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Nova explosions are caused by global thermonuclear runaways triggered in the surface layers of accreting white dwarfs1–3. It has been predicted4–6that localized thermonuclear bursts on white dwarfs can also take place, similar to type-I X-ray bursts observed in accreting neutron stars. Unexplained rapid bursts from the binary system TV Columbae, in which mass is accreted onto a moderately strong magnetized white dwarf from a low-mass companion, have been observed on several occasions in the past 40 years7–11. During these bursts, the optical/ultraviolet luminosity increases by a factor of more than  three in less than an hour and fades in around ten hours. Fast outflows have been observed in ultraviolet spectral lines7, with velocities of more than 3,500 kilometres per second, comparable to the escape velocity from the white dwarf surface. Here we report on optical bursts observed in TV Columbae and in two additional accreting systems, EI Ursae Majoris and ASASSN-19bh. The bursts have a total energy of approximately 10−6times than those of classical nova explosions (micronovae) and bear a strong resemblance to type-I X-ray bursts12–14. We exclude accretion or stellar magnetic reconnection events as their origin and suggest thermonuclear runaway events in magnetically confined accretion columns as a viable explanation.

Recurring outbursts associated with matter flowing onto compact stellar remnants (such as black holes, neutron stars and white dwarfs) in close binary systems provide a way of constraining the poorly understood accretion process. The light curves of these outbursts are shaped by the efficiency of angular-momentum (and thus mass) transport in the accretion disks, which has traditionally been encoded in a viscosity parameter, α. Numerical simulations of the magneto-rotational instability that is believed to be the physical mechanism behind this transport yield values of α of roughly 0.1–0.2, consistent with values determined from observations of accreting white dwarfs. Equivalent viscosity parameters have hitherto not been estimated for disks around neutron stars or black holes. Here we report the results of an analysis of archival X-ray light curves of 21 outbursts in black-hole X-ray binaries. By applying a Bayesian approach to a model of accretion, we determine corresponding values of α of around 0.2–1.0. These high values may be interpreted as an indication either of a very high intrinsic rate of angular-momentum transport in the disk, which could be sustained by the magneto-rotational instability only if a large-scale magnetic field threads the disk, or that mass is being lost from the disk through substantial outflows, which strongly shape the outburst in the black-hole X-ray binary. The lack of correlation between our estimates of α and the accretion state of the binaries implies that such outflows can remove a substantial fraction of the disk mass in all accretion states and therefore suggests that the outflows correspond to magnetically driven disk winds rather than thermally driven ones, which require specific radiative conditions.

Context. Accretion disks in AGN should be subject to the same type of instability as in cataclysmic variables (CVs) or in low-mass X-ray binaries (LMXBs), which leads to dwarf nova and soft X-ray transient outbursts. It has been suggested that this thermal/viscous instability can account for the long-term variability of AGNs.

We consider evolutionary models for the population of short-period (Porbh) low-mass black-hole binaries (LMBHBs) and compare them with observations of soft X-ray transients (SXTs). We show that assuming strongly reduced magnetic braking (as suggested by us before for low-mass semidetached binaries) the calculated masses and effective temperatures of secondaries are encouragingly close to the observed masses and effective temperatures (as inferred from their spectra) of donor stars in short-period LMBHBs. Theoretical mass-transfer rates in SXTs are consistent with the observed ones if one assumes that accretion discs in these systems are truncated (“leaky”). We find that the population of short-period SXTs is formed mainly by systems which had unevolved or slightly evolved main-sequence donors ($M_2 \lesssim 1.2~\mbox {$M_{\odot}$}$) with a hydrogen abundance in the center $X_{\rm c} \gtrsim 0.35$at the Roche-lobe overflow (RLOF). Longer period (Porbday) SXTs might descend from systems with initial donor masses of about 1 $M_{\odot}$and $X_{\rm c} \lesssim0.35$. Thus, one can explain the origin of short period LMBHB without invoking donors with cores almost totally depleted of hydrogen. Our models suggest that, unless the currently accepted empirical estimates of mass-loss rates by winds for massive O-stars and Wolf-Rayet stars are significantly over-evaluated, a very high efficiency of common-envelope ejection is necessary to form short-period LMBHBs.

Context.Since the Fine Guiding Sensor (FGS) on the Hubble Space Telescope (HST) was used to measure the distance to SS Cyg to be $166\pm12$pc, it became apparent that at this distance the disc instability model fails to explain the absolute magnitude during outburst. It remained, however, an open question whether the model or the distance have to be revised. Recent observations led to a revision of the system parameters of SS Cyg and seem to be consistent with a distance of $d\ga\,140$pc.

