Showing papers by "University of Missouri published in 1991"
TL;DR: It can be concluded that arterial hypertension together with elevated circulating aldosterone are associated with cardiac fibroblast involvement and the resultant heterogeneity in tissue structure and the stage is set to prevent pathological LVH resulting from myocardial fibrosis as well as to reverse it.
Abstract: Left ventricular hypertrophy (LVH) is the major risk factor associated with myocardial failure. An explanation for why a presumptive adaptation such as LVH would prove pathological has been elusive. Insights into the impairment in contractility of the hypertrophied myocardium have been sought in the biochemistry of cardiac myocyte contraction. Equally compelling is a consideration of abnormalities in myocardial structure that impair organ contractile function while preserving myocyte contractility. For example, in the LVH that accompanies hypertension, the extracellular space is frequently the site of an abnormal accumulation of fibrillar collagen. This reactive and progressive interstitial and perivascular fibrosis accounts for abnormal myocardial stiffness and ultimately ventricular dysfunction and is likely a result of cardiac fibroblast growth and enhanced collagen synthesis. The disproportionate involvement of this nonmyocyte cell, however, is not a uniform accompaniment to myocyte hypertrophy and LVH, suggesting that the growth of myocyte and nonmyocyte cells is independent of each other. This has now been demonstrated in in vivo studies of experimental hypertension in which the abnormal fibrous tissue response was found in the hypertensive, hypertrophied left ventricle as well as in the normotensive, nonhypertrophied right ventricle. These findings further suggest that a circulating substance that gained access to the common coronary circulation of the ventricles was involved. This hypothesis has been tested in various animal models in which plasma concentrations of angiotensin II and aldosterone were varied. Based on morphometric and morphological findings, it can be concluded that arterial hypertension (i.e., an elevation in coronary perfusion pressure) together with elevated circulating aldosterone are associated with cardiac fibroblast involvement and the resultant heterogeneity in tissue structure. Nonmyocyte cells of the cardiac interstitium represent an important determinant of pathological LVH. The mechanisms that invoke short- (e.g., collagen metabolism) and long-term (e.g., mitosis) responses of cardiac fibroblasts require further investigation and integration of in vitro with in vivo studies. The stage is set, however, to prevent pathological LVH resulting from myocardial fibrosis as well as to reverse it.
2,036 citations
TL;DR: In this article, the authors examined the effect of delinquent lifestyles on the criminal victimization of teenagers and young adults and found that adolescent involvement in delinquent lifestyles strongly increases the risk of both personal and property victimization.
Abstract: Prior research on victimization in the United States has generally neglected two key areas—victimization among juveniles and young adults and the connection between offending and victimization. The research presented here fuses these two concerns by examining the effect of delinquent lifestyles on the criminal victimization of teenagers and young adults. An examination of longitudinal data from the first five waves of the National Youth Survey suggests that adolescent involvement in delinquent lifestyles strongly increases the risk of both personal and property victimization. Further, the analysis reveals that a significant proportion of the risk of victimization incurred by different demographic subgroups—especially males—results from greater involvement in lifestyles characterized by delinquency. The authors conclude that victimization patterns among youths cannot be understood apart from criminal and deviant activities.
734 citations
TL;DR: Playback experiments showed that females exhibit patterns of preferences that should result in selection that is stabilizing or weakly directional on static properties, and highly directional on dynamic properties; and the overall attractiveness of a signal is affected by variation in both static and dynamic properties.
622 citations
TL;DR: Using density-functional calculations, a three-band spinless model Hamiltonian is suggested for the description of the Verwey transition using a Stoner model as well as from calculations within the framework of the local-spin-density approximation to the density- functional theory.
