Three-dimensional Heisenberg model with Dzyaloshinskii-Moriya interaction: A Monte Carlo study.

The three-dimensional classical Heisenberg model on a simple cubic lattice with Dzyaloshinskii-Moriya (DM) interactions between nearest-neighbors in all directions has been studied using Monte Carlo simulations. The Metropolis algorithm, combined with single histogram reweighting techniques and finite-size scaling analyses, has been used to obtain the thermodynamic behavior of the system in the thermodynamic limit. Simulations were performed with the same set of interaction parameters for both shifted boundary conditions (SBC) and fluctuating boundary conditions (FBC). Because of an incommensurability caused by the DM interaction, the SBC incorporated a fixed shift angle at the boundary which varies as a function of the DM interaction and lattice size. This SBC method decreases the simulation time significantly, but the distribution of states is somewhat different than that obtained with FBC. The ground state for nonzero DM interaction is a spiral configuration where the spins are restricted to lie in planes perpendicular to the DM vector. We found that this spiral configuration undergoes a conventional second-order phase transition into a disordered, paramagnetic state with the transition temperature being a function of the magnitude of the DM interaction. The limiting case with only DM interaction in the model has also been considered. The critical exponent ν, the critical exponent ratios α/ν, ß/ν, γ/ν, as well as the critical temperature T_{c} and fourth-order cumulant of the order parameter U_{4}^{*} at T_{c} have been estimated for different magnitudes of DM interaction. The critical exponents and cumulants at the transition are different from those for the three-dimensional Heisenberg model, but the ratios α/ν, ß/ν, γ/ν, U_{4}^{*}/ν are the same, implying that weak universality is valid for all values of DM interaction. Structure factor calculations for particular cases have been performed considering SBC and FBC in the simulations with different lattice sizes at the critical temperatures.

Incommensurate phases in the two-dimensional XY model with Dzyaloshinskii-Moriya interactions.

The two-dimensional XY model with Dzyaloshinskii-Moriya interaction has been studied through extensive Monte Carlo simulations. A hybrid algorithm consisting of single-spin Metropolis and Swendsen-Wang cluster-spin updates has been employed. Single histogram techniques have been used to obtain the thermodynamic variables of interest and finite-size-scaling analysis has led to the phase transition behavior in the thermodynamic limit. Fluctuating boundary conditions have been utilized in order to match the incommensurability between the spin structures and the finite lattice sizes due to the Dzyaloshinskii-Moriya interaction. The effects of the fluctuating boundary conditions have been analyzed in detail in both commensurate and incommensurate cases. The Berezinskii-Kosterlitz-Thouless transition temperature has been obtained as a function of the Dzyaloshinskii-Moriya interaction and the results are in excellent agreement with the exact equation for the transition line. The spin-spin correlation function critical exponent has been computed as a function of the Dzyaloshinskii-Moriya interaction and temperature. In the incommensurate cases, optimal sizes for the finite lattices and the distribution of the boundary shift angle have been extracted. Analysis of the low temperature configurations and the corresponding vortex-antivortex pairs have also been addressed in some regions of the phase diagram.

A multichannel feature-based approach for longitudinal lung CT registration in the presence of radiation induced lung damage.

Quantifying parenchymal tissue changes in the lungs is imperative in furthering the study of radiation induced lung damage (RILD). Registering lung images from different time-points is a key step of this process. Traditional intensity-based registration approaches fail this task due to the considerable anatomical changes that occur between timepoints. This work proposes a novel method to successfully register longitudinal pre- and post-radiotherapy (RT) lung computed tomography (CT) scans that exhibit large changes due to RILD, by extracting consistent anatomical features from CT (lung boundaries, main airways, vessels) and using these features to optimise the registrations. Pre-RT and 12 month post-RT CT pairs from fifteen lung cancer patients were used for this study, all with varying degrees of RILD, ranging from mild parenchymal change to extensive consolidation and collapse. For each CT, signed distance transforms from segmentations of the lungs and main airways were generated, and the Frangi vesselness map was calculated. These were concatenated into multi-channel images and diffeomorphic multichannel registration was performed for each image pair using NiftyReg. Traditional intensity-based registrations were also performed for comparison purposes. For the evaluation, the pre- and post-registration landmark distance was calculated for all patients, using an average of 44 manually identified landmark pairs per patient. The mean (standard deviation) distance for all datasets decreased from 15.95 (8.09) mm pre-registration to 4.56 (5.70) mm post-registration, compared to 7.90 (8.97) mm for the intensity-based registrations. Qualitative improvements in image alignment were observed for all patient datasets. For four representative subjects, registrations were performed for three additional follow-up timepoints up to 48 months post-RT and similar accuracy was achieved. We have demonstrated that our novel multichannel registration method can successfully align longitudinal scans from RILD patients in the presence of large anatomical changes such as consolidation and atelectasis, outperforming the traditional registration approach both quantitatively and through thorough visual inspection.