The study of outer disc radius variations in close binary systems is important for understanding the structure and evolution of accretion discs. These variations are predicted by models of both quasi-steady and time-dependent discs, and these predictions can be confronted with observations. We consider theoretical and observational consequences of such variations in cataclysmic variables and low-mass X-ray binaries. We find that the action of tidal torques, that determine the outer radius at which the disc is truncated, must be important also well inside the tidal radius. We conclude that it is doubtful that the tidal-thermal instability is responsible for the superoutburst/superhump phenomena in dwarf novae, and confirm that it cannot be the reason for the outbursts of soft X-ray transients. It is likely that tidal torques play a role during superoutbursts of very-low mass-ratio systems but they cannot be the main and only cause of superhumps.

Recent observations, reported by Warner and Woudt, of Dwarf Nova Oscillations (DNOs) exhibiting frequency drift, period doubling, and 1:2:3 harmonic structure, can be understood as disc oscillations that are excited by perturbations at the spin frequency of the white dwarf or of its equatorial layers. Similar quasi-periodic disc oscillations in black hole low-mass X-ray binary (LMXB) transients in a 2:3 frequency ratio show no evidence of frequency drift and correspond to two separate modes of disc oscillation excited by an internal resonance. Just as no effects of general relativity play a role in white dwarf DNOs, no stellar surface or magnetic field effects need be invoked to explain the black hole QPOs.

We discuss the multi-wavelength predictions of the two models proposed for SU UMa stars, i.e. the enhanced mass transfer (EMT) and the tidal thermal instability (TTI) models. We focus on the systematic differences of the suggested scenarios before discussing the model predictions together with the observations of the best-studied SU UMa system, VW Hyi. We find that assuming the standard form of the viscosity parameter α, both models predict only outbursts being triggered at the inner edge of the accretion disc. In the TTI model the superoutbursts are triggered when the outer radiusof the disc reaches a certain value, i.e. the 3:1 resonance radius. In contrast, the EMT scenario predicts superoutbursts when the disc massexceeds a critical value. This causes the EMT model to be much more sensitive to mass transfer variations than the TTI model. In both models we find the predicted UV and EUV delays in agreement with the observations of VW Hyi for $\mbox{$\alpha_\mathrm{h}$}/\mbox{$\alpha_\mathrm{c}$}\la4$. In addition both models can generate precursor outbursts which are more pronounced at short wavelengths, in agreement with observations. Variations found in the observed light curve of single systems (e.g. VW Hyi) as well as the difference between ordinary SU UMa stars and ER UMa systems are a natural outcome of the EMT model while the TTI model fails to explain them.

Using XMM-Newton EPIC imaging data, we have detected 50 low-luminosity X-ray sources in the field of view of M 22, where $5\pm3$of these sources are likely to be related to the cluster. Using differential optical photometry, we have identified probable counterparts to those sources belonging to the cluster. Using X-ray spectroscopic and timing studies, supported by the optical colours, we propose that the most central X-ray sources in the cluster are cataclysmic variables, millisecond pulsars, active binaries and a blue straggler. We also identify a cluster of galaxies behind this globular cluster.

We show that the recently developed thermal model which successfully describes how jets are launched by young stellar objects, when applied to system containing disk-accreting white dwarfs naturally explain the otherwise surprising absence of jets in cataclysmic variable stars. Our main argument uses the crucial element of the thermal model, namely that the accreted material is strongly shocked due to large gradients of physical quantities in the boundary layer, and then cools on a time scale longer than its ejection time from the disk. In our scenario the magnetic fields are weak, and serve only to recollimate the outflow at large distances from the source, or to initiate the shock, but not as a jet-driving agent. Using two criteria in that model, for the shock formation and for the ejection of mass, we find the mass accretion rate above which jets could be blown from accretion disks around young stellar objects and white dwarfs. We find that these accretion mass rates are $\dot M ({\rm YSO}) \ga 10^{-7}~ M_\odot ~\rm{yr}^{-1}$and $\dot M ({\rm WD}) \ga 10^{-6}~ M_\odot ~\rm{yr}^{-1}$for young stellar objects and white dwarfs respectively. Considering the uncertainties of the model, these limits could overestimate the critical value by a factor of ∼10.

Using the disc instability model and a simple but physically reasonable model for the X-ray, extreme UV, UV and optical emission of dwarf novae we investigate the time lags observed between the rise to outburst at different wavelengths. We find that for “normal”, i.e. fast-rise outbursts, there is good agreement between the model and observations provided that the disc is truncated at a few white dwarf radii in quiescence, and that the viscosity parameter ais ~0.02 in quiescence and ~0.1 in outburst. In particular, the increased X-ray flux between the optical and EUV rise and at the end of an outburst, is a natural outcome of the model. We cannot explain, however, the EUV delay observed in anomalous outbursts because the disc instability model in its standard a-prescription form is unable to produce such outbursts. We also find that the UV delay is, contrary to common belief, slightly longer for inside-out than for outside-in outbursts, and that it is not a good indicator of the outburst type.

