Comparative studies of the sensitivities of sparse and full geometries of Total-Body PET scanners built from crystals and plastic scintillators.

BACKGROUND: Alongside the benefits of Total-Body imaging modalities, such as higher sensitivity, single-bed position, low dose imaging, etc., their final construction cost prevents worldwide utilization. The main aim of this study is to present a simulation-based comparison of the sensitivities of existing and currently developed tomographs to introduce a cost-efficient solution for constructing a Total-Body PET scanner based on plastic scintillators. METHODS: For the case of this study, eight tomographs based on the uEXPLORER configuration with different scintillator materials (BGO, LYSO), axial field-of-view (97.4 cm and 194.8 cm), and detector configurations (full and sparse) were simulated. In addition, 8 J-PET scanners with different configurations, such as various axial field-of-view (200 cm and 250 cm), different cross sections of plastic scintillator, and multiple numbers of plastic scintillator layers (2, 3, and 4), based on J-PET technology have been simulated by GATE software. Furthermore, Siemens' Biograph Vision has been simulated to compare the results with standard PET scans. Two types of simulations have been performed. The first one with a centrally located source with a diameter of 1 mm and a length of 250 cm, and the second one with the same source inside a water-filled cylindrical phantom with a diameter of 20 cm and a length of 183 cm. RESULTS: With regards to sensitivity, among all the proposed scanners, the ones constructed with BGO crystals give the best performance ([Formula: see text] 350 cps/kBq at the center). The utilization of sparse geometry or LYSO crystals significantly lowers the achievable sensitivity of such systems. The J-PET design gives a similar sensitivity to the sparse LYSO crystal-based detectors while having full detector coverage over the body. Moreover, it provides uniform sensitivity over the body with additional gain on its sides and provides the possibility for high-quality brain imaging. CONCLUSION: Taking into account not only the sensitivity but also the price of Total-Body PET tomographs, which till now was one of the main obstacles in their widespread clinical availability, the J-PET tomography system based on plastic scintillators could be a cost-efficient alternative for Total-Body PET scanners.

Efficiency determination of J-PET: first plastic scintillators-based PET scanner.

BACKGROUND: The Jagiellonian Positron Emission Tomograph is the 3-layer prototype of the first scanner based on plastic scintillators, consisting of 192 half-metre-long strips with readouts at both ends. Compared to crystal-based detectors, plastic scintillators are several times cheaper and could be considered as a more economical alternative to crystal scintillators in future PETs. JPET is also a first multi-photon PET prototype. For the development of multi-photon detection, with photon characterized by the continuous energy spectrum, it is important to estimate the efficiency of J-PET as a function of energy deposition. The aim of this work is to determine the registration efficiency of the J-PET tomograph as a function of energy deposition by incident photons and the intrinsic efficiency of the J-PET scanner in detecting photons of different incident energies. In this study, 3-hit events are investigated, where 2-hits are caused by 511 keV photons emitted in [Formula: see text] annihilations, while the third hit is caused by one of the scattered photons. The scattered photon is used to accurately measure the scattering angle and thus the energy deposition. Two hits by a primary and a scattered photon are sufficient to calculate the scattering angle of a photon, while the third hit ensures the precise labeling of the 511 keV photons. RESULTS: By comparing experimental and simulated energy distribution spectra, the registration efficiency of the J-PET scanner was determined in the energy deposition range of 70-270 keV, where it varies between 20 and 100[Formula: see text]. In addition, the intrinsic efficiency of the J-PET was also determined as a function of the energy of the incident photons. CONCLUSION: A method for determining registration efficiency as a function of energy deposition and intrinsic efficiency as a function of incident photon energy of the J-PET scanner was demonstrated. This study is crucial for evaluating the performance of the scanner based on plastic scintillators and its applications as a standard and multi-photon PET systems. The method may be also used in the calibration of Compton-cameras developed for the ion-beam therapy monitoring and simultaneous multi-radionuclide imaging in nuclear medicine.

Size-dependent theoretical and experimental photothermal conversion efficiency of spherical gold nanoparticles.