Abstract: Using density-functional calculations, we examine the electronic structure of magnetite in the spinel crystal structure in order to gain insight into the nature of the Verwey transition. The calculated cohesive and magnetic properties are in agreement with experimental results. The magnetic structure is analyzed using a Stoner model as well as from calculations within the framework of the local-spin-density approximation to the density-functional theory. The calculations show a minority-spin band at the Fermi energy consisting of ${\mathit{t}}_{2\mathit{g}}$ orbitals on the Fe(B) sublattice. These results suggest a three-band spinless model Hamiltonian for the description of the Verwey transition. The hopping integrals and the electron interaction parameters entering the model Hamiltonian are calculated using the ``constrained'' density-functional theory. The calculated parameters are consistent with the electronic origin of the Verwey transition.
610 citations
TL;DR: In this article, the authors examined the relationship of career mentoring to the promotions and compensation received by 404 early career managers and professionals working in a variety of organizations and found that the relationship between mentoring and career promotion was positively correlated.
Abstract: This study examined the relationship of career mentoring to the promotions and compensation received by 404 early career managers and professionals working in a variety of organizations. The result...
525 citations
TL;DR: The results suggest that osmotic adjustment due to increased proline deposition plays an important role in the maintenance of root elongation at low water potentials.
Abstract: Seedlings of maize (Zea mays L. cv WF9 × Mo 17) growing at low water potentials in vermiculite contained greatly increased proline concentrations in the primary root growth zone. Proline levels were particularly high toward the apex, where elongation rates have been shown to be completely maintained over a wide range of water potentials. Proline concentration increased even in quite mild treatments and reached 120 millimolal in the apical millimeter of roots growing at a water potential of −1.6 megapascal. This accounted for almost half of the osmotic adjustment in this region. Increases in concentration of other amino acids and glycinebetaine were comparatively small. We have assessed the relative contributions of increased rates of proline deposition and decreased tissue volume expansion to the increases in proline concentration. Proline content profiles were combined with published growth velocity distributions to calculate net proline deposition rate profiles using the continuity equation. At low water potential, proline deposition per unit length increased by up to 10-fold in the apical region of the growth zone compared to roots at high water potential. This response accounted for most of the increase in proline concentration in this region. The results suggest that osmotic adjustment due to increased proline deposition plays an important role in the maintenance of root elongation at low water potentials.
493 citations
TL;DR: In conscious mammals including humans, the neurohumoral and hemodynamic responses to progressive acute hypovolemia have two distinct phases; there is an initial arterial baroreceptor-mediated phase in which the fall in cardiac output is nearly matched by a sympathetically mediated increase in peripheral resistance so that arterial pressure is maintained near normal levels.
Abstract: In conscious mammals including humans, the neurohumoral and hemodynamic responses to progressive acute hypovolemia have two distinct phases. There is an initial arterial baroreceptor-mediated phase in which the fall in cardiac output is nearly matched by a sympathetically mediated increase in peripheral resistance so that arterial pressure is maintained near normal levels. In most species, adrenal catecholamines and vasopressin contribute little to this phase. Increased renin release appears to augment the sympathetically mediated vasoconstriction. When blood volume has fallen by a critical amount (approximately 30%), a second phase develops abruptly. This phase is characterized by withdrawal of sympathetic vasoconstrictor drive, relative or absolute bradycardia, an increase in release of adrenal catecholamines and vasopressin, and a profound fall in arterial pressure. In rabbits and rats the signal that initiates this phase appears to travel in cardiopulmonary afferents. In dogs and humans its origin is unknown. Central opioidergic and serotonergic mechanisms may be involved.
440 citations
TL;DR: This analysis relies on linking this interval sequence to the firing-reset mechanism of real neurons, and illustrates the importance of the noise, without which sensory information cannot exist, for the transmission of sensory information.
Abstract: We discuss the two time-interval sequences which play a crucial role in studies of escape times in bistable systems driven by periodic functions embedded in noise. We demonstrate that the probability density of escape times for one of the sequences exhibits all the substantive features of experimental interspike interval histograms recorded from real, periodically forced sensory neurons. Our analysis relies on linking this interval sequence to the firing-reset mechanism of real neurons, and illustrates the importance of the noise, {ital without} {ital which} {ital the} {ital substantive} {ital features} {ital cannot} {ital exist}, for the transmission of sensory information.