We show that the absence of outbursts during low states of VY Scl stars is easily explained if white dwarfs in these systems are weakly magnetized ($\mu\gtrsim 5\times 10^{30}$G cm3). However, some of the VY Scl stars are observed to have very slow declines to minimum and similarly slow rises to maximum. The absence of outbursts during such intermediate(as opposed to low) states, which last much longer than typical disc viscous times, can be explained only if accretion discs are absent when their temperatures would correspond to an unstable state. This requires magnetic fields stronger than those explaining outburst absence during low states, since white dwarfs in this sub-class of VY Scl stars should have magnetic moments $\mu\gtrsim 1.5\times 10^{33}$G cm3i.e. similar to those of Intermediate Polars. Since at maximum brightness several VY Scl stars are SW Sex stars, this conclusion is in agreement with recent claims about the magnetic nature of these systems.

We study the prospect of explaining the outbursts of Soft X-ray Transients (SXTs) by the thermal-viscous instability in a thin disc. This instability is linked to hydrogen ionization and is significantly changed when irradiation of the disc by X-rays from the inner regions is included. We present the first numerically reliable, physically consistent calculations of the outburst cycles which include the effects of accretion disc irradiation. The decay from outburst is governed by irradiation, as pointed out by King & Ritter (1998), leading to slow exponential decays. At the end of the outburst, the disc is severely depleted, which lengthens the time needed to rebuild mass to the critical density for an outburst. Despite this, the long recurrence times and quiescent X-ray luminosities of SXTs still require the inner disc to be replaced by another type of flow in quiescence, presumably a hot advection dominated accretion flow (ADAF). We include the effects of such truncation and show that the resulting lightcurves are conclusively similar to those of SXTs like A0620-00. We conclude that the two-αdisc instability model provides an adequate description of the outbursts of SXTs when both truncation and irradiation are included. The values for the viscosities in outburst and in quiescence are comparable to those used in CVs. We discuss the model in the context of present observations.

We show that the disc instability model can reproduce all the observed properties of Z Cam stars if the energy equation includes heating of the outer disc by the mass-transfer stream impact and by tidal torques and if the mass-transfer rate from the secondary varies by about $30\%$around the value critical for stability. In particular the magnitude difference between outburst maxima and standstills corresponds to observations, all outbursts are of the inside-out type and can be divided into two classes: long (wide) and short (narrow) outbursts, as observed. Mass transfer rate fluctuations should occur in other dwarf novae but one can exclude variations similar to those observed in magnetic systems (AM Her's and some DQ Her's) and some nova-like systems (VY Scl's), in which $\dot{M}$become very small during low states; these would produce mini-outbursts which, although detectable, have never been observed.

We show that if the dwarf-nova disc instability model includes the effects of heating by stream impact and tidal torque dissipation in the outer disc, the calculated properties of dwarf-nova outbursts change considerably, and several notorious deficiencies of this model are repaired. In particular: (1) outside-in outbursts occur for mass transfer rates lower than in the standard model as required by observations; (2) the presence of long (wide) and short (narrow) outbursts with similar peak luminosities is a natural property of the model. Mass-transfer fluctuations by factors ∼2 can explain the occurrence of both long and short outbursts above the cataclysmic variable period gap, whereas below 2 hr only short normal outbursts are expected (in addition to superoutbursts which are not dealt with in this article). With additional heating by the stream and tidal torques, such fluctuations can also explain the occurrence of both outside-in and inside-out outbursts in SS Cyg and similar systems. The occurrence of outside-in outbursts in short orbital-period, low mass-transfer-rate systems requires the disc to be much smaller than the tidal-truncation radius. In this case the recurrence time of both inside-out and outside-in outbursts have a similar dependence on the mass-transfer rate $\dot{M}_{2}$.

In the case involving particles, the necessary and sufficient condition for the Penrose process to extract energy from a rotating black hole is absorption of particles with negative energies and angular momenta. No torque at the black-hole horizon occurs. In this article we consider the case of arbitrary fields or matter described by an unspecified, general energy-momentum tensor Tμν and show that the necessary and sufficient condition for extraction of a black hole's rotational energy is analogous to that in the mechanical Penrose process: absorption of negative energy and negative angular momentum. We also show that a necessary condition for the Penrose process to occur is for the Noether current (the conserved energy-momentum density vector) to be spacelike or past directed (timelike or null) on some part of the horizon. In the particle case, our general criterion for the occurrence of a Penrose process reproduces the standard result. In the case of relativistic jet-producing "magnetically arrested disks," we show that the negative energy and angular-momentum absorption condition is obeyed when the Blandford-Znajek mechanism is at work, and hence the high energy extraction efficiency up to ~300% found in recent numerical simulations of such accretion flows results from tapping the black hole's rotational energy through the Penrose process. We show how black-hole rotational energy extraction works in this case by describing the Penrose process in terms of the Noether current. [ABSTRACT FROM AUTHOR]