INTRODUCTION: Due to their biocompatible and plasmonic properties, gold nanoparticles (Au NPs) are good candidates to be photosensitizers in photothermal cancer therapy (PTT). MATERIALS AND METHODS: In this paper, the dependence of the NIR-light-to-heat energy on Au NPs size was investigated. Moreover, to determine the photosensitizing properties of gold nanoparticles, PTT was conducted on two colon cell lines: SW480 and SW620 by irradiating them with two lasers having different wavelengths. RESULTS: Transmission electron microscopy showed that the respective sizes of Au NPs were 10 nm, 12 nm and 16 nm. Moreover, local as well as global structural measurements showed that all synthesized Au NPs were crystalline and UV-Vis spectroscopy revealed that with increasing nanoparticles size the position of the surface Plasmon resonance (SPR) peaks is shifted to higher wavelengths. Decrease of cells viability was observed, when they were cultured with Au NPs and irradiated by 650 nm and 808 nm lasers. Moreover, FTIR and Raman spectra of cells, showed structural changes in DNA, phospholipids, proteins and cholesterol caused by the addition of nanoparticles and laser irradiation. The chemical changes were more pronounced in the cells cultured with Au NPs and irradiated by 650 nm lasers and these changes were dependent on the nanoparticle size. Moreover, the viability of cells investigated by the MTS assay showed, that the percentage of dead cells (∼40%) is the highest for cells cultured with 8 nm Au NPs and irradiated by the 650 nm laser. The photothermal conversion efficiency calculated from the experimental results showed a decrease of this parameter from 70% to 55% and from 61% to 48% with increasing particle size, for 650 nm and 808 nm lasers, respectively. CONCLUSIONS: The obtained results showed that the photothermal conversion efficiency of Au NPs is size-tunable, and can be correlated with the absorption/extinction ratios calculated by the Mie theory.

Simulating NEMA characteristics of the modular total-body J-PET scanner-an economic total-body PET from plastic scintillators.

The purpose of the presented research is estimation of the performance characteristics of the economic total-body Jagiellonian-PET system (TB-J-PET) constructed from plastic scintillators. The characteristics are estimated according to the NEMA NU-2-2018 standards utilizing the GATE package. The simulated detector consists of 24 modules, each built out of 32 plastic scintillator strips (each with cross section of 6 mm times 30 mm and length of 140 or 200 cm) arranged in two layers in regular 24-sided polygon circumscribing a circle with the diameter of 78.6 cm. For the TB-J-PET with an axial field-of-view (AFOV) of 200 cm, a spatial resolutions (SRs) of 3.7 mm (transversal) and 4.9 mm (axial) are achieved. The noise equivalent count rate (NECR) peak of 630 kcps is expected at 30 kBq cc-1. Activity concentration and the sensitivity at the center amounts to 38 cps kBq-1. The scatter fraction (SF) is estimated to 36.2 %. The values of SF and SR are comparable to those obtained for the state-of-the-art clinical PET scanners and the first total-body tomographs: uExplorer and PennPET. With respect to the standard PET systems with AFOV in the range from 16 to 26 cm, the TB-J-PET is characterized by an increase in NECR approximately by factor of 4 and by the increase of the whole-body sensitivity by factor of 12.6 to 38. The time-of-flight resolution for the TB-J-PET is expected to be at the level of CRT = 240 ps full width at half maximum. For the TB-J-PET with an AFOV of 140 cm, an image quality of the reconstructed images of a NEMA IEC phantom was presented with a contrast recovery coefficient and a background variability parameters. The increase of the whole-body sensitivity and NECR estimated for the TB-J-PET with respect to current commercial PET systems makes the TB-J-PET a promising cost-effective solution for the broad clinical applications of total-body PET scanners. TB-J-PET may constitute an economic alternative for the crystal TB-PET scanners, since plastic scintillators are much cheaper than BGO or LYSO crystals and axial arrangement of the strips significantly reduces the costs of readout electronics and SiPMs.

