176 research outputs found
GPU-based 3D iceball modeling for fast cryoablation simulation and planning
Purpose The elimination of abdominal tumors by percutaneous cryoablation has been shown to be an effective and less invasive alternative to open surgery. Cryoablation destroys malignant cells by freezing them with one or more cryoprobes inserted into the tumor through the skin. Alternating cycles of freezing and thawing produce an enveloping iceball that causes the tumor necrosis. Planning such a procedure is difficult and time-consuming, as it is necessary to plan the number and cryoprobe locations and predict the iceball shape which is also influenced by the presence of heating sources, e.g., major blood vessels and warm saline solution, injected to protect surrounding structures from the cold. Methods This paper describes a method for fast GPU-based iceball modeling based on the simulation of thermal propagation in the tissue. Our algorithm solves the heat equation within a cube around the cryoprobes tips and accounts for the presence of heating sources around the iceball. Results Experimental results of two studies have been obtained: an ex vivo warm gel setup and simulation on five retrospective patient cases of kidney tumors cryoablation with various levels of complexity of the vascular structure and warm saline solution around the tumor tissue. The experiments have been conducted in various conditions of cube size and algorithm implementations. Results show that it is possible to obtain an accurate result within seconds. Conclusion The promising results indicate that our method yields accurate iceball shape predictions in a short time and is suitable for surgical planning
Effect of different physio-chemical factors on sex expression and fruit yield in green-house cucumber
Male flower expression is considered an important aim in greenhouse cucumber breeding for creating paternal lines as a base for hybrid progeny. The study was carried out to evaluate the effects of different treatments on sex expression and fruit yield of cucumber in two different season (autumn-winter and spring-summer), in particular this research focuses on the influence of 1) usage of two chemical agents: silver thiosulphate [Ag(S2O3)2-3] and silver nitrate (AgNO3) at different concentration, respectively 200 and 500 ppm and 100, 200 and 300 ppm 2) plant development stages at the moment of the treatment (5, 10, and 15-leaf growth stages) and 3) application of single or double sprayings. Analysis of variance showed that season, chemical applications and number of spaying had significant effect on the induction of a higher number of male flowers. A positive significant effect of season suggested that longer days and higher temperature promote the formation of male flowers in cucumber. This study showed that male flower production was induced by all concentrations of silver ions, especially high concentrations. Important traits related to change of sex expression such as the number of days to male flowering and the number of male flowers are more affected by different interactions of studied factors in contrast to vegetative and yield related traits. Also, the quadruple interaction effects indicated that silver ion could change sex expression at higher temperatures and longer days (second season in summer) with high concentration when applied in 15 leaf stage for AgNO3 and 5 and 15 leaf growth stage for Ag(S2O3)2-3 with double spraying. Consequently, female lines can be induced to male flowering with silver ions, thus increasing the feasibility of large scale seed production of gynoecious × gynoecious cucumber hybrid
Value-Driven Analysis of New Paradigms in Space Architectures: An Ilities-Based Approach
Current commercial, civil, and military space architecture designs perform exquisitely and reliably. However, today’s architecture paradigms are also characterized by expensive launches, large and expensive high-performance spacecraft, long development cycles, and wide variations in ground architectures. While current assets provide high-quality services, and future assets are slated to improve performance within the same design frameworks, proposed future architectures may not be capitalizing on technology improvements, system innovations, or policy alternatives explored during the last two decades. This paper identifies five “trends” along which space architectures may develop, aimed at granting systems several “ilities,” such as resiliency, robustness, flexibility, scalability, and affordability. The trends examined