1,566 research outputs found
On the perturbative S-matrix of generalized sine-Gordon models
Motivated by its relation to the Pohlmeyer reduction of AdS_5 x S^5
superstring theory we continue the investigation of the generalized sine-Gordon
model defined by SO(N+1)/SO(N) gauged WZW theory with an integrable potential.
Extending our previous work (arXiv:0912.2958) we compute the one-loop
two-particle S-matrix for the elementary massive excitations. In the N = 2 case
corresponding to the complex sine-Gordon theory it agrees with the charge-one
sector of the quantum soliton S-matrix proposed in hep-th/9410140. In the case
of N > 2 when the gauge group SO(N) is non-abelian we find a curious anomaly in
the Yang-Baxter equation which we interpret as a gauge artifact related to the
fact that the scattered particles are not singlets under the residual global
subgroup of the gauge group
Intrastromal corneal ring segments: how successful is the surgical treatment of keratoconus?
This review evaluates the outcomes of intrastromal corneal ring segment (ICRS) implantation for the treatment of keratoconus considering a new grading system based on the preoperative visual impairment of the patient. Additionally, a five-year follow-up analysis of patients with stable and progressive keratoconus is performed in order to assess the long term stability of the surgical procedure. Corrected distance visual acuity decreased statistically significantly in patients with mild keratoconus (P < 0.01) but statistically significantly increased in all other grades (P < 0.05). The improvement in visual acuity and the decrease of keratometric and aberrometric values were stable throughout a long period of time in patients with stable keratoconus. In patients with progressive form keratoconus, a significant improvement was found immediately after the procedure, however clinically relevant regression greater than 3 D was observed at the end of the follow up period
Performance of yam microtubers from temporary immersion system in field conditions
The yam clones ÂŽPacala DuclosÂŽ and ÂŽBelepÂŽ of Dioscorea alata were used to evaluate the performance of microtubers formed in temporary immersion systems (TIS) in field conditions. Previously sprouted microtubers with a fresh weight higher than 3.0 gFW were used while in vitro plants and tuber crowns from conventional propagation methods served as control. In both clones there were no significant differences in qualitative morphological characters between plants from microtubers and in vitro plants for all traits but both differed significantly from plants obtained from tuber crowns. The same trend was observed for number, length, diameter and fresh weight of tubers produced 36 weeks after field planting. The number of tubers formed per plant raised from microtubers doubled that raised from tuber crowns in both clones. Microtubers from temporary immersion systems can be grown on the field and used in original seed production programs.Key words: Microtuber, yam, field, temporary immersion system
Using time-use diaries to track changing behavior across successive stages of COVID-19 social restrictions
How did people change their behavior over the different phases of the UK COVID-19 restrictions, and how did these changes affect their risk of being exposed to infection? Time-use diary surveys are unique in providing a complete chronicle of daily behavior: 24-h continuous records of the populationsâ activities, their social context, and their location. We present results from four such surveys, collected in real time from representative UK samples, both before and at three points over the course of the current pandemic. Comparing across the four waves, we find evidence of substantial changes in the UK populationâs behavior relating to activities, locations, and social context. We assign different levels of risk to combinations of activities, locations, and copresence to compare risk-related behavior across successive âlockdowns.â We find evidence that during the second lockdown (November 2020), there was an increase in high-risk behaviors relative to the first (starting March 2020). This increase is shown to be associated with more paid work time in the workplace. At a time when capacity is still limited both in respect of immunization and trackâtrace technology, governments must continue to rely on changes in peopleâs daily behaviors to contain the spread of COVID-19 and similar viruses. Time-use diary information of this type, collected in real time across the course of the COVID-19 pandemic, can provide policy makers with information to assess and quantify changes in daily behaviors and the impact they are likely to have on overall behavioral-associated risks
Meta-analysis shows no consistent evidence for senescence in ejaculate traits across animals
Male reproductive traits such as ejaculate size and quality, are expected to decline with advancing age due to senescence. It is however unclear whether this expectation is upheld across taxa. We perform a meta-analysis on 379 studies, to quantify the effects of advancing male age on ejaculate traits across 157 species of non-human animals. Contrary to predictions, we find no consistent pattern of age-dependent changes in ejaculate traits. This result partly reflects methodological limitations, such as studies sampling a low proportion of adult lifespan, or the inability of meta-analytical approaches to document non-linear ageing trajectories of ejaculate traits; which could potentially lead to an underestimation of senescence. Yet, we find taxon-specific differences in patterns of ejaculate senescence. For instance, older males produce less motile and slower sperm in ray-finned fishes, but larger ejaculates in insects, compared to younger males. Notably, lab rodents show senescence in most ejaculate traits measured. Our study challenges the notion of universal reproductive senescence, highlighting the need for controlled methodologies and a more nuanced understanding of reproductive senescence, cognisant of taxon-specific biology, experimental design, selection pressures, and life-history
Outcome analysis of intracorneal ring segments for the treatment of keratoconus based on visual, refractive, and aberrometric impairment
PURPOSE:
To analyze the outcomes of intracorneal ring segment (ICRS) implantation for the treatment of keratoconus based on preoperative visual impairment.
DESIGN:
Multicenter, retrospective, nonrandomized study.