[Study of practices: What do general practitioners first propose when faced with asymptomatic lower extremity peripheral artery disease?] / Enquête de pratiques : que proposent en premier les médecins généralistes devant une artériopathie asymptomatique des membres inférieurs ?

INTRODUCTION: Peripheral artery disease of lower limbs (PAD) can be discovered at an asymptomatic stage by the realization of systolic pressure indices. The 2006 recommendations of the French National Authority for Health on AOMI encourage the systematic prescription of antiplatelet agents; the 2012 recommendations on the proper use of antiplatelet agents no longer encourage it in the case of asymptomatic PAD. These two recommendations still coexist. Our objective was to determine the management of an asymptomatic PAD by general practitioners. METHODS: Descriptive and analytical epidemiological study, with analysis of practices, prospectively addressed by postal questionnaire to a randomized sample of 220 GPs practicing in the European Metropolis of Lille between December 15, 2016 and February 15, 2017. The question was: "if an asymptomatic PAD is discovered in a 50-year-old patient who is otherwise in good general condition, what do you generally do?" RESULTS: Our sample was 92 general practitioners (42% participation). Of these, only 6 were practicing HPIs. Before an asymptomatic PAD, management included an opinion from an angiologist (84%) and/or a cardiologist (75%) before the drug was prescribed (antiplatelet agent for 57%, statin for 33% and ACE inhibitor for 14%). CONCLUSION: The extension assessment was carried out in more than 8 out of 10 cases. The use of antiplatelet antiaggregants was significant, which can be explained by the coexistence of divergent recommendations. The rapid clarification of recommendations is essential with the evolution of scientific data.

From spherical to bone-shaped gold nanoparticles-Time factor in the formation of Au NPs, their optical and photothermal properties.

Using the same synthesis method, which was stopped at different time intervals, gold nanoparticles (Au NPs) with different shapes, from spherical to bone-shaped, were obtained. The physical properties of the synthesized Au NPs were investigated using transmission electron microscopy (TEM) combined with selected area electron diffraction patterns (SAED) and ultraviolet-visible spectroscopy (UV-vis). The TEM images showed, that stopping the synthesis after one minute lead to the formation of small spherical Au NPs, which evolved to the cubic shape, rods and bone-shaped Au NPs after 15 min, 30 min, 2 h, respectively. SAED patterns showed, that all the obtained Au NPs were crystalline. UV-vis spectra revealed, that the light absorbance depends on the shape of the Au NPs. Moreover, the effects of the time factor in the formation of Au NPs on the effective conversion of electromagnetic energy into thermal energy, was studied. Furthermore, simulated photothermal therapy (PTT) in combination with the obtained NPs, was done for two cancer cell lines SW480 and SW620. The mortality of cells after using the differently shaped Au NPs as photosensitizers is between 18 % and 52 % and increases with the decrease of the synthesis time.

Size effect of platinum nanoparticles in simulated anticancer photothermal therapy.

Platinum nanoparticles (Pt NPs) with properties including damage of DNA, enzmatic activity and possibility of light absorption in the biological range could find application as effective photosensitizers in photothermal anticancer therapy (PTT). The photothermal properties of Pt NPs depend on their shape, size and crystalline structure. Therefore, in this paper the effect of Pt NPs size on photothermal efficiency is determined. For this purpose, spherical, crystalline 80 nm PtI NPs and 2 nm PtII NPs were synthesized and characterized by transmission electron microscopy (TEM), selected area diffraction patterns (SAED) and X-ray diffraction (XRD). The possibilities of using Pt NPs in PTT were investigated using two colon cancer cell lines: SW480 and SW620, which were cultured with both Pt NPs and irradiated by two, 650 nm and 808 nm lasers. Microscopy images of cells and MTS assay showed, that the PTT is the most effective when 2 nm nanoparticles and the 650 nm laser were used. The mortality of cells was around 62% for SW480 and 70% for SW620. Furthermore, higher temperatures after irradiation of Pt NPs by lasers were observed for the 2 nm Pt NPs for both wavelengths. Consequently, the values of photothermal efficiency are higher by approximately 5% and 6% for 2 nm Pt NPs, than for 80 nm ones, which were irradiated by 650 and 808 nm lasers, respectively. Moreover, the results obtained from experimental data corresponded with Mie theory.

