350 research outputs found
Self-similar structure of a hot magnetized flow with thermal conduction
We have explored the structure of hot magnetized accretion flow with thermal
conduction. The importance of thermal conduction in hot accretion flows has
been confirmed by observations of the hot gas surrounding Sgr and a few
other nearby galactic nuclei. For a steady state structure of such accretion
flows a set of self similar solutions are presented. In this paper, we have
actually tried to re-check the solution presented by Abbassi et al. (2008)
using a physical constrain. In this study we find that Eq 29 places a new
constrain that limits answers presented by Abbassi et al. 2008. In that paper
the parameter space in which it is established in the new constrain was
plotted. However, the new requirement makes up only a small parameter space
with physically acceptable solutions. And now in this manuscript we have
followed the idea with more effort, and tried to find out how thermal
conduction influences the structur of the disks in a physical parameter space.
We have found out that the existence of thermal conduction will lead to
reduction of accretion and radial and azimuthal velocities as well as the
vertical thickness of the disk, which is slightly reduced. Moreover, the
surface density of the disk will increase when the thermal conduction becomes
important in the hot magnetized flow.Comment: Accepted for publication, AP
Prime ideals in nilpotent Iwasawa algebras
Let G be a nilpotent complete p-valued group of finite rank and let k be a
field of characteristic p. We prove that every faithful prime ideal of the
Iwasawa algebra kG is controlled by the centre of G, and use this to show that
the prime spectrum of kG is a disjoint union of commutative strata. We also
show that every prime ideal of kG is completely prime. The key ingredient in
the proof is the construction of a non-commutative valuation on certain
filtered simple Artinian rings
Resistive and magnetized accretion flows with convection
We considered the effects of convection on the radiatively inefficient
accretion flows (RIAF) in the presence of resistivity and toroidal magnetic
field. We discussed the effects of convection on transports of angular momentum
and energy. We established two cases for the resistive and magnetized RIAFs
with convection: assuming the convection parameter as a free parameter and
using mixing-length theory to calculate convection parameter. A self-similar
method was used to solve the integrated equations that govern the behavior of
the presented model. The solutions showed that the accretion and rotational
velocities decrease by adding the convection parameter, while the sound speed
increases. Moreover, by using mixing-length theory to calculate convection
parameter, we found that the convection can be important in RIAFs with magnetic
field and resistivity.Comment: 7 pages, 3 figures, accepted by Ap&S
Vertically Self-Gravitating ADAFs in the Presence of Toroidal Magnetic Field
Force due to the self-gravity of the disc in the vertical direction is
considered to study its possible effects on the structure of a magnetized
advection-dominated accretion disc. We present steady-sate self similar
solutions for the dynamical structure of such a type of the accretion flows.
Our solutions imply reduced thickness of the disc because of the self-gravity.
It also imply that the thickness of the disc will increase by adding the
magnetic field strength.Comment: Accepted for publication in Astrophysics and Space Science
Extension of holomorphic functions and cohomology classes from non reduced analytic subvarieties
The goal of this survey is to describe some recent results concerning the L 2
extension of holomorphic sections or cohomology classes with values in vector
bundles satisfying weak semi-positivity properties. The results presented here
are generalized versions of the Ohsawa-Takegoshi extension theorem, and borrow
many techniques from the long series of papers by T. Ohsawa. The recent
achievement that we want to point out is that the surjectivity property holds
true for restriction morphisms to non necessarily reduced subvarieties,
provided these are defined as zero varieties of multiplier ideal sheaves. The
new idea involved to approach the existence problem is to make use of L 2
approximation in the Bochner-Kodaira technique. The extension results hold
under curvature conditions that look pretty optimal. However, a major unsolved
problem is to obtain natural (and hopefully best possible) L 2 estimates for
the extension in the case of non reduced subvarieties -- the case when Y has
singularities or several irreducible components is also a substantial issue.Comment: arXiv admin note: text overlap with arXiv:1703.00292,
arXiv:1510.0523
Acceptability of the Distress Thermometer and Problem List to community-based telephone cancer helpline operators, and to cancer patients and carers