METHODS:
A total of 611 eyes of 361 keratoconic patients were evaluated. Subjects were classified according to their preoperative corrected distance visual acuity (CDVA) into 5 different groups: grade I, CDVA of 0.90 or better; grade II, CDVA equal to or better than 0.60 and worse than 0.90; grade III, CDVA equal to or better than 0.40 and worse than 0.60; grade IV, CDVA equal to or better than 0.20 and worse than 0.40; and grade plus, CDVA worse than 0.20. Success and failure indices were defined based on visual, refractive, corneal topographic, and aberrometric data and evaluated in each group 6 months after ICRS implantation.
RESULTS:
Significant improvement after the procedure was observed regarding uncorrected distance visual acuity in all grades (P < .05). CDVA significantly decreased in grade I (P < .01) but significantly increased in all other grades (P < .05). A total of 37.9% of patients with preoperative CDVA 0.6 or better gained 1 or more lines of CDVA, whereas 82.8% of patients with preoperative CDVA 0.4 or worse gained 1 or more lines of CDVA (P < .01). Spherical equivalent and keratometry readings showed a significant reduction in all grades (P †.02). Corneal higher-order aberrations did not change after the procedure (P ℠.05).
CONCLUSIONS:
Based on preoperative visual impairment, ICRS implantation provides significantly better results in patients with a severe form of the disease. A notable loss of CDVA lines can be expected in patients with a milder form of keratoconus
Alleviating the non-ultralocality of coset sigma models through a generalized Faddeev-Reshetikhin procedure
The Faddeev-Reshetikhin procedure corresponds to a removal of the
non-ultralocality of the classical SU(2) principal chiral model. It is realized
by defining another field theory, which has the same Lax pair and equations of
motion but a different Poisson structure and Hamiltonian. Following earlier
work of M. Semenov-Tian-Shansky and A. Sevostyanov, we show how it is possible
to alleviate in a similar way the non-ultralocality of symmetric space sigma
models. The equivalence of the equations of motion holds only at the level of
the Pohlmeyer reduction of these models, which corresponds to symmetric space
sine-Gordon models. This work therefore shows indirectly that symmetric space
sine-Gordon models, defined by a gauged Wess-Zumino-Witten action with an
integrable potential, have a mild non-ultralocality. The first step needed to
construct an integrable discretization of these models is performed by
determining the discrete analogue of the Poisson algebra of their Lax matrices.Comment: 31 pages; v2: minor change
Simplified R-Symmetry Breaking and Low-Scale Gauge Mediation
We argue that some of the difficulties in constructing realistic models of
low-scale gauge mediation are artifacts of the narrow set of models that have
been studied. In particular, much attention has been payed to the scenario in
which the Goldstino superfield in an O'Raifeartaigh model is responsible for
both supersymmetry breaking and R-symmetry breaking. In such models, the
competing problems of generating sufficiently massive gauginos while preserving
an acceptably light gravitino can be quite challenging. We show that by sharing
the burdens of breaking supersymmetry and R-symmetry with a second field, these
problems are easily solved even within the O'Raifeartaigh framework. We present
explicit models realizing minimal gauge mediation with a gravitino mass in the
eV range that are both calculable and falsifiable.Comment: 31 pages, 4 figures, references added, minor change
Invarianza factorial del Cuestionario de Autoconcepto FĂsico Modificado (CAF-M) en universitarios mexicanos deportistas y no deportistas
El objetivo principal del presente estudio fue examinar la invarianza factorial del Cuestionario de Autoconcepto FĂsico Modicado (CAF- M) en universitarios mexicanos deportistas y no deportistas. La muestra total fue de 1.528 universitarios mexicanos, 651 deportistas y 877 no deportistas, con una edad media de 20,78 años (DE = 2,45). Los anĂĄlisis factoriales conrmatorios mostraron que una estructura de dos factores es viable y adecuada para ambas poblaciones. Atendiendo a criterios estadĂsticos y sustantivos, la estructura de dos factores (competencia motora y atractivo fĂsico) ha mostrado adecuados indicadores de ajuste de abilidad y validez. AdemĂĄs, la estructura factorial, las cargas factoriales y los interceptos se consideran invariantes en las dos poblaciones estudiadas. Se encontraron diferencias entre los universitarios deportistas y no deportistas para las medias de ambos factores. Por Ășltimo, el presente estudio tambiĂ©n conrma la validez del modelo bidimensional del autoconcepto fĂsico. Futuras investigaciones deberĂan replicar estos hallazgos en poblaciones con diferentes factores culturales y personales.
General Gauge Mediation at the Weak Scale
We completely characterize General Gauge Mediation (GGM) at the weak scale by
solving all IR constraints over the full parameter space. This is made possible
through a combination of numerical and analytical methods, based on a set of
algebraic relations among the IR soft masses derived from the GGM boundary
conditions in the UV. We show how tensions between just a few constraints
determine the boundaries of the parameter space: electroweak symmetry breaking
(EWSB), the Higgs mass, slepton tachyons, and left-handed stop/sbottom
tachyons. While these constraints allow the left-handed squarks to be
arbitrarily light, they place strong lower bounds on all of the right-handed
squarks. Meanwhile, light EW superpartners are generic throughout much of the
parameter space. This is especially the case at lower messenger scales, where a
positive threshold correction to coming from light Higgsinos and winos is
essential in order to satisfy the Higgs mass constraint.Comment: 43 pages, 20 figures, mathematica package included in the sourc
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