Platinum-gold nanoraspberries as effective photosensitizer in anticancer photothermal therapy.

BACKGROUND: New nanophotosensitizers for photothermal cancer therapy (PTT) are still sought. In this paper we propose fancy shaped, non agglomerated core/shell PtAu NRs nanoraspberries (PtAu NRs) as potential nanophotosensitizers in PTT. RESULTS: Light microscopy images of two colon cancer cell lines (SW480, SW620) showed, that the laser irradiation combined with PtAu NRs caused visible changes in the cell morphology. Fourier Transform InfraRed (FTIR) and Raman spectroscopies showed chemical changes in the DNA, phospholipids, lipids and protein structures caused by laser irradiation in the presence of PtAu NRs. The MTS assay showed ~ 25% mortality of cancer cells due to the addition of PtAu NRs to the cell culture, while for laser irradiation combined with nanoparticles, the mortality of cancer cells increased to 65% for the 650 nm laser and to 60% for the 808 nm laser. The calculated photothermal conversion efficiency reached 62% and 51% for the 650 nm and 808 nm lasers, respectively. CONCLUSIONS: PtAu NRs could be applied as effective light-absorbers in the PTT anticancer therapy.

The role of chemokine CCL5/RANTES and metalloproteinase-9 as inflammatory modulators in symptomatic internal carotid artery stenosis.

Up to 80% of all ischemic strokes (IS) attributed to internal carotid athero-occlusive artery stenosis (ICAS) are related to a thromboembolic mechanism. One athero-occlusive ischemic event increases the risk for ischemia in another vascular territory, resulting from inflammation within the atherosclerotic plaque induced by cytokines. Thus, ultrasonographic characteristics of vulnerable plaques in ICAS, including plaque echolucency and ulceration might correspond to cytokine activity. The present study aimed to investigate the associations between serum cytokines and atherosclerotic plaque characteristics and the 3-year risk of a major adverse coronary and carotid ischemic event (MACCE) in symptomatic patients treated for ICAS. Plaque characteristics on ultrasonography, serum levels of C-C motif chemokine ligand 5 (CCL5)/regulated on activation, normal T-cell expressed and secreted (RANTES), metalloproteinase-9 (MMP-9), interleukin-6 (IL-6), transforming growth factor beta (TGF-ß), C-X-C motif chemokine ligand 16 (CXCL16), FAS ligand (FASL) and high sensivity C-reactive protein (hs-CRP) were analyzed in 103 symptomatic patients with ICAS prior to carotid revascularization. The incidence of MACCE: cardiovascular death (CVD), myocardial infarction (MI) and recurrent ischemic stroke (IS) were recorded prospectively for up to 5 years (median 37; IQR 21 - 40 months). Echolucent plaques, in comparison to echogenic plaques, displayed lower median levels of RANTES (P = 0.042) but higher median levels of IL-6 (P = 0.039). There was no relationship between plaque characteristics and median levels of MMP-9, TGF ß, CXCL16, FASL, or hs-CRP (P = NS). During follow-up, MACCE occurred in 15 (14.6%) patients. Univariate Cox proportional hazard analysis indicated median RANTES levels < 45.5ng/mL (hazard ratio (HR) = 3.95; 95%CI = 1.10 - 14.2; P = 0.035), MMP-9 > 0.6 µg/mL (HR 4.5; 95%CI = 1.4 - 13.9; P = 0.009), renal impairment (HR 3.48; 95%CI = 1.29 - 9.34; P = 0.013) as potential MACCE risk factors. On multivariate Cox proportional hazard analysis, MMP-9 > 0.6 µg/mL and RANTES < 45.5 ng/ml were associated with a 4.72-fold (95%CI = 1.3 - 17.0; P = 0.017) and a 3.8-fold risk increase (95%CI = 1.07 - 13.89; P = 0.038) of MACCE. Kaplan-Meier analysis showed significant differences in MACCE-free survival rates depending on RANTES and MMP-9 median levels. We conclude that serum RANTES, IL-6, and MMP-9 were associated with plaque vulnerability and predicted adverse MACCE in patients treated for ICAS.

