Discontinuous quantum and classical magnetic response of the pentakis dodecahedron.

The pentakis dodecahedron, the dual of the truncated icosahedron, consists of 60 edge-sharing triangles. It has 20 six-fold and 12 five-fold coordinated vertices, with the former forming a dodecahedron, and each of the latter connected to the vertices of one of the 12 pentagons of the dodecahedron. When spins mounted on the vertices of the pentakis dodecahedron interact according to the nearest-neighbor antiferromagnetic Heisenberg model, the two different vertex types necessitate the introduction of two exchange constants. As the relative strength of the two constants is varied the molecule interpolates between the dodecahedron and a molecule consisting only of quadrangles. The competition between the two exchange constants, frustration, and an external magnetic field results in a multitude of ground-state magnetization and susceptibility discontinuities. At the classical level the maximum is ten magnetization and one susceptibility discontinuities when the 12 five-fold vertices interact with the dodecahedron spins with approximately one-half the strength of their interaction. When the two interactions are approximately equal in strength the number of discontinuities is also maximized, with three of the magnetization and eight of the susceptibility. At the full quantum limit, where the magnitude of the spins equals12, there can be up to three ground-state magnetization jumps that have thez-component of the total spin changing by ΔSz= 2, even though quantum fluctuations rarely allow discontinuities of the magnetization. The full quantum case also supports a ΔSz= 3 discontinuity. Frustration also results in nonmagnetic states inside the singlet-triplet gap. These results make the pentakis dodecahedron the molecule with the largest number of magnetization and susceptibility discontinuities from the quantum to the classical level, taking its size also into account.

Capped carbon nanotubes with a number of ground state magnetization discontinuities increasing with their size.

The classical ground state magnetic response of fullerene molecules that resemble capped carbon nanotubes is calculated within the framework of the antiferromagnetic Heisenberg model. It is found that the magnetic response depends subtly on spatial symmetry and chirality. Clusters based on armchair carbon nanotubes which are capped with non-neighboring pentagons and have D 5d spatial symmetry have a number of magnetization discontinuities which increases with their size. This occurs even though the model completely lacks magnetic anisotropy, and even though the only source of frustration are the two groups of six pentagons located at the ends of the molecules, which become more strongly outnumbered as the clusters are filled in the middle with more unfrustrated hexagons with increasing size. For the cluster with 180 vertices there are already seven magnetization and one susceptibility discontinuities. Contrary to that, similar molecules which have D 5h spatial symmetry reach a limit of one magnetization and two susceptibility ground state discontinuities, while fullerene molecules based on zigzag carbon nanotubes and capped by neighboring pentagons also reach a fixed number of discontinuities with increasing size.

Influence of the biquadratic exchange interaction in the classical ground state magnetic response of the antiferromagnetic icosahedron.

The icosahedron has a ground state magnetization discontinuity in an external magnetic field when classical spins mounted on its vertices are coupled according to the antiferromagnetic Heisenberg model. This is so even if there is no magnetic anisotropy in the Hamiltonian. The discontinuity is a consequence of the frustrated nature of the interactions, which originates in the topology of the cluster. Here it is found that the addition of the next order isotropic spin exchange interaction term in the Hamiltonian, the biquadratic exchange interaction, significantly enriches the classical ground state magnetic response. For relatively weak biquadratic interaction new discontinuities emerge, while for even stronger the number of discontinuities for this small molecule can go up to seven, accompanied by a susceptibility discontinuity. These results demonstrate the possibility of using a small entity like the icosahedron as a magnetic unit whose ground state spin configuration and magnetization can be tuned between many different non-overlapping regimes with the application of an external field.

Thermalization of a dimerized antiferromagnetic spin chain.

Thermalization is investigated for the one-dimensional anisotropic antiferromagnetic Heisenberg model with dimerized nearest-neighbor interactions that break integrability. For this purpose the time evolution of local operator expectation values after an interacting quench is calculated directly with the Chebyshev polynomial expansion, and the deviation of the diagonal from the canonical thermal ensemble value is calculated for increasing system size for these operators. The spatial and spin symmetries of the Hamiltonian are taken into account to divide it into symmetry subsectors. The rate of thermalization is found to weaken with the dimerization parameter as the Hamiltonian evolves between two integrable limits, the non-dimerized and the fully dimerized where the chain breaks up into isolated dimers. This conclusion is supported by the distribution of the local operator off-diagonal elements between the eigenstates of the Hamiltonian with respect to their energy difference, which determines the strength of temporal fluctuations. The off-diagonal elements have a low-energy peak for small dimerization which facilitates thermalization, and originates in the reduction of spatial symmetry with respect to the non-dimerized limit. For increasing dimerization their distribution changes and develops a single low-energy maximum that relates to the fully dimerized limit and slows down thermalization.