Background Cancer can be a distressing experience for cancer patients and carers, impacting on psychological, social, physical and spiritual functioning. However, health professionals often fail to detect distress in their patients due to time constraints and a lack of experience. Also, with the focus on the patient, carer needs are often overlooked. This study investigated the acceptability of brief distress screening with the Distress Thermometer (DT) and Problem List (PL) to operators of a community-based telephone helpline, as well as to cancer patients and carers calling the service. Methods Operators (n = 18) monitored usage of the DT and PL with callers (cancer patients/carers, >18 years, and English-speaking) from September-December 2006 (n = 666). The DT is a single item, 11-point scale to rate level of distress. The associated PL identifies the cause of distress. Results The DT and PL were used on 90% of eligible callers, most providing valid responses. Benefits included having an objective, structured and consistent means for distress screening and triage to supportive care services. Reported challenges included apparent inappropriateness of the tools due to the nature of the call or level of caller distress, the DT numeric scale, and the level of operator training. Conclusions We observed positive outcomes to using the DT and PL, although operators reported some challenges. Overcoming these challenges may improve distress screening particularly by less experienced clinicians, and further development of the PL items and DT scale may assist with administration. The DT and PL allow clinicians to direct/prioritise interventions or referrals, although ongoing training and support is critical in distress screening
Feasibility of brief psychological distress screening by a community-based telephone helpline for cancer patients and carers
Background Up to one-third of people affected by cancer experience ongoing psychological distress and would benefit from screening followed by an appropriate level of psychological intervention. This rarely occurs in routine clinical practice due to barriers such as lack of time and experience. This study investigated the feasibility of community-based telephone helpline operators screening callers affected by cancer for their level of distress using a brief screening tool (Distress Thermometer), and triaging to the appropriate level of care using a tiered model. Methods Consecutive cancer patients and carers who contacted the helpline from September-December 2006 (n = 341) were invited to participate. Routine screening and triage was conducted by helpline operators at this time. Additional socio-demographic and psychosocial adjustment data were collected by telephone interview by research staff following the initial call. Results The Distress Thermometer had good overall accuracy in detecting general psychosocial morbidity (Hospital Anxiety and Depression Scale cut-off score ≥ 15) for cancer patients (AUC = 0.73) and carers (AUC = 0.70). We found 73% of participants met the Distress Thermometer cut-off for distress caseness according to the Hospital Anxiety and Depression Scale (a score ≥ 4), and optimal sensitivity (83%, 77%) and specificity (51%, 48%) were obtained with cut-offs of ≥ 4 and ≥ 6 in the patient and carer groups respectively. Distress was significantly associated with the Hospital Anxiety and Depression Scale scores (total, as well as anxiety and depression subscales) and level of care in cancer patients, as well as with the Hospital Anxiety and Depression Scale anxiety subscale for carers. There was a trend for more highly distressed callers to be triaged to more intensive care, with patients with distress scores ≥ 4 more likely to receive extended or specialist care. Conclusions Our data suggest that it was feasible for community-based cancer helpline operators to screen callers for distress using a brief screening tool, the Distress Thermometer, and to triage callers to an appropriate level of care using a tiered model. The Distress Thermometer is a rapid and non-invasive alternative to longer psychometric instruments, and may provide part of the solution in ensuring distressed patients and carers affected by cancer are identified and supported appropriately
Postural instability in an immersive Virtual Reality adapts with repetition and includes directional and gender specific effects
The ability to handle sensory conflicts and use the most appropriate sensory information is vital for successful recovery of human postural control after injury. The objective was to determine if virtual reality (VR) could provide a vehicle for sensory training, and determine the temporal and spatial nature of such adaptive changes. Twenty healthy subjects participated in the study (10 females). The subjects watched a 90-second VR simulation of railroad (rollercoaster) motion in mountainous terrain during five repeated simulations, while standing on a force platform that recorded their stability. The immediate response to watching the VR movie was an increased level of postural instability. Repeatedly watching the same VR movie significantly reduced both the anteroposterior (62%, p < 0.001) and lateral (47%, p = 0.001) energy used. However, females adapted more slowly to the VR stimuli as reflected by higher use of total (p = 0.007), low frequency (p = 0.027) and high frequency (p = 0.026) energy. Healthy subjects can significantly adapt to a multidirectional, provocative, visual environment after 4–5 repeated sessions of VR. Consequently, VR technology might be an effective tool for rehabilitation involving visual desensitisation. However, some females may require more training sessions to achieve effects with VR
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