Serum rantes, transforming growth factor-ß1 and interleukin-6 levels correlate with cardiac muscle fibrosis in patients with aortic valve stenosis.

Regulated on Activation Normal T Expressed and Secreted (RANTES) chemokine is involved in the initiation of inflammation and immune-cell recruitment. Interleukin -6 (IL-6) is used as a general index of severity of the chronic inflammatory process. Finally, transforming growth factor-ß (TGF-ß) is an immune biomarker potentially involved in the regulation of valve fibrosis and calcification. The aim of this study was to analyze selected biomarkers associated with the different stages of immune-pathogenesis in aortic stenosis. Forty consecutive patients with moderate to severe aortic stenosis (AS) and without previous myocardial infarction history were included in the study and divided into two groups. Two imaging techniques, echocardiography and magnetic resonance, were used to estimate the degree of AS and left ventricular muscle function. Inflammatory biomarker serum levels including CCL5/RANTES, IL-6, and TGF-ß1 were determined based on ELISA measurements. Mean levels of RANTES, IL-6, and TGF-ß1 did not significantly differ between both groups. A negative correlation was found between RANTES serum level and left ventricle (LV) mass as assessed by MRI (r = -0.3358, P = 0.0341). A positive correlation (r = 0.3283, P = 0.0387) was found between IL-6 serum levels and LV mass as measured by MRI. In addition, a positive correlation (r = 0.6803, P = 0.01) was seen between IL-6 serum levels and LV muscle mass with positive late gadolinium enhancement (LGE). There was a positive correlation between TGF-ß1 serum level and ejection fraction as measured by echocardiography (r = 0.3217, P = 0.043). The relationship between selected inflammatory biomarkers, LV ejection fraction, LV mass, and LV muscle mass with LGE appeared to be independent of valvular pathobiologic process severity, as we did not observe differences in IL-6, RANTES, or TGF-ß1 between groups differing in severity. On the contrary, these markers appear to be linked to myocardial function and remodeling, which may provide valuable insights into the pathobiology of AS and provide a basis for future detection strategies of AS.

Widely used hardly known. An insight into electric and dynamic properties of formamidinium iodide.

The simple organic crystal formamidinium iodide (FAI) appeared to be a novel semiconducting material in a wide temperature range. The electric properties of FAI and the role of formamidinium cation (FA+) in the molecular mechanism of the solid-to-solid phase transitions (at 345 K (III → II) and 388 K (II → I)) were analysed. The creation of the ferroelastic domain structure in phases III and II was proved on the basis of observation under a polarizing microscope. Moreover, the molecular arrangement of dipolar organic FA+ was studied by 1H NMR (spin-lattice relaxation time) and vibrational spectroscopy supported by density functional theory. The theoretical results show a good agreement with the experimental data. The infrared spectrum in a harmonic approximation was calculated and a comparative vibrational analysis was performed. All used techniques showed that the prototypic phase I exhibits the feature of plastic phase.

Fourier transform infrared and Raman spectroscopy in the study of phase transitions in dipyrazolium iodide triiodide: Experimental and theoretical analysis.

The paper presents the Infrared and Raman spectra of the powdered [C3N2H5+]2[I-∙I3-] crystal at the temperature intervals of 11-270K, covering two low-temperature phase transitions: discontinuous at 182/188K (cooling/heating) and continuous at 254K. The research shows that the vibrational states of the pyrazolium cations change significantly during discontinuous phase transition (III→II), while the continuous nature of successive structural transformation is more subtle and displays an insignificant change in the temperature coefficient of numerous vibrations during the II→I PT at 254K. The spectacular changes at Raman spectra above 188K confirm a huge rebuilding of inorganic network from [I-∙I3-] to [I42-]. Additionally, a complete geometry optimization was carried out in the solid state in order to obtain minimum structures and bonding properties. The theoretical results correspond well with the experimental data. Moreover, the infrared spectrum in harmonic approximation was calculated, and a comparative vibrational analysis was performed. CRYSTAL09 vibrational results appear to be in a good agreement with the experimental ones.