Ground state magnetic response of two coupled dodecahedra.

The antiferromagnetic Heisenberg model on the dodecahedron possesses a number of ground state magnetization discontinuities in a field at the classical and quantum level, even though it lacks magnetic anisotropy. Here the model is considered for two dodecahedra coupled antiferromagnetically along one of their faces, as a first step to determine the magnetic response of collections of fullerene molecules. The magnetic response is determined from the competition among the intra-, interdodecahedral exchange and magnetic field energies. At the classical level the discontinuities of the isolated dodecahedron are renormalized by the interdodecahedral coupling, while new ones show up, with the maximum number of ground state discontinuities being six for a specific range of the coupling. In the full quantum limit where the individual spin magnitude [Formula: see text], there are two ground state discontinuities originating in the single discontinuity of the isolated dodecahedron, and another one due to the intermolecular coupling, generating a total of three discontinuities which come one right after the other. These results show that the magnetic response of more than one dodecahedra interacting together is quite richer than the one of a single dodecahedron.

Thermalization away from integrability and the role of operator off-diagonal elements.

We investigate the rate of thermalization of local operators in the one-dimensional anisotropic antiferromagnetic Heisenberg model with next-nearest neighbor interactions that break integrability. This is done by calculating the scaling of the difference of the diagonal and canonical thermal ensemble values as a function of system size, and by directly calculating the time evolution of the expectation values of the operators with the Chebyshev polynomial expansion. Spatial and spin symmetry is exploited and the Hamiltonian is divided into subsectors according to their symmetry. The rate of thermalization depends on the proximity to the integrable limit. When integrability is weakly broken thermalization is slow, and becomes faster the stronger the next-nearest neighbor interaction is. Three different regimes for the rate of thermalization with respect to the strength of the integrability breaking parameter are identified. These are shown to be directly connected with the relative strength of the low and higher energy difference off-diagonal operator matrix elements in the symmetry eigenbasis of the Hamiltonian. Close to the integrable limit the off-diagonal matrix elements peak at higher energies and high-frequency fluctuations are important and slow down thermalization. Away from the integrable limit a strong low-energy peak gradually develops that takes over the higher frequency fluctuations and leads to quicker thermalization.

Antiferromagnetic Heisenberg model on the icosahedron: influence of connectivity and the transition from the classical to the quantum limit.

The antiferromagnetic Heisenberg model on the icosahedron presents unconventional properties at the classical and quantum level, which originate in the frustrated nature of the interactions between the spins. Here we examine the importance of the connectivity of the icosahedron for the appearance of a magnetization discontinuity as a function of an external field which separates two families of lowest energy configurations. We also investigate the transition from the classical to the quantum limit. The influence of connectivity on the magnetic properties is revealed by considering the cluster as being made up of a closed strip of a triangular lattice with two additional spins attached. The classical magnetization discontinuity is shown to evolve continuously from the discontinuity effected by these two spins when they are uncoupled to the cluster. In the second part the transition from the classical to the quantum limit is examined by focusing on the low energy spectrum, taking fully into account the spatial and the spin symmetry of the model in the characterization of the states. A symmetry analysis of the highly degenerate lowest energy classical manifold identifies as its direct fingerprint the low energy quantum states for spin magnitude as low as s = 1, with the latter following a tower of states behavior which relates to the icosahedron having a structure reminiscent of a depleted triangular lattice. The classical character of the AHM for small s is also detected on the ground state energy and correlation functions. On the other hand the classical magnetization discontinuity in a field eventually disappears for small s, after a weak reentrant behavior.

Optical coherence tomography in bioabsorbable stents: mechanism of vascular response and guidance of stent implantation.