In Silico Ventilation Within the Dose-Volume is Predictive of Lung Function Post-radiation Therapy in Patients with Lung Cancer.

Lung cancer is a leading cause of death worldwide. Radiation therapy (RT) is one method to treat this disease. A common side effect of RT for lung cancer is radiation-induced lung damage (RILD) which leads to loss of lung function. RILD often compounds pre-existing smoking-related regional lung function impairment. It is difficult to predict patient outcomes due to large variability in individual response to RT. In this study, the capability of image-based modelling of regional ventilation in lung cancer patients to predict lung function post-RT was investigated. Twenty-five patient-based models were created using CT images to define the airway geometry, size and location of tumour, and distribution of emphysema. Simulated ventilation within the 20 Gy isodose volume showed a statistically significant negative correlation with the change in forced expiratory volume in 1 s 12-months post-RT (p = 0.001, R = - 0.61). Patients with higher simulated ventilation within the 20 Gy isodose volume had a greater loss in lung function post-RT and vice versa. This relationship was only evident with the combined impact of tumour and emphysema, with the location of the emphysema relative to the dose-volume being important. Our results suggest that model-based ventilation measures can be used in the prediction of patient lung function post-RT.

Troglostrongylus brevior is the dominant lungworm infecting feral cats in Jerusalem.

Feline lungworms infect the respiratory tract of wild and domestic cats, causing infection often associated with clinical disease. Until recently, Aelurostrongylus abstrusus has been considered the most relevant species of lungworm, while Troglostrongylus brevior was considered of less significance. Fecal samples of feral cats from Jerusalem, Israel, collected over a year, were examined for first stage lungworm larvae (L1) using the Baermann method. Positive samples were morphologically identified, and their species identity was molecularly confirmed. Forty of 400 (10.0%) cats were lungworm-positive, of which 38/40 (95.0%) shed Troglostrongylus brevior and 6/40 (15.0%) shed Aelurostrongylus abstrusus. Four cats (10.0%) had mixed infections with both lungworm species. L1 shedding was associated with clinical respiratory signs in 11 (19.0%) T. brevior shedding cats of a total of 58 cats manifesting respiratory signs, while 23/342 (6.7%) cats without respiratory signs were L1-positive (p = 0.006). Non-respiratory clinical signs were also found to be more prevalent in L1 shedders (p = 0.012). A young kitten ≤ 4 weeks of age shed T. brevior L1 larvae. DNA sequences of both lungworm species using the ribosomal internal transcribed spacer 2 (ITS2) locus were > 99% similar to other sequences deposited in GenBank, suggesting that T. brevior and A. abstrusus ITS2 sequences are both highly conserved. In conclusion, L1 shedding in feral cats from Jerusalem were mostly caused by T. brevior with only a small proportion involving A. abstrusus, different from many studies from other geographical regions.

First report of Onchocerca lupi from Israel and confirmation of two genotypes circulating among canine, feline and human hosts.