Spectroscopy of the Surface Polaritons in the CdXZn(1-X)P2 Solid Solutions.

Here we report on the analysis of the effect of the doping of CdP2 single crystals by ZnP2 nanoclusters on the dispersion of the surface polaritons (SP). The ATR spectroscopic technique has been applied to excite the SP in the CdXZn(1-X)P2 system. Analysis of the obtained spectra has shown that the doping of CdP2 single crystals by ZnP2 nanoclusters result in the position and the width of the dispersion branches of the SP. This effect is more pronounced in the low frequency dispersion branches. These SP branches are originated from phonons which correspond to the motion of the cation sublattice.

The Role of ZnP2 Nanoclusters in the Vibrational Properties of Cd x Zn(1 - x)P2 Solid Solutions.

This study reports an analysis of the IR reflectance and Raman spectra of Cd x Zn(1 - x)P2 solid solutions. We have analyzed the effect of the doping of the CdP2 single crystal by the ZnP2 nanoclusters on the vibrational properties of studied samples: ε 0, ε inf, phonon frequencies, and strengths. These dependencies might be used as an alternative non-destructive way for the control of the Cd x Zn(1 - x)P2 composition. The obtained results show that variation of the concentration of ZnP2 nanoclusters opens a space to design the tailored material properties for the industrial applications.

Measuring the mechanical properties of molecular conformers.

Scanning probe-actuated single molecule manipulation has proven to be an exceptionally powerful tool for the systematic atomic-scale interrogation of molecular adsorbates. To date, however, the extent to which molecular conformation affects the force required to push or pull a single molecule has not been explored. Here we probe the mechanochemical response of two tetra(4-bromophenyl)porphyrin conformers using non-contact atomic force microscopy where we find a large difference between the lateral forces required for manipulation. Remarkably, despite sharing very similar adsorption characteristics, variations in the potential energy surface are capable of prohibiting probe-induced positioning of one conformer, while simultaneously permitting manipulation of the alternative conformational form. Our results are interpreted in the context of dispersion-corrected density functional theory calculations which reveal significant differences in the diffusion barriers for each conformer. These results demonstrate that conformational variation significantly modifies the mechanical response of even simple porpyhrins, potentially affecting many other flexible molecules.

Crystal structure and thermoelectric properties of Sr-Mo substituted CaMnO3: a combined experimental and computational study.

A combination of experimental and computational techniques has been employed to study doping effects in perovskite CaMnO3. High quality Sr-Mo co-substituted CaMnO3 ceramics were prepared by the conventional mixed oxide route. Crystallographic data from X-ray and electron diffraction showed an orthorhombic to tetragonal symmetry change on increasing the Sr content, suggesting that Sr widens the transition temperature in CaMnO3 preventing phase transformation-cracking on cooling after sintering, enabling the fabrication of high density ceramics. Atomically resolved imaging and analysis showed a random distribution of Sr in the A-site of the perovskite structure and revealed a boundary structure of 90° rotational twin boundaries across {101}orthorhombic; the latter are predominant phonon scattering sources to lower the thermal conductivity as suggested by molecular dynamics calculations. The effect of doping on the thermoelectric properties was evaluated. Increasing Sr substitution reduces the Seebeck coefficient but the power factor remains high due to improved densification by Sr substitution. Mo doping generates additional charge carriers due to the presence of Mn3+ in the Mn4+ matrix, reducing electrical resistivity. The major impact of Sr on thermoelectric behaviour is the reduction of the thermal conductivity as shown experimentally and by modelling. Strontium containing ceramics showed thermoelectric figure of merit (ZT) values higher than 0.1 at temperatures above 850 K. Ca0.7Sr0.3Mn0.96Mo0.04O3 ceramics exhibit enhanced properties with S1000K = -180 µV K-1, ρ1000K = 5 × 10-5 Ωm, k1000K = 1.8 W m-1 K-1 and ZT ≈ 0.11 at 1000 K.

