Multifaceted Quadruplet of Low-Lying Spin-Zero States in

A search for shape isomers in the ^{66}Ni nucleus was performed, following old suggestions of various mean-field models and recent ones, based on state-of-the-art Monte Carlo shell model (MCSM), all considering ^{66}Ni as the lightest nuclear system with shape isomerism. By employing the two-neutron transfer reaction induced by an ^{18}O beam on a ^{64}Ni target, at the sub-Coulomb barrier energy of 39 MeV, all three lowest-excited 0^{+} states in ^{66}Ni were populated and their γ decay was observed by γ-coincidence technique. The 0^{+} states lifetimes were assessed with the plunger method, yielding for the 0_{2}^{+}, 0_{3}^{+}, and 0_{4}^{+} decay to the 2_{1}^{+} state the B(E2) values of 4.3, 0.1, and 0.2 Weisskopf units (W.u.), respectively. MCSM calculations correctly predict the existence of all three excited 0^{+} states, pointing to the oblate, spherical, and prolate nature of the consecutive excitations. In addition, they account for the hindrance of the E2 decay from the prolate 0_{4}^{+} to the spherical 2_{1}^{+} state, although overestimating its value. This result makes ^{66}Ni a unique nuclear system, apart from ^{236,238}U, in which a retarded γ transition from a 0^{+} deformed state to a spherical configuration is observed, resembling a shape-isomerlike behavior.

Substrate surface patterning by optical near field modulation around colloidal particles immersed in a liquid.

Optical near field enhancements in the vicinity of particles illuminated by laser light are increasingly recognized as a powerful tool for nanopatterning applications, but achieving sub-wavelength details from the near-field distribution remains a challenge. Here we present a quantitative analysis of the spatial modulation of the near optical fields generated using single 8 ps, 355 nm (and 532 nm) laser pulses around individual colloidal particles and small close packed arrays of such particles on silicon substrates. The analysis is presented for particles in air and, for the first time, when immersed in a range of liquid media. Immersion in a liquid allows detailed exploration of the effects on the near field of changing not just the magnitude but also the sign of the refractive index difference between the particle and the host medium. The level of agreement between the results of ray tracing and Mie scattering simulations, and the experimentally observed patterns on solid surfaces, should encourage further modelling, predictions and demonstrations of the rich palette of sub-wavelength surface profiles that can be achieved using colloidal particles immersed in liquids.

Pattern formation on silicon by laser-initiated liquid-assisted colloidal lithography.

We report sub-diffraction limited patterning of Si substrate surfaces by laser-initiated liquid-assisted colloidal lithography. The technique involves exposing a two-dimensional lattice of transparent colloidal particles spin coated on the substrate of interest (here Si) immersed in a liquid (e.g. methanol, acetone, carbon tetrachloride, toluene) to a single picosecond pulse of ultraviolet laser radiation. Surface patterns formed using colloidal particles with different radii in the range 195 nm ≤ R ≤ 1.5 µm and liquids with differing indices of refraction (n(liquid)) are demonstrated, the detailed topographies of which are sensitively dependent upon whether the index of refraction of the colloidal particle (n(colloid)) is greater or smaller than n liquid (i.e. upon whether the incident light converges or diverges upon interaction with the particle). The spatial intensity modulation formed by diffraction of the single laser pulse by the colloidal particles is imprinted into the Si substrate.

Ultrafast hydrogen bond dynamics and partial electron transfer after photoexcitation of diethyl ester of 7-(diethylamino)-coumarin-3-phosphonic acid and its benzoxaphosphorin analog.