430 citations
TL;DR: Interstitial fibrosis and not LVH is responsible for abnormal myocardial diastolic stiffness, whereas medical wall thickening of intramyocardial resistance vessels, influenced by arterial pressure, is associated with impaired coronary reserve.
Abstract: Left ventricular hypertrophy (LVH) in rats with genetic hypertension is accompanied by abnormal myocardial diastolic stiffness and impaired coronary reserve. Whether these functional defects are related to a structural remodeling of the myocardium that includes an interstitial and perivascular fibrosis, myocyte hypertrophy, and medial thickening of intramyocardial coronary arteries is uncertain. To address these issues, 14-week-old male spontaneously hypertensive rats with established hypertension and LVH were treated with low-dose (SLO group: 2.5 mg/kg/day, n = 11) or high-dose (SHI group: 20 mg/kg/day, n = 9) oral lisinopril for 12 weeks to sustain hypertension and LVH or to normalize arterial pressure and myocardial mass, respectively. When SHI and SLO groups were compared with age- and sex-matched 26-week-old untreated spontaneously hypertensive rats (n = 11) and normotensive Wistar-Kyoto rats (n = 9), we found 1) normalization of blood pressure (p less than 0.005) and complete regression of LVH (p less than 0.005) in the SHI group and no significant blood pressure or LVH reduction in the SLO group, 2) complete regression of morphometrically determined myocardial interstitial and perivascular fibrosis in SHI and SLO groups (p less than 0.025) associated with normalization of diastolic stiffness, measured in the isolated heart (p less than 0.025), and 3) regression of medial wall thickening of intramyocardial coronary arteries only in the SHI group (P less than 0.005), accompanied by a normalization of coronary vasodilator reserve to adenosine (p less than 0.005). Thus, interstitial fibrosis and not LVH is responsible for abnormal myocardial diastolic stiffness, whereas medical wall thickening of intramyocardial resistance vessels, influenced by arterial pressure, is associated with impaired coronary reserve.
408 citations
TL;DR: Findings call into question the assertion that the auditory mismatch detection process and the associated MMN wave are wholly independent of attentional influence and provide evidence that the processing of stimuli in unattended channels can be attenuated or gated at an early sensory level under conditions of highly focused auditory selective attention.
Abstract: The mismatch negativity (MMN) is an event-related brain potential elicited by infrequent, physically deviant sounds in a sequence of repetitive auditory stimuli. Two dichotic listening experiments that were designed to optimize the selective focusing of attention provided a strong test of Naatanen's proposal that the MMN is unaffected by attention and reflects the operation of a strongly automatic mismatch detection system. In Experiment 1, tones were presented at intervals of 120-320 ms, and the deviant tones (intensity decrements) in both the attended and unattended ears elicited negative waves consistent in waveshape, latency, and distribution with previously described MMNs. In contrast to previous reports, however, the MMN elicited by the unattended-channel deviant was markedly reduced (peak amplitude of less than 1 microV) relative to the corresponding negative wave elicited by the attended-channel deviants (3-4 microV), as well as relative to previously reported MMNs (3-6 microV) elicited by comparable deviations in stimulus intensity. In Experiment 2, which employed interstimulus intervals of 65-205 ms, the unattended-channel MMN elicited by the deviant fainter tones was barely discernible, whereas the corresponding attended-channel negativity was again about 3-4 microV. These findings call into question the assertion that the auditory mismatch detection process and the associated MMN wave are wholly independent of attentional influence. Rather, these data provide evidence that the processing of stimuli in unattended channels can be attenuated or gated at an early sensory level under conditions of highly focused auditory selective attention.
380 citations
TL;DR: There were no differences in postoperative pulmonary function, shoulder range of motion, extent of lung resection, surgical approach time, mortality, or hospital stay between the standard posterolateral and muscle-sparing thoracotomy techniques.