Fully biodegradable L-polylactic acid stents (biodegradable vascular scaffold, BVS), the latest breakthrough in the area of coronary implants, entered clinical trials in 2005 and became commercially available in 2011. Optical coherence tomography (OCT) was used from the first implants to study the vessel wall response and the timing of the resorption process in man. Analysis of BVS with OCT has several advantages over that of metallic stents. BVS polymeric struts are transparent to the light so that scaffold integrity, apposition to the underlying wall, presence of thrombus and hyperplasia, and changes in the strut characteristics over time can be easily studied. We present a comprehensive review of the findings OCT provided when used as a research tool in serial examination up to five years for investigation of the mechanism of resorption, neointimal coverage, shrinkage and late lumen enlargement. We also report our experience with OCT in 47 lesions of various complexity as a practical means of percutaneous coronary intervention guidance during BVS implantation.

Systemic lupus erythematosus complicated with pulmonary hemorrhage in a 17-year-old female.

Pulmonary hemorrhage is a rare and life-threatening complication of systemic lupus erythematosus. In this report, we described a 17-year-old female with pulmonary hemorrhage as an initial manifestation of systemic lupus erythematosus, along with lupus nephritis and central nervous system lupus. High doses of corticosteroids and pulse cyclophosphamide therapy resulted in rapid improvement of respiratory function in our patient.

[Asphyxia and intracranial hemorrhage in high-risk neonates of various gestational ages]. / Asfiksija i intrakranijalno krvarenje kod vitalno ugrozene novorodencadi razlicite gestacione dobi.

The aim of this study was to compare the type and severeness of brain damage in vitally most endangered newborn infants of different gestational age. We retrospectively analyzed the records of 75 newborn infants treated and decreased at the Department of Intensive Care and Therapy of the Institute of Children's and Adolescents' Health Care in Novi Sad. Diagnoses of hypoxic-ischemic lesion and intracranial hemorrhage in the case of grade four PVH-IVH (periventricular hemorrhage-intraventricular hemorrhage) were established by ultrasonography of the brain and lumbar punction in the case of subarachnoid hemorrhage. These diagnoses were confirmed after forensic-medical expertise. The volume and degree of the damage were compared in regard to the gestational age, Apgar score and time of initial mechanical ventilation and initial parameters of the mechanical ventilation, as well as to values of acido-basic status, concentration of gases in arterialized capillary blood and type of lung damage which always occurred in these patients. In all 75 examined newborns perinatal asphyxia was the dominant etiologic factor for the course and outcome of the disease (in all patients Apgar score was 4 or less). 75% of examines were born before 32 weeks gestation and of low or very low body weight, whereas 72% had intracranial hemorrhage (periventricular-intraventricular) and hypoxic-ischemic damage of the brain parenchyma. The rest of examinees had intracranial hemorrhage or hypoxic-ischemic damage of the brain parenchyma. Although 92% of examinees received mechanical ventilation in the first 3 days of life, only 20% of newborn infants had satisfactory values of acido-basic status and gas concentrations in the blood. We concluded that in the most severe cases of perinatal asphyxia, especially in preterm newborns of low or very low body weight, both intracranial hemorrhage and hypoxic-ischemic encephalopathy develop. Damages of other organs or systems of organs, especially lungs, as a rule contribute to infaust ending.

[Infiltration of the testes in acute lymphoblastic leukemia in childhood--personal experience]. / Infiltracija testisa u toku akutne limfoblastne leukemije decijeg uzrasta--nase iskustvo.

According to various literature data testicular leukemic infiltration occurs in 5-40%, while the mean time for testicular recurrence is 36 months. Hematologic recurrence usually occurs in the interval from 1-6 months. Although testicular leukemic infiltration clinically occurs as an isolated recurrence of leukemia, it usually presents only a clearly marked spot in the general recurrence of the disease. It is a painless enlargement of one or both testes. The diagnosis is made ultrasonographically and by histopathologic examination of the biopsied testicle tissue. This paper deals with 4 patients with acute lymphoblastic leukemia and testicular recurrence. In 2 patients the testicular recurrence occurred as a part of the general recurrence of the disease, while in the other 2 at the time of testicular recurrence diagnosis, the bone marrow was regular. All 4 patients were treated with combined radiotherapy and chemotherapy, in 3 cases successfully.

[Congenital leukemia--personal experience]. / Kongenitalna leukemija--nasa iskustva.