For thermonuclear flashes to occur on neutron-star surfaces, fuel must have been accreted from a donor star. However, sometimes flashes are seen from transient binary systems when they are thought to be in their quiescent phase, during which no accretion, or relatively little, is expected to occur. We investigate the accretion luminosity during several such flashes, including the first-ever and brightest detected flash from Cen?X-4 in 1969. We infer from observations and theory that immediately prior to these flashes the accretion rate must have been between about 0.001 and 0.01?times the equivalent of the Eddington limit, which is roughly 2?orders of magnitude less than the peak accretion rates seen in these transients during an X-ray outburst and 3?4?orders of magnitude more than the lowest measured values in quiescence. Furthermore, three such flashes, including the one from Cen?X-4, occurred within 2 to 7?days followed by an X-ray outburst. A long-term episode of enhanced, but low-level, accretion is predicted near the end of the quiescent phase by the disk-instability model, and may thus have provided the right conditions for these flashes to occur. We discuss the possibility of whether these flashes acted as triggers of the outbursts, signifying a dramatic increase in the accretion rate. Although it is difficult to rule out, we find it unlikely that the irradiance by these flashes is sufficient to change the state of the accretion disk in such a dramatic way.

Context. Stellar companions of accreting neutron stars in ultra compact X-ray binaries (UCXBs) are hydrogen-deficient. Their helium or C/O accretion discs are strongly X-ray irradiated. Both the chemical composition and irradiation determine the disc stability with respect to thermal and viscous perturbations. At shorter periods, UCXBs are persistent, whereas longer-period systems are mostly transient.Aims. To understand this behaviour one has to derive the stability criteria for X-ray irradiated hydrogen-poor accretion discs.Methods. We use a modified and updated version of the Dubus et?al. code describing time-dependent irradiated accretion discs around compact objects.Results. We obtained the relevant stability criteria and compared the results to observed properties of UCXBsConclusions. Although the general trend in the stability behaviour of UCXBs is consistent with the prediction of the disc instability model, in a few cases the inconsistency of theoretical predictions with the system observed properties is weak enough to be attributed to observational and/or theoretical uncertainties. Two systems might require the presence of some amount of hydrogen in the donor star.

Heyl (2000) made an interesting suggestion that the observed shifts in QPO frequency in type I X-ray bursts could be influenced by the same geometrical effect of strong gravity as the one that causes centrifugal force reversal discovered by Abramowicz & Lasota (1974). However, his main result contains a sign error. Here we derive the correct formula and conclude that constraints on the $M(R)$relation for neutron stars deduced from the rotational-modulation model of QPO frequency shifts are of no practical interest because the correct formula implies a weak condition $R_* > 1.3 R_{\rm S}$, where RSis the Schwarzschild radius. We also argue against the relevance of the rotational-modulation model to the observed frequency modulations.

We present results of a population synthesis study for semidetached short orbital period binaries which contain low-mass (?1.5M?) donors and massive (? 4M?) compact accretors, which in our model represent black holes. Evolution of these binaries is determined by nuclear evolution of the donors and/or orbital angular momentum loss due to magnetic braking by the stellar wind of the donors and gravitational wave radiation. According to our model the estimated total number of this type of black-hole binaries in the Galaxy is ? 10000. If the magnetic braking removing angular momentum in semidetached black-hole binaries is described by the Verbunt & Zwaan formula, the model predicts that among them around 3000?systems with periods >2?h would be transient. In addition one finds several hundreds of luminous and stable systems with periods between?3 and 8?h. Several dozens of these bright systems should be observed above the RXTE ASM sensitivity limit. The absence of such systems implies that upon Roche-lobe overflow by the low-mass donor angular momentum losses are reduced by a factor more than?2 with respect to the Verbunt & Zwaan prescription. In such a case short period black-hole soft X-ray transients (SXT) may have donors that overflow the Roche lobe in the core hydrogen-burning stage. We show that it is unlikely that the transient behaviour of black-hole short-period X-ray binaries is explained by the evolved nature of the stellar companion. On the other hand a substantial fraction of black-hole binaries with periods >3?h could be faint with truncated, stable cold accretion discs as proposed by Menou et al. Most of the semidetached black-hole binaries are expected to have periods shorter than ~2?h. Properties of such, still to be observed, very small mass-ratio (q=M2/M1 < 0.02) binaries are different from those of their longer period cousins.?