TL;DR: The results suggest that redox imbalance in cellular senescent systems such as the ocular lens may lead to irreversible ascorbate oxidation and protein crosslinking by xylosone, which may play an important role in the pathogenesis of "brunescent" cataracts.
Abstract: Pentosidine is a recently discovered protein crosslink, involving lysine and arginine residues linked together in an imidazo [4,5,6] pyridinium ring formed by a 5-carbon sugar during nonenzymatic browning (Maillard reaction). The presence of high ascorbate levels in the human lens and its ability to undergo nonenzymatic browning led us to investigate pentosidine formation in the aging human lens. Incubation of lens crystallins with ascorbate and its oxidation products dehydroascorbate and 2,3-diketogulonate leads progressively to the formation of pentosidine crosslinks in the presence of oxygen. Under nitrogen, however, pentosidine forms only from 2,3-diketogulonate or xylosone, a degradation product of 2,3-diketogulonate. A high correlation between pentosidine crosslinks and the degree of lens pigmentation is noted in cataractous lenses. Pentosidine is found to be primarily associated with alpha-crystallin fractions of 300-5000 kDa. These results suggest that redox imbalance in cellular senescent systems such as the ocular lens may lead to irreversible ascorbate oxidation and protein crosslinking by xylosone. This mechanism may play an important role in the pathogenesis of "brunescent" cataracts.
TL;DR: Pregnancy in cattle and sheep can be diagnosed by the presence of a conceptus-derived antigen in maternal serum that is secreted by trophoblast and placental tissue primarily as an acidic component of Mr 67,000.
Abstract: Pregnancy in cattle and sheep can be diagnosed by the presence of a conceptus-derived antigen in maternal serum that is secreted by trophoblast and placental tissue primarily as an acidic component of Mr 67,000. Molecular cloning of its cDNA reveals that the antigen belongs to the aspartic proteinase family and has greater than 50% amino acid sequence identity to pepsin, cathepsin D, and cathepsin E. The inferred sequences of the ovine and bovine polypeptides show approximately 73% identity to each other. Critical amino acid substitutions at the active site regions suggest that both proteins are enzymatically inactive. The antigen is a product of trophoblast binucleate cells that invade maternal endometrium at implantation sites.
TL;DR: It is established that IAA can be produced de novo without tryptophan as an intermediate in mutant seedlings grown on media containing stable isotopelabeled precursors.
Abstract: The maize mutant orange pericarp is a tryptophan auxotroph, which results from mutation of two unlinked loci of tryptophan synthase B. This mutant was used to test the hypothesis that tryptophan is the precursor to the plant hormone indole-3-acetic acid (IAA). Total IAA in aseptically grown mutant seedlings was 50 times greater than in normal seedlings. In mutant seedlings grown on media containing stable isotopelabeled precursors, IAA was more enriched than was tryptophan. No incorporation of label into IAA from tryptophan could be detected. These results establish that IAA can be produced de novo without tryptophan as an intermediate.
Journal Article•
TL;DR: This is the first report to substantiate an immunomodulatory role for prolactin in B/W mice and identify specific means of intervening clinically with immunosuppressive hormone-modulating therapy in SLE.
Abstract: Prolactin, an anterior pituitary hormone, stimulates humoral and cell-mediated immunity. This study investigated effects of manipulating prolactin levels in the autoimmune B/W mouse model of SLE. A group of B/W females was treated with daily injections of the prolactin-suppressing drug, bromocriptine. These mice had delayed elevation of anti-DNA antibodies and serum IgG; longevity was increased compared to control mice. Functioning syngeneic pituitary glands, implanted under the renal capsule, produced prolonged hyperprolactinemia in a separate group of female B/W mice. Hyperprolactinemic animals were characterized by premature albuminuria, elevated circulating gp70IC and IgG, and accelerated mortality. Analyses of thymic and splenic lymphocytes revealed no differences in lymphocyte subpopulations in mice with altered prolactin levels. This is the first report to substantiate an immunomodulatory role for prolactin in B/W mice. Further evaluation of this model may identify specific means of intervening clinically with immunosuppressive hormone-modulating therapy in SLE.