The solvation dynamics after optical excitation of two phosphono-substituted coumarin derivatives dissolved in various solutions are studied by fluorescence up-conversion spectroscopy and quantum chemical simulations. The Kamlet-Taft analysis of the conventional absorption and emission spectra suggests weakening of the solvent-solute H-bonds upon optical excitation, which is in contrast to the results gained by the quantum simulations and earlier studies reported for coumarin derivatives without phosphono groups. The simulations give evidence that the solvent reorganisation around the excited fluorophore leads to partial electron transfer to the first solvation shell. The process occurs on a timescale between 1 and 10 ps depending on the solvent polarity and leads to a fast decay of the time-resolved emission signal. Using the ultrafast spectral shift of the time-dependent fluorescence we estimated the relaxation time of the H-bonds in the electronically excited state to be about 0.6 ps in water, 1.5 ps in ethanol and 2.8 ps in formamide.

Candidates for twin chiral bands in 102Rh.

Excited states in 102Rh, populated in the fusion-evaporation reaction Zr94(11B,3n)102Rh at a beam energy of 36 MeV, were studied using the Indian National Gamma Array spectrometer at Inter University Accelerator Center, New Delhi. The angular correlations and the electromagnetic character of some of the gamma-ray transitions observed were investigated in detail. A new chiral candidate sister band was found. Lifetimes of exited states in both chiral candidate bands of 102Rh were measured for the first time in the A∼100 mass region by means of the Doppler-shift attenuation technique. The derived reduced transition probabilities are compared to the predictions of the two quasiparticles plus triaxial rotor model. Both experimental results and calculations do not support the presence of static chirality in 102Rh.

Evaluation of QSAR models for predicting mutagenicity: outcome of the Second Ames/QSAR international challenge project.

Quantitative structure-activity relationship (QSAR) models are powerful in silico tools for predicting the mutagenicity of unstable compounds, impurities and metabolites that are difficult to examine using the Ames test. Ideally, Ames/QSAR models for regulatory use should demonstrate high sensitivity, low false-negative rate and wide coverage of chemical space. To promote superior model development, the Division of Genetics and Mutagenesis, National Institute of Health Sciences, Japan (DGM/NIHS), conducted the Second Ames/QSAR International Challenge Project (2020-2022) as a successor to the First Project (2014-2017), with 21 teams from 11 countries participating. The DGM/NIHS provided a curated training dataset of approximately 12,000 chemicals and a trial dataset of approximately 1,600 chemicals, and each participating team predicted the Ames mutagenicity of each trial chemical using various Ames/QSAR models. The DGM/NIHS then provided the Ames test results for trial chemicals to assist in model improvement. Although overall model performance on the Second Project was not superior to that on the First, models from the eight teams participating in both projects achieved higher sensitivity than models from teams participating in only the Second Project. Thus, these evaluations have facilitated the development of QSAR models.

Simple new methods for deducing lifetimes in recoil distance Doppler-shift measurements.

New approaches for lifetime determination using data from recoil distance Doppler-shift experiments are presented based on the fundamental properties of the functions describing the time evolution of the population of excited nuclear states. To some extent, one of them represents a contraction of the well-known Differential decay-curve method (DDCM) by using the most reliable data point [the maximum of the ni(t) function describing the population of level i in time] and a purely numerical procedure avoiding any fitting of decay curves. The combination with the standard DDCM analysis is promising for improving the reliability and the precision of the results for the lifetimes obtained. The novel part of the approach consists of using a chain of equations at the consecutive maxima of the ni(t) functions, which allow us to precisely determine the ratio of the lifetimes of two consecutive levels and, in the case where one of these lifetimes is known, to determine the unknown one. In addition, a simple integral derivation of the lifetime is presented involving the peak areas measured at different distances, and an application of the first moments (expectation values and centroids in time) of the ni(t) functions for determining lifetimes is also demonstrated to be useful.

Enhanced quadrupole collectivity at N = 40: the case of neutron-rich Fe isotopes.

The transition rates for the 2(1)+ states in (62,64,66)Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N = 40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N = 40 as governed by the number of valence protons with respect to Z ≈ 30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space.

Novel manifestation of alpha-clustering structures: new "alpha+208Pb" states in 212Po revealed by their enhanced E1 decays.