Onchocerca lupi is a parasitic filarioid and the causative agent of canine ocular onchocercosis, a zoonotic disease of domestic dogs with sporadic reports in humans. A 13-year-old dog with no travel history outside of Israel was presented to an ophthalmology veterinary clinic in Israel with severe right ocular and periocular disease. After surgical exploration, thin helminths were removed from the dorsal sclera of the eye and identified as Onchocerca lupi by polymerase chain reaction according to the cytochrome c oxidase subunit I (cox1), reduced nicotinamide adenine dinucleotide dehydrogenase subunit 5 (nad5) and 12S rRNA genes. Phylogenetic trees and haplotype networks of the cox1 and nad5 genes confirmed the circulation of two genotypes: genotype 1 with worms from dogs, cats and humans from both the Old and New Worlds, and genotype 2 with specimens from Portugal and Spain. The Israeli sequences clustered in genotype 1 and were identical to O. lupi from the USA. Evidence of two genotypes separated geographically sheds light on the phylogeography and evolution of this zoonotic pathogen, and suggests a diverse pathology observed in different regions of the world.

Prediction of a positive circumferential resection margin at surgery following neoadjuvant chemotherapy for adenocarcinoma of the oesophagus.

Background: A positive circumferential resection margin (CRM) has been associated with higher rates of locoregional recurrence and worse survival in oesophageal cancer. The aim of this study was to establish if clinicopathological and radiological variables might predict CRM positivity in patients who received neoadjuvant chemotherapy before surgery for oesophageal adenocarcinoma. Methods: Multivariable analysis of clinicopathological and CT imaging characteristics considered potentially predictive of CRM was performed at initial staging and following neoadjuvant chemotherapy. Prediction models were constructed. The area under the curve (AUC) with 95% confidence intervals (c.i.) from 1000 bootstrapping was assessed. Results: A total of 223 patients were included in the study. Poor differentiation (odds ratio (OR) 2·84, 95 per cent c.i. 1·39 to 6·01) and advanced clinical tumour status (T3-4) (OR 2·93, 1·03 to 9·48) were independently associated with an increased CRM risk at diagnosis. CT-assessed lack of response (stable or progressive disease) following chemotherapy independently corresponded with an increased risk of CRM positivity (OR 3·38, 1·43 to 8·50). Additional CT evidence of local invasion and higher CT tumour volume (14 cm3) improved the performance of a prediction model, including all the above parameters, with an AUC (c-index) of 0·76 (0·67 to 0·83). Variables associated with significantly higher rates of locoregional recurrence were pN status (P = 0·020), lymphovascular invasion (P = 0·007) and poor response to chemotherapy (Mandard score 4-5) (P = 0·006). CRM positivity was associated with a higher locoregional recurrence rate, but this was not statistically significant (P = 0·092). Conclusion: The presence of advanced cT status, poor tumour differentiation, and CT-assessed lack of response to chemotherapy, higher tumour volume and local invasion can be used to identify patients at risk of a positive CRM following neoadjuvant chemotherapy.

Antecedentes: Un margen de resección circunferencial (circumferential resection margin, CRM) positivo se ha asociado con tasas más elevadas de recidiva locorregional y peor supervivencia en el cáncer de esófago. El objetivo de este estudio fue establecer si las variables clínico­patológicas y radiológicas podrían predecir la positividad del CRM en el adenocarcinoma de esófago tras quimioterapia neoadyuvante antes de la cirugía. Métodos: Se realizó un análisis multivariable de las características clínico­patológicas y de la tomografía computarizada (computed tomography, CT) que se consideraron potencialmente predictivas de CRM en la estadificación inicial y tras la quimioterapia neoadyuvante. Se construyeron modelos de predicción. Se evaluó el área bajo la curva (area under curve, AUC) con el i.c. del 95% a partir de 1.000 muestras bootstrap. Resultados: Se incluyeron 223 pacientes en el estudio. Una pobre diferenciación (razón de oportunidades, odds ratio, OR 2,84, i.c. del 95% 1,39­6,01) y un estadio clínico T avanzado (T3­4) (OR 2,93, i.c. del 95% 1,03­9,48) se asociaron de forma independiente con un riesgo aumentado de CRM en el diagnóstico. La falta de respuesta en la CT (estable o enfermedad en progresión) tras la quimioterapia se correspondía de forma independiente con un riesgo aumentado de CRM positivo (OR 3,38, i.c. del 95% 1,43­8,50). Además, la evidencia por CT de invasión local y un mayor volumen del tumor en CT (14 cm3) mejoraron el funcionamiento del modelo predictivo, incluyendo todos los parámetros previamente señalados; con AUC (índice c) de 0,76 (0,68­0,83). Las variables asociadas de forma significativa con tasas más elevadas de recidiva locorregional fueron el estado de los ganglios linfáticos patológicos (P = 0,002), la invasión linfovascular (P = 0,007) y la respuesta pobre a la quimioterapia (Mandard 4 y 5 (P = 0,006)). La positividad del CRM se asoció con una tasa de recidiva locorregional más elevada pero sin alcanzar significación estadística (P = 0,09). Conclusión: La presencia de un estadio clínico T avanzado, tumor pobremente diferenciado, falta de respuesta a la quimioterapia en la TC, mayor volumen del tumor en la TC e invasión local pueden ser utilizados para identificar pacientes en riesgo de un CRM positivo tras quimioterapia neoadyuvante.