TL;DR: A mathematical model resulting in patient-oriented statistics that can be more easily compared with historical estimates is presented, showing that the average malignant transformation rate for an actinic keratosis is only a fraction of a percent per year.
Abstract: Dermatologists routinely treat actinic keratoses (AKs) based on the belief that these lesions are premalignant and that treatment reduces morbidity. Marks et al 1 make a convincing case for conservative management by suggesting that malignant transformation of AKs is rare and that metastasis from such transformation is uncommon. They present their data as the relationship between AKs detected during an initial visit and squamous cell carcinoma (SCC) on examination 1 year later. Using this lesion-oriented approach, Marks and colleagues 1,2 have shown that the average malignant transformation rate for an actinic keratosis is only a fraction of a percent per year. Previous clinical estimates of malignant potential ranged as high as 25% and were based on patients with several AKs followed up for many years. 3,4 Historical estimates were thus more patient oriented. We will present a mathematical model resulting in patient-oriented statistics that can be more easily compared with
TL;DR: This work considers a noisy, bistable, single neuron model in the presence of periodic external modulation, valid in the limits of weak noise intensity, weak periodic forcing and low forcing frequency, for both additive and multiplicative noise.
TL;DR: In this article, the authors derived Bayes estimators of the mean lifetime and the reliability function in the exponential life testing model and the loss functions used are asymmetric to reflect that, in most situations of interest, overestimating is more harmful than underestimating.
TL;DR: A method is given that does a better job of computing eigenvalues from the interior of the spectrum of a large matrix and a priori bounds can be given for the accuracy of interior eigenvalue and eigenvector approximations.
TL;DR: In this paper, the authors identify a methodological void in OM research as the lack of empirical theory building and propose an empirically sound model for OM theory, which is derived from the classical empirical science perspective.
Abstract: This article identifies a methodological void in operations management (OM) research as the lack of empirical theory building. It addresses two questions: What is empirical science? and How can empirical theory building be nurtured in the area? The rationale for theory building in this article is derived from the classical empirical science perspective. Further, an empirically sound model OM theory is identified and evaluated, and selected theorylike statements and informal “theories” embedded in the OM literature are classified into an accepted classification scheme made up of grand theories, middle range theories, and empirical generalizations.
TL;DR: The results indicate that theLow water potential treatment caused large changes in cell wall yielding properties that contributed to the maintenance of root elongation and the ability to adjust cell wall properties in response to low water potential may decrease with cell development.
Abstract: Spatial distributions of turgor and longitudinal growth were compared in primary roots of maize (Zea mays L. cv FR27 × FRMo 17) growing in vermiculite at high (−0.02 megapascals) or low (−1.6 megapascals) water potential. Turgor was measured directly using a pressure probe in cells of the cortex and stele. At low water potential, turgor was greatly decreased in both tissues throughout the elongation zone. Despite this, longitudinal growth in the apical 2 millimeters was the same in the two treatments, as reported previously. These results indicate that the low water potential treatment caused large changes in cell wall yielding properties that contributed to the maintenance of root elongation. Further from the apex, longitudinal growth was inhibited at low water potential despite only slightly lower turgor than in the apical region. Therefore, the ability to adjust cell wall properties in response to low water potential may decrease with cell development.
TL;DR: The multiple levels of diversity embodied in the vlp gene cluster represents a novel adaptive capability particularly suited for this class of wall‐less microbe.