Excited states in 212Po were populated by alpha transfer using the 208Pb(18O,14C) reaction, and their deexcitation gamma rays were studied with the Euroball array. Several levels were found to decay by a unique E1 transition (Egamma<1 MeV) populating the yrast state with the same spin value. Their lifetimes were measured by the Doppler-shift attenuation method. The values, found in the range 0.1-1.4 ps, lead to very enhanced transitions, B(E1)=2x10(-2)-1x10(-3) W.u. These results are discussed in terms of an alpha-cluster structure which gives rise to states with non-natural-parity values, provided that the composite system cannot rotate collectively, as expected in the "alpha+208Pb" case. Such states due to the oscillatory motion of the alpha-core distance are observed for the first time.

Ultrahigh-resolution γ-ray spectroscopy of 156Gd: a test of tetrahedral symmetry.

Tetrahedral symmetry in strongly interacting systems would establish a new class of quantum effects at subatomic scale. Excited states in 156Gd that could carry the information about the tetrahedral symmetry were populated in the 155Gd(n,γ)156Gd reaction and studied using the GAMS4/5 Bragg spectrometers at the Institut Laue-Langevin. We have identified the 5(1)- → 3(1)- transition of 131.983(12) keV in 156Gd and determined its intensity to be 1.9(3)x10(-6) per neutron capture. The lifetime τ=220(-30)(+180) fs of the 5(1)- state in 156Gd has been measured using the GRID technique. The resulting B(E2)=293(-134)(+6) Weisskopf unit rate of the 131.983 keV transition provides the intrinsic quadrupole moment of the 5(1)- state in 156Gd to be Q0=7.1(-1.6)(+0.7) b. This large value, comparable to the quadrupole moment of the ground state in 156Gd, gives strong evidence against tetrahedral symmetry in the lowest odd-spin, negative-parity band of 156Gd.

Induction of abortion with aglepristone in cats on day 45 and 46 after mating.

The aim of this study was to test for the efficacy and safety of the use of aglepristone for pregnancy termination on day 45 in cats. Six healthy cats were treated with 10 mg/kg aglepristone sc on day 45 and 46 after mating; six other cats served as untreated controls. The effect of treatment was monitored by general examination, vaginal cytology, ultrasonography and blood sampling for haematology and progesterone determination. Besides, interoestrus interval and next pregnancy including litter size were recorded. The efficacy of treatment was approximately 67% (4/6) with abortion occurring 4-7 days after the first injection and a sanguineous discharge and erythrocytes in vaginal smears for at least 6 days afterwards. The two treated cats that did not abort gave birth to two kittens on day 67 and had a stillbirth of a single kitten on day 71, respectively. As expected enlargement of the mammary glands and lactation were observed in all treated cats. No other treatment-induced side effects were observed. Progesterone levels at abortion were high (30-140 nmol/l), but were decreased on day 55. Aglepristone treatment did not affect fertility in following cycles. Finally, it can be concluded that late-term pregnancy termination with aglepristone is possible but due to a success rate of 67% an ultrasonographical examination 7 days after treatment is an inherent necessity to control the effect of treatment.

Computational study of solution behavior of magainin 2 monomers.

Antimicrobial peptides (AMPs) play crucial role as mediators of the primary host defense against microbial invasion. They are considered a promising alternative to antibiotics for multidrug resistant bacterial strains. For complete understanding of the antimicrobial defense mechanism, a detailed knowledge of the dynamics of peptide-membrane interactions, including atomistic studies on AMPs geometry and both peptide and membrane structural changes during the whole process is a prerequisite. We aim at clarifying the conformation dynamics of small linear AMPs in solution as a first step of in silico protocol for establishing a correspondence between certain amino-acid sequence motifs, secondary-structure elements, conformational dynamics in solution and the intensity and mode of interaction with the bacterial membrane. To this end, we use molecular dynamics simulations augmented by well-tempered metadynamics to study the free-energy landscape of two AMPs with close primary structure and different antibacterial activity - the native magainin 2 (MG2) and an analog (MG2m, with substitutions F5Y and F16W) in aqueous solution. We observe that upon solvation, the initial α-helical structures change differently. The native form remains structured, with three shorter α-helical motifs, connected by random coils, while the synthetic analog tends predominantly to a disordered conformation. Our results indicate the importance of the side-chains at positions 5 and 16 for maintaining the solvated peptide conformation. They also provide a modeling background for recent experimental observations, relating the higher α-helical content in solution (peptide pre-folding) in the case of small linear AMPs to a lower antibacterial activity.