Probing predictions due to the nonlocal interface Hamiltonian: Monte Carlo simulations of interfacial fluctuations in Ising films.

Extensive Monte Carlo simulations have been performed on an Ising ferromagnet under conditions that would lead to complete wetting in a semi-infinite system. We studied an L×L×D slab geometry with oppositely directed surface fields so that a single interface is formed and can undergo a localization-delocalization transition. Under the chosen conditions the interface position is, on average, in the middle of the slab, and its fluctuations allow a sensitive test of predictions that the effective interactions between the interface and the confining surfaces are nonlocal. The decay of distance dependent correlation functions are measured within the surface, in the middle of the slab, and between middle and the surface for slabs of varying thickness D. From Fourier transforms of these correlation functions a nonlinear correlation length is extracted, and its behavior is found to confirm theoretical predictions for D>6 lattice spacings.

Finite-size scaling for a first-order transition where a continuous symmetry is broken: The spin-flop transition in the three-dimensional XXZ Heisenberg antiferromagnet.

Finite-size scaling for a first-order phase transition where a continuous symmetry is broken is developed using an approximation of Gaussian probability distributions with a phenomenological "degeneracy" factor included. Predictions are compared with data from Monte Carlo simulations of the three-dimensional, XXZ Heisenberg antiferromagnet in a field in order to study the finite-size behavior on a L×L×L simple cubic lattice for the first-order "spin-flop" transition between the Ising-like antiferromagnetic state and the canted, XY-like state. Our theory predicts that for large linear dimension L the field dependence of all moments of the order parameters as well as the fourth-order cumulants exhibit universal intersections. Corrections to leading order should scale as the inverse volume. The values of these intersections at the spin-flop transition point can be expressed in terms of a factor q that characterizes the relative degeneracy of the ordered phases. Our theory yields q=π, and we present numerical evidence that is compatible with this prediction. The agreement between the theory and simulation implies a heretofore unknown universality can be invoked for first-order phase transitions.

Urinary incontinence associated with Mesocestoides vogae infection in a dog.

Peritoneal larval cestodiasis caused by Mesocestoides spp. is a rare infection in dogs. A 6-year-old female dog was presented for veterinary care with urinary incontinence which started 1 year earlier. After performing hematology, ultrasound, and computerized tomography, an exploratory laparotomy revealed canine peritoneal larval cestodiasis (CPLC) with the presence of Mesocestoides vogae (syn. Mesocestoides corti) tetrathyridia confirmed by morphological identification and PCR and DNA sequencing. Parasitic cysts were found around the urinary bladder and appeared to inhibit its normal function. An initial treatment with 5 mg/kg praziquantel subcutaneously every 2 weeks for four treatments failed to alleviate the clinical signs, and only treatment with fenbendazole at 100 mg/kg P.O. twice daily for 28 days was associated with the disappearance of ascites and regaining of urinary control. This is the first report of CPLC associated with urinary incontinence in dogs and the first description of this cyclophyllidean cestode in dogs in Israel.