Abstract: Antigenic diversity is generated in the wall-less pathogen Mycoplasma hyorhinis by combinatorial expression and phase variation of multiple, size-variant membrane surface lipoproteins (Vlps). The unusual structural basis for Vlp variation was revealed in a cluster of related but divergent vlp genes, vlpA, vlpB and vlpC, which occur as single chromosomal copies. These encode conserved N-terminal domains for membrane insertion and lipoprotein processing, but divergent external domains undergoing size variation by loss or gain of repetitive intragenic coding sequences while retaining a motif with distinctive charge distribution. Genetic analysis of phenotypically switched isogenic lineages representing ON or OFF expression states of Vlp products ruled out chromosomal rearrangement or frameshift mutations as mechanisms for Vlp phase variation. However, highly conserved vlp promoter regions contain a tract of contiguous A residues immediately upstream of the -10 box which is subject to frequent mutations altering its length in exact correspondence with the ON and OFF phase states of specific genes. This suggests a mechanism of transcriptional control regulating high frequency phase variation and random combinatorial expression of Vlps. The multiple levels of diversity embodied in the vlp gene cluster represents a novel adaptive capability particularly suited for this class of wall-less microbe.
TL;DR: The elderly group showed a performance advantage on the ability measure and for the developmental maturity of the mix of problem-solving strategies, but the young group showed an advantage for overall solution times, and a componential analysis of theOverall solution times for memory retrieval trials showed no reliable age difference for rate of retrieving addition facts from long-term memory.
Abstract: Sixty young and 60 elderly adults completed a pencil-and-paper addition test and solved 40 computer-presented simple addition problems. Strategies and problem solution times were recorded on a trial-by-trial basis and were classified in accordance with the distributions of associations model of strategy choices. The elderly group showed a performance advantage on the ability measure and for the developmental maturity of the mix of problem-solving strategies, but the young group showed an advantage for overall solution times. A componential analysis of the overall solution times for memory retrieval trials, however, showed no reliable age difference for rate of retrieving addition facts from long-term memory but did suggest that the elderly adults might have been slower than the younger adults for rate of encoding digits and verbally producing an answer. Overall results are interpreted within the context of the strategy choice model.
TL;DR: This article examined the relationship between potters' behavior in obtaining and using raw materials and the chemical composition of their finished pottery by comparing the elemental composition of ethnographic pottery and raw materials from contemporary pottery-making communities in the Valley of Guatemala.
Abstract: One of the important assumptions of compositional analysis is that the elemental composition of an artifact reflects the source of the materials used to make it. Thus, pottery from a particular source will be chemically similar to the raw materials from that source. This “commonsense” assumption seems beyond dispute, but the fact that pottery is a mixture of clay, water, and often temper added by the potter, complicates the interpretation of compositional data from ceramics. This article examines the relationship between potters' behavior in obtaining and using raw materials, on the one hand, and the chemical composition of their finished pottery, on the other, by comparing the elemental composition of ethnographic pottery and raw materials from contemporary pottery-making communities in the Valley of Guatemala. The results of this research show that the relationship between pottery and its constituent raw materials is not as obvious as was first supposed. The article concludes with an alternative approach to compositional analysis that is more in line with the realities of real-world pottery production.
TL;DR: The gene encoding the auxin-responsive GH3 mRNA from soybean was cloned, and its sequence and transcription initiation site were determined, and the auxIn-deduced GUS expression was characterized for kinetics, auxin specificity and dose response.
Abstract: The gene encoding the auxin-responsive GH3 mRNA (G. Hagen, A. Kleinschmidt, TJ. Guilfoyle, Planta 162: 147-153 (1984] from soybean was cloned, and its sequence and transcription initiation site were determined. The promoter of the GH3 gene has been fused to the open reading frame of the Escherichia coli uidA gene which encodes beta-glucuronidase (GUS). This fusion gene was introduced into tobacco via Agrobacterium tumefaciens-mediated transformation, and the expression of the gene was examined by fluorometric assay and histochemical staining of young R1 tobacco seedlings and mature plants. In transgenic tobacco plants that have not been exposed to exogenous auxin, expression of the fusion gene is largely restricted to roots of young green plants and developing floral organs, including ovules, developing seeds, and pollen, of mature plants. Application of exogenous auxin to tobacco seedlings or plant organs results in a greater than 50-fold increase in expression of GUS. Auxin-induced GUS expression is greatest in vascular tissue, but not restricted to this tissue. The auxin-deduced GUS expression was characterized for kinetics, auxin specificity and dose response.