include: commercialization of space, significant reductions in launch costs and the development of hybrid or reusable launch systems, development of on-orbit infrastructure and servicing, aggregation or disaggregation of orbital assets, and the automation and standardization of ground architectures. Further refinement of these key technological and system trends could result in major paradigm shifts in the development and fielding of space operations as well as lead to space architecture designs in the future that are radically different from those today. Within the framework of systems engineering ilities and risk management, this paper reviews current literature surrounding these new change trends and justifies their potential to cause significant paradigm shifts. By examining the work and research conducted so far through an ilities-based approach, systems engineers can more fully appreciate the value being offered by these trends
Chiral drag force
We provide a holographic evaluation of novel contributions to the drag force
acting on a heavy quark moving through strongly interacting plasma. The new
contributions are chiral in that they act in opposite directions in plasmas
containing an excess of left- or right-handed quarks and in that they are
proportional to the coefficient of the axial anomaly. These new contributions
to the drag force act either parallel to or antiparallel to an external
magnetic field or to the vorticity of the fluid plasma. In all these respects,
these contributions to the drag force felt by a heavy quark are analogous to
the chiral magnetic effect on light quarks. However, the new contribution to
the drag force is independent of the electric charge of the heavy quark and is
the same for heavy quarks and antiquarks. We show that although the chiral drag
force can be non-vanishing for heavy quarks that are at rest in the local fluid
rest frame, it does vanish for heavy quarks that are at rest in a suitably
chosen frame. In this frame, the heavy quark at rest sees counterpropagating
momentum and charge currents, both proportional to the axial anomaly
coefficient, but feels no drag force. This provides strong concrete evidence
for the absence of dissipation in chiral transport, something that has been
predicted previously via consideration of symmetries. Along the way to our
principal results, we provide a general calculation of the corrections to the
drag force due to the presence of gradients in the flowing fluid in the
presence of a nonzero chemical potential. We close with a consequence of our
result that is at least in principle observable in heavy ion collisions, namely
an anticorrelation between the direction of the CME current for light quarks in
a given event and the direction of the kick given to the momentum of all the
heavy quarks and antiquarks in that event.Comment: 28 pages, small improvement to the discussion of gravitational
anomaly, references adde
Retropubic, laparoscopic and mini-laparoscopic radical prostatectomy : a prospective assessment of patient scar satisfaction
Published online: 26 October 2014PURPOSE:
To compare patient scar satisfaction after retropubic, standard laparoscopic, mini-laparoscopic (ML) and open radical prostatectomy (RP).
METHODS:
Patients undergoing RP for a diagnosis of localized prostate cancer at a single academic hospital between September 2012 and December 2013 were enrolled in this prospective nonrandomized study. The patients were included in three study arms: open surgery, VLP and ML. A skin stapler was used for surgical wound closure in all cases. Demographic and main surgical outcomes, including perioperative complications, were analyzed. Surgical scar satisfaction was measured using the Patient and Observer Scar Assessment Questionnaire (POSAS) and the two Body Image Questionnaire (BIQ) scales, respectively, recorded at skin clips removal and either at 6 months after surgery.
RESULTS:
Overall, 32 patients were enrolled and completed the 6 month of follow-up. At clips removal, laparoscopic approaches offered better scar result than open surgery according to the POSAS. However, at 6 months, no differences were detected between VLP and open, whereas ML was still associated with a better scar outcome (p = 0.001). This finding was also confirmed by both BIQ scales, including the body image score (ML 9.8 ± 1.69, open 15.73 ± 3.47, VLP 13.27 ± 3.64; p = 0.001) and the cosmetic score (ML 16.6 ± 4.12, open 10 ± 1.9, LP 12.91 ± 3.59; p = 0.001). Small sample size and lack of randomization represent the main limitations of this study.