The association between birth weight at term and long-term endocrine morbidity of the offspring.

OBJECTIVE: To investigate whether small-for-gestational-age (SGA) and large-for-gestational-age (LGA) birth weight at-term poses an increased risk for long-term pediatric endocrine morbidity. STUDY DESIGN: A retrospective population-based cohort study compared the incidence of long-term pediatric hospitalizations due to endocrine morbidity of singleton children born SGA, appropriate-for-gestational-age (AGA), and LGA at-term. A multivariate generalized estimating equation (GEE) logistic regression model analysis was used to control for confounders. RESULTS: During the study period, 235,614 deliveries met the inclusion criteria; of which 4.7% were SGA (n = 11,062), 91% were AGA (n = 214,249), and 4.3% were LGA neonates (n = 10,303). During the follow-up period, children born SGA or LGA at-term had a significantly higher rate of long-term endocrine morbidity. Using a multivariable GEE logistic regression model, controlling for confounders, being delivered SGA or LGA at-term was found to be an independent risk factor for long-term pediatric endocrine morbidity (Adjusted OR = 1.4; 95%CI = 1.1-1.8; p = .015 and aOR = 1.4; 95%CI = 1.1-1.8; p = .005, respectively). Specifically, LGA was found an independent risk factor for overweight and obesity (aOR = 1.7; 95%CI = 1.2-2.5; p = .001), while SGA was found an independent risk factor for childhood hypothyroidism (aOR = 3.2; 95%CI = 1.8-5.8; p = .001). CONCLUSIONS: Birth weight either SGA or LGA at-term is an independent risk factor for long-term pediatric endocrine morbidity.

Elective cesarean delivery at term and the long-term risk for endocrine and metabolic morbidity of the offspring.

Other than obesity, no definitive insights have been gained regarding the apparent association between mode of delivery and long-term endocrine and metabolic outcomes in the offspring. We aimed to determine whether elective cesarean delivery (CD) impacts on long-term endocrine and metabolic morbidity of the offspring. A population-based cohort analysis was performed including all singleton-term deliveries occurring between 1991 and 2014 at a single tertiary medical center. A comparison was performed between children delivered via a non-emergent CD and those delivered vaginally (VD). Hospitalizations of the offspring up to the age of 18 years involving endocrine morbidity were evaluated. A Kaplan-Meier survival curve was used to compare cumulative morbidity incidence. Cox and a Weibull regression models were used to control for confounders. During the study period 131,880 term deliveries met the inclusion criteria; 8.9% were elective non-urgent CDs (n=11,768) and 91.1% (n=120,112) were VDs. The survival curve demonstrated a significantly higher cumulative incidence of endo-metabolic morbidity in offspring born via CD (P=0.010). In the regression models, adjusted for maternal obesity, CD was not noted as an independent risk factor for long-term pediatric endocrine and metabolic morbidity of the offspring while maternal obesity emerged as a strong predictor. We therefore conclude that CD per-se does not appear to increase the risk for long-term pediatric endo-metabolic morbidity of the offspring.

Impact of incremental circumferential resection margin distance on overall survival and recurrence in oesophageal adenocarcinoma.

BACKGROUND: Previous analyses of the oesophageal circumferential resection margin (CRM) have focused on the prognostic validity of two different definitions of a positive CRM, that of the College of American Pathologists (tumour at margin) and that of the Royal College of Pathologists (tumour within 1 mm). This study aimed to analyse the validity of these definitions and explore the risk of recurrence and survival with incremental tumour distances from the CRM. METHODS: This cohort study included patients who underwent resection for adenocarcinoma of the oesophagus between 2000 and 2014. Kaplan-Meier and Cox regression analyses were performed to determine the hazard ratio (HR) with 95 per cent confidence intervals for recurrence and mortality in CRM increments: tumour at the cut margin, extending to within 0·1-0·9, 1·0-1·9, 2·0-4·9 mm, and 5·0 mm or more from the margin. RESULTS: A total of 444 patients were included in the study. Kaplan-Meier and unadjusted analyses showed a significant incremental improvement in overall survival (P < 0·001) and recurrence (P for trend < 0·001) rates with increasing distance from the CRM. Tumour distance of 2·0 mm or more remained a significant predictor of survival on multivariable analysis (HR for risk of death 0·66, 95 per cent c.i. 0·44 to 1·00). Multivariable analysis of overall survival demonstrated a significant difference between a positive and negative CRM with the Royal College of Pathologists' definition (HR 1·37, 1·01 to 1·85), but not with the College of American Pathologists' definition (HR 1·22, 0·90 to 1·65). CONCLUSION: This study demonstrated an incremental improvement in survival and recurrence rates with increasing tumour distance from the CRM.