Congenital leukemia is a very rare form of acute leukemia and up to now more than 100 well documented cases have been published. Symptoms and signs of the disease may be faintly differentiated and be a differential diagnostic problem for a long period of time in comparison to other common diseases of the newborn. This is a case report on two newborns with congenital leukemia. It was an acute non-lymphoblastic leukemia in the first case, and acute lymphoblastic leukemia in the second. In both cases there were nonspecific manifestations of the disease (no weight gaining, hemorrhagic enterocolitis). In both cases polyhemotherapeutic protocols were performed. In the first case only partial remission occurred and death occurred during the hemathologic recidive of the disease. In the second case, 15 months after the diagnose of congenital leukemia has been established, complete remission is in course.

[Adolescent mortality in Vojvodina]. / Mortalitet adolescenata u Vojvodini.

The aim of the study was to determine the mortality rate of adolescents in Vojvodina and analyze the most common causes of their death. For the analysis we used the data from the Health Statistics Annual and from individual statistics reports. The observation period was between 1986 and 1988. The mean mortality rate of the adolescents in Vojvodina for that period was 6.7/100000. The leading cause of death (54.74%) was accidents (mostly traffic accidents), malignant diseases and finally cardiovascular diseases. The mortality rate was higher among older adolescents. It was 4 times higher in the outpatients compared to the inpatients and caused either by the severity of the injury and/or inadequately handled injuries. For the highest percentage of the accidents responsible were external factors among which risk behavior of the young played a significant role. The task of the society is to take appropriate measures which would reduce the role of the external factors as a cause of death.

[Drug poisoning in children in Vojvodina]. / Trovanje dece lekovima u Vojvodini.

Epidemiological characteristics of acute drug poisoning in children were investigated over a period of two years (1988-1989). The total number of poisonings was 450. Among causes of poisoning psychopharmaca, especially benzodiazepine, came first (33.3%). They were followed by drugs affecting the nervous system (9.1%), usually by analgoantipyretics, and by drugs affecting the cardiovascular system (7.8%). In 10.6% of the cases poisoning was due to two or more drugs. In 12.3% of the poisonings drug was unknown. Sodium fluoride was the most frequent single cause of acute poisoning. The average age of the poisoned children was 5.1 years. Poisoning with drugs was more frequent among girls than among boys (55:45%). In more than half poisoning accidents there was no one present when poisoning occurred. A major number of poisonings were an attention-getting gesture or a suicidal attempt. There were 11 cases of repeated poisoning with the same drug.

[Malignant ovarian tumors in childhood and adolescence in Novi Sad (1946-1989)]. / Maligni tumori ovarijuma u decijoj i adolescentnoj dobi u Novom Sadu (1946-1989).

In the period from 1946-1989, at the Department of Gynecology and Obstetrics University of Novi Sad, 79 ovarian tumors in children and adolescents were registered. There were 10 (12.6%) malignant tumours. The most common were dysgerminoma and carcinoma (total 6-7.6%). The treatment depended on the extent of the disease at the time of diagnosis (surgery, irradiation, chemotherapy or combination).

[Morbidity and mortality in adolescents in Vojvodina]. / Morbiditet i mortalitet adolescenata U SAP Vojvodini.

Adolescents. The aim of this study was to analyze the morbidity and mortality of adolescents in SAP Vojvodina. For the analysis, data was used from the statistical yearbooks on the health protection of the population and data from individual statistical reports. The period from 1980 to 1986 was observed. In order to more easily follow the morbidity and mortality, and for a better insight into the pathology, the adolescents were divided into 2 age groups; the younger one from 10 to 14 years of age, and the older one from 15 to 19. Adolescents in Vojvodina mostly ail from respiratory diseases, illnesses of the digestive tract, and infective diseases, but a significant role in the morbidity is also taken by injuries and poisoning. Adolescents of the age group from 10 to 14 years, get sick more often. In SAP Vojvodina 156 adolescents die annually. The highest mortality is due to injuries and poisoning (16.36/1,000,000), and after that comes the mortality due to neoplasms (5.84/1,000,000), and the diseases of the respiratory and circulatory system (3.5/1,000,000). Mortality is higher in the adolescent group from 15 to 19 years of age. With this study only a partial insight was achieved into the pathology of the adolescent age group. In order to attain a full insight, it is absolutely necessary to actively and prospectively follow the health state of adolescents and the conditions of environment.