CONCLUSIONS:
ML RP offers a better cosmetic outcome when compared to both open and standard laparoscopic RP, representing a step toward minimal surgical scar. The impact of scar outcome on RP patients' quality of life remains to be determined
Vaccines against toxoplasma gondii : challenges and opportunities
Development of vaccines against Toxoplasma gondii infection in humans is of high priority, given the high burden of disease in some areas of the world like South America, and the lack of effective drugs with few adverse effects. Rodent models have been used in research on vaccines against T. gondii over the past decades. However, regardless of the vaccine construct, the vaccines have not been able to induce protective immunity when the organism is challenged with T. gondii, either directly or via a vector. Only a few live, attenuated T. gondii strains used for immunization have been able to confer protective immunity, which is measured by a lack of tissue cysts after challenge. Furthermore, challenge with low virulence strains, especially strains with genotype II, will probably be insufficient to provide protection against the more virulent T. gondii strains, such as those with genotypes I or II, or those genotypes from South America not belonging to genotype I, II or III. Future studies should use animal models besides rodents, and challenges should be performed with at least one genotype II T. gondii and one of the more virulent genotypes. Endpoints like maternal-foetal transmission and prevention of eye disease are important in addition to the traditional endpoint of survival or reduction in numbers of brain cysts after challenge
Verbal instructions override the meaning of facial expressions
Psychological research has long acknowledged that facial expressions can implicitly trigger affective
psychophysiological responses. However, whether verbal information can alter the meaning of facial
emotions and corresponding response patterns has not been tested. This study examined emotional
facial expressions as cues for instructed threat-of-shock or safety, with a focus on defensive responding.
In addition, reversal instructions were introduced to test the impact of explicit safety instructions on
fear extinction. Forty participants were instructed that they would receive unpleasant electric shocks,
for instance, when viewing happy but not angry faces. In a second block, instructions were reversed
(e.g., now angry faces cued shock). Happy, neutral, and angry faces were repeatedly presented, and
auditory startle probes were delivered in half of the trials. The defensive startle reflex was potentiated
for threat compared to safety cues. Importantly, this effect occurred regardless of whether threat
was cued by happy or angry expressions. Although the typical pattern of response habituation was
observed, defense activation to newly instructed threat cues remained significantly enhanced in the
second part of the experiment, and it was more pronounced in more socially anxious participants.
Thus, anxious individuals did not exhibit more pronounced defense activation compared to less anxious
participants, but their defense activation was more persistent
Experimental signatures of the mixed axial-gravitational anomaly in the Weyl semimetal NbP
Weyl semimetals are materials where electrons behave effectively as a kind of
massless relativistic particles known asWeyl fermions. These particles occur in
two flavours, or chiralities, and are subject to quantum anomalies, the
breaking of a conservation law by quantum fluctuations. For instance, the
number of Weyl fermions of each chirality is not independently conserved in
parallel electric and magnetic field, a phenomenon known as the chiral anomaly.
In addition, an underlying curved spacetime provides a distinct contribution to
a chiral imbalance, an effect known as the mixed axial-gravitational anomaly,
which remains experimentally elusive. However, the presence of a mixed
gauge-gravitational anomaly has recently been tied to thermoelectrical
transport in a magnetic field, even in flat spacetime, opening the door to
experimentally probe such type of anomalies in Weyl semimetals. Using a
temperature gradient, we experimentally observe a positive longitudinal
magnetothermoelectric conductance (PMTC) in the Weyl semimetal NbP for
collinear temperature gradients and magnetic fields (DT || B) that vanishes in
the ultra quantum limit. This observation is consistent with the presence of a
mixed axial-gravitational anomaly. Our work provides clear experimental
evidence for the existence of a mixed axial-gravitational anomaly of Weyl
fermions, an outstanding theoretical concept that has so far eluded
experimental detection
Blogging the Virtual: New Geographies of Domination and Resistance In and Beyond Russia
Russia’s accelerating authoritarian turn has not ignored the internet, and in recent years, the Russian state has clamped down on internet activities that diverge from the statist line, employing a variety of strategies to dominate online spaces. Nevertheless, oppositional voices flourish on the Russian internet, taking shape in independent blogs and videos. This paper explores three political bloggers through surveillant and resistance assemblages, making sense of this contestation through an interpretation of the Deleuzian virtual that underscores the emancipatory potential of online activities for producing more egalitarian configurations, but also taking stock of the ways that these technologies have increased domination. Encompassing the blurriness between digital and corporeal spaces, the paper contributes by revealing new geographies of contestation against state strategies to dominate the Russian internet. Overlapping with but not corresponding to Russian territorial boundaries, these dynamics highlight shifting spaces of power and resistance in the increasingly illiberal world
- …