Incommensurability and phase transitions in two-dimensional XY models with Dzyaloshinskii-Moriya interactions.

The Dzyaloshinskii-Moriya (DM) interaction in magnetic models is the result of a combination of superexchange and spin-orbital coupling, and it can give rise to rich phase-transition behavior. In this paper, we study ferromagnetic XY models with the DM interaction on two-dimensional L×L square lattices using a hybrid Monte Carlo algorithm. To match the incommensurability between the resultant spin structure and the lattice due to the DM interaction, a fluctuating boundary condition is adopted. We also define a different kind of order parameter and use finite-size scaling to study the critical properties of this system. We find that a Kosterlitz-Thouless-like phase transition appears in this system and that the phase-transition temperature shifts toward higher temperature with increasing DM interaction strength.

UK Consensus on Normal Tissue Dose Constraints for Stereotactic Radiotherapy.

Six UK studies investigating stereotactic ablative radiotherapy (SABR) are currently open. Many of these involve the treatment of oligometastatic disease at different locations in the body. Members of all the trial management groups collaborated to generate a consensus document on appropriate organ at risk dose constraints. Values from existing but older reviews were updated using data from current studies. It is hoped that this unified approach will facilitate standardised implementation of SABR across the UK and will allow meaningful toxicity comparisons between SABR studies and internationally.

The Impact of Cardiac Radiation Dosimetry on Survival After Radiation Therapy for Non-Small Cell Lung Cancer.

PURPOSE: The heart receives high radiation doses during radiation therapy of advanced-stage lung cancer. We have explored associations between overall survival, cardiac radiation doses, and electrocardiographic (ECG) changes in patients treated in IDEAL-CRT, a trial of isotoxically escalated concurrent chemoradiation delivering tumor doses of 63 to 73 Gy. METHODS AND MATERIALS: Dosimetric and survival data were analyzed for 78 patients. The whole heart, pericardium, AV node, and walls of left and right atria (LA/RA-Wall) and ventricles (LV/RV-Wall) were outlined on radiation therapy planning scans, and differential dose-volume histograms (dDVHs) were calculated. For each structure, dDVHs were approximated using the average dDVH and the 10 highest-ranked structure-specific principal components (PCs). ECGs at baseline and 6 months after radiation therapy were analyzed for 53 patients, dichotomizing patients according to presence or absence of "any ECG change" (conduction or ischemic/pericarditis-like change). All-cause death rate (DR) was analyzed from the start of treatment using Cox regression. RESULTS: 38% of patients had ECG changes at 6 months. On univariable analysis, higher scores for LA-Wall-PC6, Heart-PC6, "any ECG change," and larger planning target volume (PTV) were significantly associated with higher DR (P=.003, .009, .029, and .037, respectively). Heart-PC6 and LA-Wall-PC6 represent larger volumes of whole heart and left atrial wall receiving 63 to 69 Gy. Cardiac doses ≥63 Gy were concentrated in the LA-Wall, and consequently Heart-PC6 was highly correlated with LA-Wall-PC6. "Any ECG change," LA-Wall-PC6 scores, and PTV size were retained in the multivariable model. CONCLUSIONS: We found associations between higher DR and conduction or ischemic/pericarditis-like changes on ECG at 6 months, and between higher DR and higher Heart-PC6 or LA-Wall-PC6 scores, which are closely related to heart or left atrial wall volumes receiving 63 to 69 Gy in this small cohort of patients.