General secondary school students' occupational health knowledge.
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Adolescent↗
Biomedical subjects
A Maris
Publications and source records attributed to A Maris.
Free-Jet Rotational Spectrum and ab Initio Calculations of Formanilide.
Formanilide has been investigated by free-jet millimeter-wave absorption spectroscopy. The rotational spectrum of the conformer with the formyl hydrogen anti to the phenyl group has been assigned. Several rotational transitions of the ground state have been measured for both normal and ND isotopic species. All the atoms of the peptidic group are coplanar to the ring. Copyright 2001 Academic Press.
Journal Article↗
Conformational equilibrium and potential energy surface of 1-fluorobutane by microwave spectroscopy and Ab initio calculations
The rotational spectra of four (GT, TT, TG, and GG) of the five possible conformers of 1-fluorobutane have been assigned by combining free jet and conventional microwave spectroscopy. The geometry optimization was performed at the MP2 (full) level of theory with the 6-31G (d) and 6-311G (d, p) basis sets and by using the B3LYP (3df, 3pd) density functional method. The relative stability of the five rotamers is calculated at the QCISD (T)/6-311G (d, p) level of theory. In spite of the fact that ab initio calculations indicated the unobserved GG' conformer to be more stable than at least one of the observed conformers it was not possible to detect its rotational spectrum. GT and TG are the most and the least stable species, respectively. The rotational spectra of several vibrational satellites of the four conformers have been studied by conventional microwave spectroscopy. The overall conformational equilibrium is governed by the two-dimensional potential energy surface of the skeletal torsions MeC-CC and FC-CC, which have been evaluated by a flexible model analysis, based on the experimental values of the relative conformational and vibrational energy spacings, and on the shifts of second moments of inertia upon conformational change and vibrational excitation. The relative energy of the fifth stable conformer (GG') was determined to be 333 cm(-1) from flexible model calculations, and to be 271 cm(-1) from the most accurate ab initio calculations.
Journal Article↗
Investigation of the Rotational Spectrum of Pyrimidine from 3 to 337 GHz: Molecular Structure, Nuclear Quadrupole Coupling, and Vibrational Satellites.
A comprehensive reinvestigation of the rotational spectrum of pyrimidine was carried out by using several different spectrometers. All singly substituted 13C- and 15N-isotopic species of pyrimidine have been measured in natural abundance with millimeter-wave free jet and waveguide Fourier transform microwave techniques, and complete rs and r0 heavy atom geometries have been determined. The ground state rotational spectrum in the centimeter-wave region was measured at sub-Doppler resolution of the cavity Fourier transform spectrometer and all elements in the inertial and principal nuclear quadrupole-coupling tensors of the nitrogen nuclei in pyrimidine have been determined. The room-temperature spectrum was measured up to 337 GHz and J = 66 with BWO-based spectrometers and sextic level centrifugal distortion constants in the rotational Hamiltonian have been determined for the ground state and three lowest vibrational fundamentals of pyrimidine. Copyright 1999 Academic Press.
Journal Article↗
Millimeter-Wave Absorption Free Jet Spectrum, Barriers to Internal Rotation, and Torsional Relaxation in p-Anisaldehyde
The rotational spectrum of p-anisaldehyde in a supersonic expansion has been investigated in the frequency range 60-78 GHz. Transitions up to J = 57 measured for the anti and syn conformers have been used to determine complete sets of fourth-order centrifugal distortion constants. Methyl group internal rotation splittings have also been observed for some of the lines and have yielded the respective barriers for both conformers. A vibrational satellite observed for each of the two conformers has been assigned to the respective first excited methoxy torsional state. The jet conditions, in particular the stagnation pressure of the carrier gas, can be adjusted to control the degree of cooling achieved in the expansion. This possibility has been exploited in the present work to enhance the intensities of the observed vibrational satellites. Applying a two-dimensional flexible model to the methoxyl and aldehydic groups torsions, the potential energy and structural deformation parameters transferred from anisole and benzaldehyde have been found to be suitable to describe these motions in p-anisaldehyde. Mixing of anti and syn conformations has been found to be insignificant within the first 82 calculated torsional eigenstates and therefore less likely to explain the intermediate bands observed in the low-resolution microwave spectrum than the internal vibrational relaxation suggested by R. K. Bohn, M. S. Farag, C. M. Ott, J. Radhakrishnan, S. A. Sorenson, and N. S. True (1992, J. Mol. Struct. 268, 107-121). A qualitative discussion of relaxation among the torsional states and its effect on the rotational spectrum is given. Copyright 1997 Academic Press. Copyright 1997Academic Press
Journal Article↗
Stress relaxation behaviour of trabecular bone specimens.
The present study defines several conditions under which stress relaxation tests can be performed and investigates the viscoelastic behaviour of trabecular bone in compression through a series of stress relaxation tests at three strain levels and in three loading directions of each cubic specimen. A viscoelastic model is proposed to characterize the behaviour of trabecular bone and a spectrum of relaxation times is determined. Trabecular bone from the femoral head is non-linearly viscoelastic and displays anisotropic behaviour, which cannot be more symmetric elastically than orthotropic.
Aged↗
A 25-kDa stretch of the extracellular domain of the human interferon gamma receptor is required for full ligand binding capacity.