Liver regeneration and alpha-fetoprotein messenger RNA expression in the retrorsine model for hepatocyte transplantation.

Recently, we described a new model for hepatocyte transplantation with nearly total replacement of the liver by exogenous hepatocytes (E. Laconi et al., Am. J. Pathol., 153: 319-329, 1998). The model is based on the mitoinhibitory effect of the pyrrolizidine alkaloid retrorsine on hepatocytes in the resident liver while transplanted hepatocytes proliferate. In this study, we exploit this novel approach to address the important and controversial issue of whether hepatocytes, when proliferating extensively, undergo dedifferentiation and give rise to foci of undifferentiated hepatocytes. Genetically marked hepatocytes (isolated from normal Dipeptidyl peptidase IV+ Fischer 344 rats) were delivered intraportally (2 x 10(6) cells) into the liver of retrorsine-treated Dipeptidyl peptidase IV- mutant Fischer 344 rats in conjunction with partial hepatectomy. Transplanted hepatocytes were detected histochemically or immunohistochemically, and cell proliferation was studied by in situ hybridization for histone-3 mRNA. Expression of alpha-fetoprotein (AFP) mRNA, a marker of hepatocyte dedifferentiation, was also revealed by in situ hybridization. One day after partial hepatectomy and hepatocyte transplantation, endogenous hepatocytes and oval cells expanding in the liver expressed histone-3 mRNA (cells had entered S phase); 2 days later, transplanted hepatocytes and nonparenchymal cells also expressed histone-3 mRNA. Although the majority of endogenous hepatocytes did not divide and became arrested as quiescent megalocytes, the exogenous hepatocytes, as well as newly formed small hepatocytes, most probably derived from liver progenitor cells, underwent extensive proliferation. After 7-14 days, the nonparenchymal cells stopped proliferating, but transplanted hepatocytes and small endogenous hepatocytes continued to proliferate for 1 month, forming foci of dividing parenchymal cells. Although many of the hepatocytes in clusters were in S phase (histone-3 mRNA positive), none expressed AFP mRNA. In contrast, high expression of AFP mRNA was observed in proliferating oval and transitional cells, forming duct-like structures of cytokeratin-19-positive cells. From these studies, we conclude that hepatocyte proliferation in the adult liver is not associated with dedifferentiation.

[Novelties in the Treatment of Colorectal Diseases - An Echo from the 10-th ESCP Congress].

Treatment of colorectal pathology stands continuous development. One of the promotional leaders of the new therapeutic approaches is the European Society of Coloproctology (ESCP). The annual congress of the organization held in Dublin, Ireland and it unites the elite of European Community countries. The most advanced scientific knowledge of the diseases of the colon and rectum, anal canal and perineum was presented.

Controlling embedment and surface chemistry of nanoclusters in metal-organic frameworks.

A combined theoretical and experimental approach demonstrates that nanocluster embedment into the pores of metal-organic frameworks (MOF) may be influenced by the chemical functionalisation of the MOF. Furthermore, this results in the surface functionalisation of the embedded nanoclusters, highlighting the potential of MOF scaffolds for the design and synthesis of novel functional materials.

Latent autoimmune diabetes mellitus in adult humans with non-insulin-dependent diabetes: is Psammomys obesus a suitable animal model?

