron model, and the corresponding phonon spectral function are derived from the MD/QC simulations. It is demonstrated that, in the framework of the polaron model, the absorption spectrum of the B850 excitons can be calculated from the autocorrelation function of the excitation energies of individual BChls, which is readily available from the combined MD/QC simulations. The obtained result is in good agreement with the experimentally measured absorption spectrum.Comment: REVTeX3.1, 23 pages, 13 (EPS) figures included. A high quality PDF file of the paper is available at http://www.ks.uiuc.edu/Publications/Papers/PDF/DAMJ2001/DAMJ2001.pd

Spectroscopic investigation of milo milunović’s canvas painting “the inspiration of the poet”

A canvas painting by Milo Milunović “The Inspiration of the poet” was investigated in this work by multianalitical approach in order to identify pigments used by the artist as well as his painting technique. Results obtained by optical microscopy, fluorescence photography under UV light, energy dispersive X-Ray fluorescence (EDXRF) and FTIR Spectroscopy revealed following pigments on the painting: lead white, zinc white, cobalt blue, red pigment vermilion, green pigment viridian, as well as several earth colours. Optical micrographs show regions with no separation between layers, indicating that these areas were painted wet paint over wet paint

Physicochemical characterisation of pottery from the Vinca culture, Serbia, regarding the firing temperature and decoration techniques

A study of decorated Neolithic pottery samples from the excavation site Plocnik, Serbia, was performed using X-ray powder diffraction (XRPD), Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) spectroscopy. The investigated samples belong to the era of the Vinca culture that existed in the central Balkan region from the mid VI until the first half of the V millennium BCE. The mineralogical composition of the pottery samples and comparison of the investigated pottery with thermally treated local clay indicated firing temperatures in the range from 600 to 800 degrees C. Two different types of white pigments were identified in white incrusted decorations: calcium carbonate and bone white (composed of crushed bones). This is the first evidence of the use of bones for decorations in pottery of the Vinca culture from the excavation site Plocnik. In addition to this, it was revealed that the potters used the iron reduction technique for obtaining black decorations

Lambda production in 40 A GeV/c Pb-Au collisions

During the 1999 lead run, CERES has measured hadron and electron-pair production at 40 A GeV/c beam momentum with the spectrometer upgraded by the addition of a radial TPC. Here the analysis of lambda and antilambda will be presented.Comment: 8 pages, 8 figures. 6th International Conference on Strange Quarks in Matter, Frankfurt 200

Spectroscopic investigation of two Serbian icons painted on canvas

A multianalytical study of two Serbian icons, The Virgin and Child and St. Petka, painted on canvas by unknown authors was performed in order to identify the materials used as pigments, binders and the ground layer. The investigated icons belong to the Museum of the Serbian Orthodox Church in Belgrade. Samples, collected from different parts of the icons, were analysed by: optical microscopy (OM), energy dispersive X-Ray fluorescence (EDXRF), Fourier transform infrared (FTIR) and micro-Raman spectroscopy. The obtained results revealed the presence of the following pigments: Prussian Blue, ultramarine, Green Earth, iron oxides, Lead White and Zinc White. Linseed oil was used as the binder. The materials used for the ground layers were gypsum, calcite, baryte and Lead White. The gilded surface of the icon The Virgin and Child was made of gold. The gilded surface on the frame of this icon was made of imitation of gold, i.e., Schlagmetal, since EDXRF spectroscopy showed the presence of copper and zinc, while gold was not detected. Based on the style and the consideration of an art historian, as well as on the obtained results for the corresponding pigments and binder, both icons were most probably made at the end of 19th or the beginning of the 20th century