Gastrointestinal stromal tumors (GIST), KIT-positive and KIT signaling driven or platelet-derived growth factor receptor α (PDGFRA) signaling driven mesenchymal tumors, are poorly known in nonhuman primates. Availability of KIT- and PDGFRA-inhibitor drug imatinib mesylate has greatly raised the interest for these tumors. At necropsy of a 22-year-old male chimpanzee, a round, firm 2-cm intramural tumor was incidentally found in the midbody of the stomach and diagnosed as a GIST. Histologically, the mass was composed of spindle to polygonal epithelioid cells arranged in short to intermediate-length, interlacing streams, bundles, and nodular whorls often separated by hyalinized eosinophilic matrix. The mitotic rate was a maximum 1/50 high-power field. Immunohistochemically, the tumor cells were diffusely positive for KIT and CD34, focally positive for α-smooth muscle actin, and negative for muscle specific actin, desmin, S-100 protein, synaptophy-sin, and glial fibrillary acidic protein. Because the majority of human GISTs have gain-of-function KIT or PDGFRA mutations, genomic sequences of KIT exons 9, 11, 13, and 17 and PDGFRA exons 12 and 18 from this chimpanzee GIST were polymerase chain reaction amplified and sequenced. However, no mutation was identified in the analyzed “mutational hot spots.” This study is the first extensive histomorphologic, immunohistochemical, and molecular genetic analysis of a chimpanzee GIST. More cases of nonhuman primate GISTs should be analyzed to discover the clinicopathologic spectrum of GISTs in these species.

Fifty canine gastrointestinal (GI) mesenchymal tumors were examined to determine the occurrence of leiomyomas (LM) and GI stromal tumors and to compare their clinicopathologic features. Twenty-one tumors (42%) were histologically reclassified as gastrointestinal stromal tumors (GISTs) and 29 tumors (58%) as LMs on the basis of their histologic similarity with homologous human tumors. The GISTs occurred equally in males and females, with a mean age of 11 years (range 5–14 years). Five GISTs (24%) were associated with clinical signs and six (29%) had metastasis in liver or abdominal cavity. The GISTs occurred in large intestine (10, 48%), small bowel (six, 29%), stomach (four, 19%), and mesentery of small intestine (one, 5%). Histologically, they were highly cellular spindle, or less commonly epithelioid tumors with mitotic rates ranging from 0 to 19 per 10 HPF. Eleven tumors (52%) were positive for CD117 (KIT); seven (33%) were positive for smooth muscle actin but none for desmin and S-100 protein. Sequences of KIT exon 11, often mutated in human GISTs, were evaluated from four GISTs. Deletion of Try556-Lys557coexisting with duplication of Gln555in one case of GIST and T to C transition resulting in substitution of Pro for Leu575in another were identified. The LMs occurred predominantly in males (82%) with a mean age of 11 years (range 8–17 years). Nine tumors (31%) had associated clinical signs. They occurred in the stomach (22, 76%), esophagus (four, 14%), and intestines (three, 10%); all were paucicellular, had no mitoses, and were composed of mature smooth muscle cells. Twenty-eight (97%) were positive for smooth muscle actin and 18(62%) for desmin but none for CD117 and S-100. Both GISTs and true LMs occur in the GI tract of dogs. Both tumors have distinctive pathologic features.

Recently, several ways of verifying the existence of black-hole horizons have been proposed. We show here that most of these suggestions are irrelevant to the problem of the horizon, at best they can rule out the presence of conventional baryonic matter in the outer layers of black-hole candidates. More generally, we argue that it is fundamentally impossible to detect in electromagnetic radiation direct evidence for the presence of a black-hole horizon. This applies also to future observations, which would trace very accurately the details of the space-time metric of a body suspected of being a black hole. Specific solutions of Einsteins's equations lack an event horizon, and yet are indistinguishable in their electromagnetic signature from Schwarzschild black holes.