TL;DR: Support is added for the formation of an asymmetric distribution of auxin at sites of action during tropism by constructing a chimeric gene used to transform tobacco by Agrobacterium tumefaciens.
Abstract: We constructed a chimeric gene consisting of a soybean small auxin up RNA (SAUR) promoter and leader sequence fused to an Escherichia coli [beta]-glucuronidase (GUS) open reading frame and a 3[prime] untranslated nopaline synthase sequence from Agrobacterium tumefaciens. This chimeric gene was used to transform tobacco by Agrobacterium-mediated transformation. In R2 etiolated transgenic tobacco seedlings, GUS expression occurred primarily in elongation regions of hypocotyls and roots. In green plants, GUS was expressed primarily in the epidermis and cortex of stems and petioles, as well as in elongation regions of anther filaments in developing flowers. GUS expression was responsive to exogenous auxin in the range of 10-8 to 10-3 M. During gravitropism and phototropism, the GUS activity became greater on the more rapidly elongating side of tobacco stems. Auxin transport inhibitors and other manipulations that blocked gravitropism also blocked the asymmetric distribution of GUS activity in gravistimulated stems. Light treatment of dark-grown seedlings resulted in a rapid decrease in GUS activity. Light-induced decay in GUS activity was fully reversed by application of auxin. Taken together, our results add support for the formation of an asymmetric distribution of auxin at sites of action during tropism.
TL;DR: A total of 340 cases of cutaneous neoplasia were diagnosed in 340 of 3,564 cats that were examined by biopsy or necropsy during a 41-month period from January 1, 1986 through May 31, 1989.
Abstract: A total of 340 cases of cutaneous neoplasia were diagnosed in 340 of 3,564 cats that were examined by biopsy or necropsy during a 41-month period from January 1, 1986 through May 31, 1989. Eighteen types of tumor occurred, but four types comprised 77% of the cases. These were basal cell tumor, 89 cases (26%, mean age 10.3); mast cell tumor, 72 cases (21%, mean age 8.6); squamous cell carcinoma, 52 cases (15%, mean age 11.6); and fibrosarcoma, 50 cases (15%, mean age 10.2). For each of these four types of tumors, peak number of cases occurred in cats older than 10 years. Mast cell tumor was the only tumor diagnosed in cats younger than 1 year. The head was the most common site for basal cell tumors, mast cell tumors, and squamous cell carcinomas. The legs were the most common location of fibrosarcomas. Siamese cats had approximately three times as many mast cell tumors as statistically expected, but only one-fourth as many squamous cell carcinomas. Breed predilection for other skin tumors was not apparent. Sex predilection was not detected for any skin tumor.
TL;DR: Electronic-structure calculations for Y and N give excellent results for site-dependent Fe moments, and, with spin-fluctuation theory, explain the large change in the Curie temperature on nitrogenation.
Abstract: Structural and magnetic properties of the rare-earth compounds ${\mathit{R}}_{2}$${\mathrm{Fe}}_{17}$${\mathrm{N}}_{\ensuremath{\xi}}$ have been studied with neutron-diffraction measurements and self-consistent spin-polarized electronic-structure calculations. The diffraction results indicate for the Nd compound that N goes into two sites in two or more phases of varying fractional N occupations. For the Y compound N occupies only one site. Electronic-structure calculations for ${\mathrm{Y}}_{2}$${\mathrm{Fe}}_{17}$ and ${\mathrm{Y}}_{2}$${\mathrm{Fe}}_{17}$${\mathrm{N}}_{3}$ give excellent results for site-dependent Fe moments, and, with spin-fluctuation theory, explain the large change in the Curie temperature on nitrogenation.