Recent data suggest that in a proportion of NIDDM patients there is a slowly evolving insulitis which results in a latent autoimmune diabetes leading to full insulin-dependence. Many animal models exist of NIDDM but none have reported the spontaneous existence of a similar phenomenon. We have re-examined the histology of pancreata from a few Psammomys obesus who had become insulin-dependent in the late stages of NIDDM. We report here the unexpected finding of the presence of insulitis in these animals and suggest that they could be a model for the clinical observation of latent IDDM in NIDDM patients.

Histological and histochemical investigations on the Langerhans' islets of the frog (Rana ridibunda).

The Langerhans' islets of the frog Rana ridibunda are built up of A, B, and D cells like other vertebrates. The phospholipids (Baker's test) are located in the capillary pole of the B-Cells, where also beta-granules are present. In the cells of the endocrine pancreas there is found also some quantity of glycogen, but the reaction for zink is negative. The quantity of RNA in the cytoplasme of the islet's cells is minimum.

Laser microprobe of cryostate sections of pancreas.

Laser microprobe was utilized in order to differentiate chemically the elementary composition of the A and B cells of Langerhans' islets and the exocrine parenchyma of the pancreas. An additional magnetic field was applyed to increase the sensitivity of the method.

A morphological and immunohistochemical investigation of endocrine pancreata from obese ob+/ob+ mice.

There is a marked difference in insulin secretion between the ob+/ob+ obese mouse and its non-obese littermate. Numerous peptides have been implicated in the modification of postprandial insulin secretion. In this study, the morphological and immunohistochemical studies of the genetically obese mouse (ob+/ob+) pancreata were compared with control littermates. Additionally, the distribution of gastric inhibitory polypeptide, somatostatin, glucagon, and insulin immunoreactive cells was also quantitated. Hyperglycemia and hyperinsulinemia were verified in the obese mice. The control animals had some islets and ductules with mononuclear infiltrations of a possible immune character. The obese individuals had a marked increase in both number and size of the islets of Langerhans compared with lean controls. The insulin immunocytochemical reaction in the obese pancreatic beta-cells was weaker than that of controls, as was the aldehyde-fuchsin reaction. The glucagon, gastric inhibitory polypeptide, and somatostatin containing cells were intermingled with the beta-cells. In contrast, the control animals showed a peripheral localization of these cell types. The morphometric analysis of the obese pancreas showed a decreased proportion of non-beta cells within the islets but not in total pancreatic volume in comparison with controls. The obese mouse also had cavities filled with eosin-stained material among numerous beta-cells. No complete epithelial lining distinguished these formations from the surrounding islet cells. The content of the cavities was not stained by any of the immunocytochemical reactions applied. In conclusion, the pancreatic islets of the ob+/ob+ mouse show marked differences in both morphological and immunocytochemical characteristics if compared with control littermates. These differences in architecture may be related to the eventual development of diabetes mellitus in the ob+/ob+ mouse.

Immunohistochemical and electron microscope studies of rat islets of Langerhans one month after adult thymectomy.

Ultrastructural and quantitative immunocytochemical studies of rat pancreata were carried out 1 month after adult thymectomy. The proportions of insulin-, glucagon-, and somatostatin-immunoreactive cells in the pancreas were estimated on paraffin sections using the unlabelled peroxidase-antiperoxidase method. Relative islet volume, islet size and number were determined on hematoxylin and eosin stained sections. A moderate increase of the islet volume on account of size was found in the pancreas of the thymectomized rats. The proportion of insulin-immunoreactive cells was also elevated. Ultrastructural studies showed a rich supply of secretory granules in most beta-cells. Mixed beta-endocrine-acinar cells were often observed. Mitotic figures were found in single beta-cells. The blood glucose level was in the normal range. The findings suggest a moderate stimulation of beta-cell secretory activity after thymectomy which is not associated with elevated blood glucose levels.