Abstract: Testicular lymphomas usually occur in older men and are mostly diffuse large B-cell lymphomas (DLBL). They may be primary manifestation of lymphoma or represent a relapse of a previous non-Hodgkin’s lymphoma. This report details a testicular large cell lymphoma, which was proven to be large cell transformation of a low-grade follicular lymphoma biopsied 8 years earlier. Initially, a 38-year old man was diagnosed with cervical lymphadenopathy, and biopsy was interpreted as reactive follicular hyperplasia; no treatment was given, and the lymphadenopathy resolved spontaneously. Eight years later, the patient underwent surgery for a left testicular mass and gastroscopy for gastric symptoms. The patient died 7 months later with evidence for intra-abdominal and central nervous system lymphoma after a brief but temporary response to M-BACOD chemotherapy. Orchiectomy specimen and gastroscopic biopsy showed diffuse large B-cell lymphoma (CD20+), which infiltrated between well-preserved tubules in the testis. Histological comparison with 20 testicular lymphomas without previous lymphoma showed tubule infiltration in all cases, suggesting that the tubule-preserving infiltration pattern could be a histological marker for secondary lymphoma involvement in testis. On re-examination, the lymph node 8 years prior was verified as follicular, predominantly small, cleaved cell lymphoma with bcl2-positive follicles. The earlier follicular lymphoma and the subsequent diffuse large cell lymphoma were analyzed using polymerase chain reaction and showed identical sequences of the t(14;18) translocation and immunoglobulin heavy chain gene rearrangement. Analysis of the VH-gene sequences from the follicular lymphoma revealed sequence heterogeneity consistent with ongoing mutation. However, the transformed diffuse large cell lymphoma had no intraclonal variation, with the sequence matching with one of the subclones from the low-grade follicular lymphoma. These results confirm that the large cell transformation of follicular lymphoma occurs in a single follicular lymphoma cell. This case also indicates that the selection of the transformed clone can be part of the natural history of disease and can occur without exposure to chemotherapy.

We investigate whether models based on the assumption that jets in quasars are powered by rotating black holes can explain the observed radio dichotomy of quasars. We show that in terms of the ‘spin paradigm’ models, radio‐loud quasars could be objects in which the rotation rate of the black hole corresponds to an equilibrium between spin‐up by accretion and spin‐down by the Blandford–Znajek mechanism. Radio‐quiet quasars could be hosting black holes with an average spin much smaller than the equilibrium one. We discuss possible accretion scenarios which can lead to such a bimodal distribution of black hole spins.

The receptor protein tyrosine phosphatase γ gene, PTPγ (locus namePTPRG), was previously mapped to chromosome region 3p14.2, within a 2- to 4-Mb region centromeric to the 3p14.2 breakpoint of the t(3;8) familial renal cell carcinoma (RCC)-associated constitutional chromosome translocation. Because of its chromosomal position, its enzymatic properties as a receptor phosphatase, which might oppose a growth activating kinase activity, its homozygous deletion in murine L cells, and its transcriptional activity in numerous normal tissues, including kidney, the PTPγ gene was an attractive tumor suppressor gene candidate for renal cell carcinoma. To determine whether the PTPγ gene was a target of loss of heterozygosity or mutation in RCCs and to determine its map position relative to the t(3;8) break at 3p14.2, we have isolated YAC and λ genomic clones for the PTPγ gene and other 3p14.2 markers and determined the relative positions of the t(3;8) break, a 3p14.2de novobreak possibly in a fragile site, and the 5′ end of the PTPγ gene. Additionally, the genomic structure, position of the proximal promotor, and intron–exon border sequences of the 30-exon ∼780-kb PTPγ gene have been determined, which will facilitate analysis of the PTPγ gene in tumors.

We discuss the arguments in favour of the suggestion that polars (AM Her systems) and intermediate polars (IP's) have magnetic fields of the same order of magnitude, and form one single class of objects. The period distribution of magnetic catclysmic variables is well explained if they evolve the same way as non magnetic systems, IP's becoming AM Her systems after crossing the gap. We discuss some consequences of the limited magnetic moment distribution (1033=µ=1034 G cm-3) in magnetic CV's, in particular for the existence of accretion discs in those systems.

G protein-coupled receptor kinases (GRKs) play an important role in phosphorylating and regulating the activity of a variety of G protein-coupled receptors. Chromosomal mapping of the human genes for the two most recently identified members of the GRK family, GRK5 (GPRK5) and GRK6 (GPRK6), was accomplished by correlation of the presence of the GPRK5 and GPRK6 loci with specific chromosome regions in a rodent-human hybrid panel. These analyses revealed that GPRK5 maps to chromosome region 10q24→qter while GPRK6 maps to 5q35. A GPRK6 related locus maps to 13pter→q21.

Some inequalities have to be satisfied if there is to exist a fluid source for a given exterior gravitational field. In the case of the Kerr solution one of the inequalities presented here is much more restrictive than those obtained by Boyer [1]. However, our conditions do not exclude the possibility of a fluid source for the Kerr spacetimes.

Attention is drawn to the advantages of representing dynamical behavior in a stationary or static background spacetime in terms of a fixed reference 3-geometry that differs from the usual one by a certain conformal rescaling factor. The resulting Riemannian metric may be appropriately described as the “optical geometry” in recognition of the fact that “line-of-sight” trajectories are faithfully represented within it as geodesic, at least in the strictly static case for which such “lines-of-sight” are unambiguously defined. (In more general stationary examples the geodesies represent what amounts to the result of a cancellation between the Coriolis-type effects that would cause a physical light path to deviate to one side or the other depending on the sense of propagation.) The application to the particular case of the Schwarzschild solution is discussed: In this example the optical 3-geometry has a throat that occurs not on the horizon (as in the directly projected 3-geometry) but at the radius of the circular null geodesic orbit.