We investigated which is the shortest fragment of the interferon gamma receptor with ligand binding capacity. A recombinant soluble interferon gamma receptor produced in Escherichia coli was subjected to controlled digestion with several proteolytic enzymes. The fragments generated were assayed by four approaches for interferon gamma binding. A 25-kDa polypeptide comprising residues 6-227 of the mature protein was produced by sequential digestion with trypsin and proteinase K. It was identified as the shortest receptor domain with full interferon gamma binding capacity as judged by ligand blots. The proteolytic fragments were further tested for ligand binding by interferon gamma affinity chromatography. A 15-kDa polypeptide comprising amino acids 94-227 produced by digestion with endoproteinase Glu-C was found to bind with low affinity to immobilized interferon gamma. This fragment, which does not show ligand binding capacity on protein blots, was immunoprecipitated as a complex with interferon gamma by anti-interferon gamma antibodies. It also competed for the binding of radiolabeled interferon gamma to the cell surface receptor when it was assayed as a mixture of the proteolytic products, but not after separation from the cleaved rest of the molecule. The 15-kDa polypeptide probably carries the ligand-binding domain or part of it, but it lacks sequences essential for full interferon gamma binding capacity. The stretch between amino acids 6 and 21 which does not include any disulfide bonds seems to be essential for the receptor to show full activity. The digestion with endoproteinase Glu-C revealed that cysteine residues 60 and 68 of the interferon gamma receptor form a disulfide bond.
Amino Acid Sequence↗
One interferon gamma receptor binds one interferon gamma dimer.
We investigated the stoichiometry of the interferon gamma and interferon gamma receptor interaction, using recombinant interferon gamma and recombinant soluble interferon gamma receptor, applying chemical cross-linking and chromatographic techniques, and analyzing the resulting products in denaturing polyacrylamide gels. Interferon gamma cross-linked to itself produced a major band of an apparent molecular mass of 34 kDa, which suggests that it exists as a dimer in physiological buffer and which agrees with published data. Soluble interferon gamma receptor cross-linked to itself produced mainly a 28-kDa band, suggesting that the interferon gamma receptor exists as a monomer. Interferon gamma cross-linked to the soluble interferon gamma receptor resulted in the formation of two main products of apparent molecular masses of 60 and 44 kDa. The predominant 60-kDa band resulted from the cross-linking of one interferon gamma dimer (34 kDa) to one interferon gamma receptor molecule (27 kDa). The 44-kDa band was formed by the cross-linking of one interferon gamma molecule to one interferon gamma receptor. Kinetic studies showed that the cross-linking of interferon gamma dimer to the soluble receptor proceeds through the intermediate formed by cross-linking one molecule of the interferon gamma dimer to the receptor. Reducing and dissociating agents inhibited complex formation. When chromatographed on Sephadex G-100, interferon gamma was eluted as a protein of 34-kDa molecular mass, the soluble interferon gamma receptor as a protein of 40 kDa, and their mixture was eluted in one peak corresponding to an apparent molecular mass of 73 kDa. Sodium dodecyl sulfate-polyacrylamide gel analysis of the eluted mixture showed the presence of both interferon gamma and interferon gamma receptor at a ratio of 2:1. The found results suggest that the interferon gamma receptor binds interferon gamma as a dimer.
Cell Line↗
Fibrinogen mediated activation of platelet aggregation and thromboxane A2 release: pathological implications in vascular disease.
The effect of a human fibrinogen preparation on in vitro platelet aggregation was assessed. Platelets were obtained from healthy volunteers. Human fibrinogen induced platelet aggregation in 65% of platelet rich plasma samples and enhanced submaximal platelet aggregation induced by heparin or by several conventional agonists in all samples. Aggregation induced by fibrinogen alone was reversed by the in vitro addition of human albumin. Fibrinogen induced aggregation was associated with the release of the vasoconstrictor, thromboxane A2. Preincubation with indomethacin inhibited both the aggregation and the release of thromboxane A2. Fibrinogen had no effect on in vitro vascular prostaglandin I2 synthesis (rat aortic rings) during a 60 minute incubation. The observed effects of fibrinogen on platelet function may be relevant to clinical conditions in which hyperaggregability of platelets is associated with hyperfibrinogenemia and thrombosis.
Animals↗
Burkitt's lymphoma in the base of the tongue: differential diagnosis and management.
Burkitt's lymphoma is the most common malignancy in African children but can occur sporadically in every country. It is one of the most aggressive malignancies in the human body, and in the past the prognosis was very poor. However, complex chemotherapy regimens can now cure approximately 50-80% of adult patients with Burkitt's lymphoma or small noncleaved lymphoma, and in pediatric populations the cure rate is even higher. Although the African type has a preference to the head and neck region (whereas the sporadic type to the abdomen), involvement of the base of the tongue is extremely rare as only 1 case has ever been reported in the English literature. The present study describes a patient with Burkitt's lymphoma presenting as a single mass in the base of the tongue without any abdominal or other extra-abdominal involvement. The patient was submitted to chemotherapy (intravenous and intrathecal) and skull radiotherapy. Today, 17 months after the diagnosis, the patient is disease free. Physicians should be aware of the extranodal manifestations of Burkitt's lymphoma and their differential diagnosis in order to achieve early diagnosis and treatment.
Adult↗