Polymorphism of triphenyl phosphite.

The glass-forming liquid triphenyl phosphite (TPP) has recently attracted much attention due to the possible existence of a polyamorphism, i.e., the existence of two or more amorphous phases. In the present work we provide experimental evidence of the existence of a polymorphism in TPP. In addition to the already known conventional crystalline phase, which melts at 299.1 K, it has been found that TPP can crystallize in another polymorphic phase. The new polymorph can be obtained from the liquid phase due to direct cooling from the room temperature up to 245 K where it is held for 15 min and then heated up to 270 K. At 270 K crystallization of the new polymorph occurs, which melts at 291.6 K.

4,4'-, 5,5'-, and 6,6'-dimethyl-2,2'-bipyridyls: the structures, phase transitions, vibrations, and methyl group tunneling of their complexes with chloranilic acid.

The crystal and molecular structures of 4,4(')- and 6,6(')-dimethyl-2,2(')-bipyridyl complexes with 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (chloranilic acid, CLA) have been determined and compared with those of the complex with the 5,5(')-derivative, which is known to possess interesting antiferroelectric properties. In the crystalline state, all three compounds form hydrogen bonded chains with N(+)-H···O(-) and O-H···N bridges on both sides of the bipyridyl constituent. The comparison of three derivatives indicates that the N(+)-H···O(-) hydrogen bonds are shortest for the 5,5(')-dimethyl complex. The 4,4(')- and 6,6(')-derivatives do not show any ferroelectric feature. The 6,6(')-one is, however, characterized by a continuous phase transition, revealed in the differential scanning calorimetry, dilatometric, and dielectric characteristics. The tunneling splitting measured by neutron backscattering in the energy range ±30 µeV for the neat dimethyl bipyridyls and their complexes with CLA indicates that the different splittings are primarily due to the crystal packing effect and that charge transfer between interacting compounds plays only a minor role.

Antileukemic action of (-)-epicatechin in the spleen of rats with acute myeloid leukemia.

The aim of this study was to investigate whether (-)-epicatechin (EC) can induce DNA damage and apoptosis of cancer cells in the spleen of rat with acute myeloid leukemia. Healthy and leukemic rats were given EC by gavage at a dose of 40 mg/kg b.w. for 22 consecutive days. Spleen cells were subjected for analysis of DNA damage and apoptosis. The amount of DNA damage was estimated by the comet assay, while apoptosis was examined by flow cytometry using Annexin V staining. Leukemic cells were identified in the spleen cells by indirect immunofluorescence using RM-124 antibody followed by flow cytometry analysis. The results show that EC did not affect DNA damage in the splenocytes of healthy rats, but significantly increased the extent of DNA strand breaks in the spleen cells of leukemic animals. EC administration to leukemic rats induced a significant increase in the level of Annexin V-positive leukemic cells, but the level of non-leukemic Annexin V-positive cells remained unchanged in comparison to control. The percentage of leukemic cells decreased significantly under EC influence comparing to the untreated group. The results of the study reveal that EC could be used as an effective supplement of standard therapy against acute myeloid leukemia.

Infrared spectroscopy study of structural changes in glass-forming salol.

We report the investigation of glass-forming salol upon different courses of the temperature changes from liquid to glass state and back using FT-IR spectroscopy measurements in the wide spectral and temperature ranges. The formation of the ordered clusters in supercooled liquid salol has been observed at 250 K. When the temperature is decreased further to 11 K these ordered clusters become an element of the glass structure. With increasing temperature to 270 K through the glass transition noticeable evolutions of the IR spectrum occurs up till the ordered clusters are developed into crystal. So produced crystal melts in the temperature range 300-310 K, that corresponds to the melting temperature of the metastable phase (Tmelt=302 K) . Thus, the crystalline structure of the ordered clusters corresponds to the structure of metastable phase and is monoclinic.