Report on the Nordita Workdays on Quasi-Peridic Oscillations (QPOs). (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The spectra of more than 20 γ-ray bursts show dips in the 30–70 keV range1–3, that have been interpreted as cyclotron absorption lines1,2. The presence of these absorption lines, is one of the arguments in support of the belief that γ-ray bursts originate from neutron stars with very strong (1012–1013G) magnetic fields1. This interpretation, however, poses serious problems4–6; for example, if the continuum is produced by optically-thin thermal cyclotron radiation it implies a magnetic field increasing with the distance from the surface of a neutron star5. Here we propose a different interpretation of the dips in the spectra of γ-ray bursts. We show that these dips could result from a superposition of two spectra: an optically thin thermal synchrotron spectrum with an (observed) turnover at about 55–110 keV and a softer one that is best fitted with a black body. We find black-body temperatures in the range of 7–12 keV. Due to poor statistics and the uncertain quality of the data7our results should be considered only as tentative, our main objective is to point out that using a two-component interpretation for the dips in γ-ray bursts spectra could confirm the synchrotron mechanism.

Quasi-periodic millisecond oscillations in the X-ray flux of two low-mass X-ray binaries, GX5–1 and ScoX-1, were recently reported1–4. These quasi-periodic fluctuations are very similar to those observed in the soft X-ray flux of some dwarf novae in outburst5,6. Guided by this analogy, we propose here that, as in the case of dwarf novae7, oscillations in low-mass X-ray binaries are caused by transient magnetic fields generated by turbulent dynamo action in the boundary layer and possibly in the corona of the accreting neutron star. The magnetic fields created in this way are too weak to channel the accreting material, but are strong enough to influence the heat transport in the neutron star corona and boundary layer and to cause bright spots with lifetimes of a few rotation periods to appear randomly on the neutron star surface. The rotation of this star's outer layers, together with the appearance and disappearance of the spots at random azimuthal positions, then gives rise to oscillations with the coherence characteristics reported in the observations.

Here we aim to point out the rather stringent limitations, particularly those due to frequency stability requirements, that can be placed on conceivable (for example, binary) sources of any gravitational waves that might be detected by resonant stimulation of an oscillation mode in the Solar System. This question has recently been raised by widespread informal discussions1,2of the possibility that unexpectedly persistent low-frequency (160-min period) oscillations observed in the Sun3might be due to such a mechanism4. We show here that this particular possibility can be excluded.

We study the process of spinning up black holes by accretion from slim disks for a wide range of accretion rates. We show that for super-Eddington accretion rates and low values of the viscosity parameter α( ≲ 0.01) the limiting value of the dimensionless spin parameter a∗can reach values higher than a∗= 0.9978 inferred by Thorne in his seminal study. For Ṁ= 10   ṀEddand α= 0.01, spin equilibrium is reached at a∗= 0.9994. We show that the equilibrium spin value depends strongly on the assumed value of α. We also prove that for high accretion rates the impact of captured radiation on spin evolution is negligible.

We report on a scheme for incorporating vertical radiative energy transport into a fully relativistic, Kerr-metric model of optically thick, advective, transonic alpha disks. Our code couples the radial and vertical equations of the accretion disk. The flux was computed in the diffusion approximation, and convection is included in the mixing-length approximation. We present the detailed structure of this “two-dimensional” slim-disk model for α= 0.01. We then calculated the emergent spectra integrated over the disk surface. The values of surface density, radial velocity, and the photospheric height for these models differ by 20%–30% from those obtained in the polytropic, height-averaged slim disk model considered previously. However, the emission profiles and the resulting spectra are quite similar for both types of models. The effective optical depth of the slim disk becomes lower than unity for high values of the alpha parameter and for high accretion rates.

The “radiation inner edge” of an accretion disk is defined as the inner boundary of the region from which most of the luminosity emerges. Similarly, the “reflection edge” is the smallest radius capable of producing a significant X-ray reflection of the fluorescent iron line. For black hole accretion disks with very sub-Eddington luminosities these and all other “inner edges” coexist at the innermost stable circular orbit (ISCO). Thus, in this case, one may rightly consider ISCO as the unique inner edge of the black hole accretion disk. However, even at moderate luminosities, there is no such unique inner edge because differently defined edges are located at different places. Several of them are significantly closer to the black hole than ISCO. These differences grow with the increasing luminosity. For nearly Eddington luminosities, they are so huge that the notion of the inner edge loses all practical significance.

Context. Radiation from accretion discs in cataclysmic variable stars (CVs) provides fundamental information about the properties of these close binary systems and about the physics of accretion in general. Of particular interest are dwarf-nova outburst cycles during which variations of the disc properties allow a detailed study of the physical processes in accretion flows.Aims. The detailed diagnostics of accretion disc structure can be achieved by including in its description all the relevant heating and cooling physical mechanism, in particular the convective energy transport that, although dominant at temperatures ≲104K, is usually not taken into account when calculating spectra of accretion discs. The disc's self-consistently calculated structure and emission allow testing models of dwarf-nova outbursts and accretion-disc models in general.Methods. We constructed a radiative transfer code coupled with a code determining the disc's hydrostatic vertical structure.Results. We have obtained for the first time a model spectra of cold, convective accretion discs. As expected, these spectra are mostly flat in the optical wavelengths with no contribution from the UV, which in quiescence must be emitted by the white dwarf. The disc structures obtained with our radiative-transfer code compare well with the solutions of equations used to describe the dwarf-nova outburst cycle according to the thermal-viscous disc instability model thus allowing the two to be combined. For high-temperature radiative discs our spectra are compatible with models obtained with Hubeny's code TLUSTY.Conclusions. Our code allows calculating the spectral evolution of dwarf nova stars through their whole outburst cycle, providing a new tool for testing models of accretion discs in cataclysmic variables. We show that convection plays an important role in determining the vertical disc structure and substantially affects emitted spectra when, as often the case, it is effective at optical depths τ~ 1. The emergent spectrum is independent of the parameters of the convection model. We confirm that, as required by the disc instability model, quiescent discs in dwarf novae must be optically thick in their outer regions. In general, no emission lines are present in the absence of external irradiation.

Effects of methomyl, permethrin, and fenvalerate residues were tested in the laboratory on adult Pteromalus puparum (L.), a gregarious pupal parasite of the imported cabbageworm, Artogeia rapae (L.). Survival of adult female parasites exposed to the insecticides did not differ from that of untreated controls. However, significantly more males died compared with controls following exposure to methomyl for 12 h and for 6 days.

The susceptibility of diamondback moth, Plutella xylostella (L.), larvae to 2 avermectins, abamectin and MK-243 (4"-ei-methylamino-4" deoxyavermectin B1 hydrochloride), was assessed through toxicity evaluations of 17-19 geographically diverse populations. Both avermectins were very potent to 3rd-instar diamondback moth; LC50s for abamectin and MK-243 ranged from 0.4 to 44.0 ng (AI)/ml and 0.2 to 8.0 ng (AI)/ml, respectively. Although most populations showed resistance to methomyl and permethrin, the populations were not resistant to abamectin or MK-243. Pairwise correlations indicated lack of cross or multiple resishmce between the avermectins and methomyl and permethrin. This information will serve as an aid for resistance monitoring programs and permit comparative changes in susceptibility during commercial use. Such data are necessary to assist in decisions to recommend product use appropriately in the context of resistance management.

The residual contact toxicity of MK-243 (4"-epi-methylamino-4"-deoxyavermectin B1 hydrochloride), permethrin, esfenvalerate (pyrethroids) and methomyl (carbamate) to 2 parasitic hymenoptera, Cotesia orobenae (L.) (Braconidae) and Pteromalus puparum (L.) (Pteromalidae), in broccoli was evaluated. Each parasite was caged on treated broccoli leaves at various times after the plants had been sprayed in the field. Methornyl was the only insecticide consistently toxic to P. puparum up to 1 d after the leaves were sprayed, but this compound had no affect 3 d after treatment. MK-243 and the 2 pyrethroids had no significant effect on P. puparum. The effect of the insecticides on C. orobenae was different and less consistent. Esfenvalerate caused significant mortality of C. orobenae, but methomyl and permethrin killed a significant number of parasites in only 1 of the 2 trials. MK-243 was not toxic to C. orobenae in our studies.

Pteromalus puparum (L.) parasitized 64.1 and 32.5% of imported cabbageworm, Artogeia rapae (L.), pupae collected from pesticide-free cabbage field plots in 1983 and 1984, respectively, in southwestern Virginia. Parasitism was most pronounced in the latter part of the season. In commercial cabbage fields, 67.2% of overwintering pupae were parasitized. High percentages of parasites successfully emerged as adults, indicating efficient host utilization. Most parasite mortality within the host occurred in the larval stage; mean adult parasite emergence per host for 1983 and 1984 was 52.3, with a 1:1 sex ratio. However, variability of male parasites per host was double that of females. Females weighed twice as much as males, suggesting a compensation of number for size. P. puparum did not parasitize either host sex discriminately, and equal numbers of male and female parasites emerged from both host sexes. Laboratory studies suggest that host/parasite ratios and length of host/parasite exposure time are important considerations for laboratory rearing of P. puparum. Suboptimal conditions result in unparasitized and mutilated hosts.