Two-dimensional projected-momentum covariance mapping for coulomb explosion imaging

We introduce projected-momentum covariance mapping, an extension of recoil-frame covariance mapping for 2D ion imaging studies. By considering the two-dimensional projection of the ion momenta as recorded by the detector, one opens the door to a complex suite of analysis tools adapted from three-dimensional momentum imaging studies. This includes the use of different frames of reference to unravel the dynamics of fragmentation and the application of fragment momentum constraints to isolate specific fragmentation channels. The technique is demonstrated on data from a two-dimensional ion imaging study of the Coulomb explosion of the cis and trans isomers of 1,2-dichloroethene, following strong-field ionization by an intense near-infrared femtosecond laser pulse. Classical simulations are used to guide the interpretation of projected-momentum covariance maps. The results offer a detailed insight into the distinct Coulomb explosion dynamics for this pair of isomers and lay the groundwork for future time-resolved studies of photoisomerization dynamics in this molecular system

Extension of lymphadenectomy for gastric cancer:Audit at European specialist centres.

Gastric cancer is still one of the leading causes of cancer-related deaths worldwide, and its treatment management differs between Eastern Asia and Western countries. Screening program, early diagnosis, and surgical treatment was primarily established in Japan and was rapidly disseminated to other countries. In other parts of the world, such as the USA and Western Europe, the incidence of gastric cancer has declined, and efforts for screening and early detection have not been an issue of higher priority over the management of other diseases. Thus, gastric cancer in the West is often more advanced and is either inoperable or needs more radical surgery for resection. The only treatment method that can potentially cure gastric cancer is the surgical approach. Depending on the extension of the tumor, surgeons may execute an operation that involves removing all or part of the stomach with some nearby lymph nodes (lymphadenectomy). Lymphadenectomy is a crucial step during surgical operation that involves the removal of one or more lymph nodes located in the drainage area of a tumor, in which there is a high possibility of lymph node metastasis. The Japanese guidelines define the criteria of lymphadenectomy procedure into D1 D1+ or D2 according to the type of gastrectomy executed. The extent of lymphadenectomy has long been a subject of debate. Indeed, Japanese surgeons introduced extended lymphadenectomy (D2), which has also been progressively adopted in Europe and included in almost all international guidelines. However, the procedure requires a long learning curve, which involves a high volume of interventions; therefore, US guidelines do not recommend the D2, and many Italian and European centres do not yet perform this procedure. Indeed, the current European Consensus guidelines recommend D2 dissection in regional specialist centres for patients with moderate comorbidity. However, compliance with guidelines is unclear, and in some recent RCTs, the standard approach of surgical treatment is at the "surgeon's discretion." This study aims to evaluate the current practice of D2 lymphadenectomy in Europe to determine any variation in practice and compare it with the Japanese guidelines. The study consists of two parts: first, a questionnaire based on hypothetical clinical scenarios was administered to expert surgeons belonging to European Chapter of the International Gastric Cancer Association from high-volume European centers. They were asked to select the appropriate lymphadenectomy extension for each hypothetical case and the associated lymph node stations to remove. In the second part of the study, the same surgeons were asked to collect their data about gastric cancer gastrectomies performed in 2015 for comparative analysis. The study results show that the expert surgeons of high-volume centres are quite in agreement with the choice of D2 lymphadenectomy in the different clinical scenarios. The surgical choice seems to have been influenced by the tumor stage, site, and histology of the tumor. More specifically, the D2 procedure is recommended for cases with diffuse histology compared to tumors with intestinal histology. However, the selection of the D2 dissection procedure rarely conformed to Japanese guidelines: the choice of lymph node stations revealed the presence of a wide variation in execution. In the review of the gastrectomy experience, it was observed that a high surgical standard was achieved: in fact, in 97% of gastric cancer gastrectomies after D2, an adequate number of lymph nodes (≥15 nodes) were removed. In conclusion, even if an adequate lymphadenectomy was obtained in almost all cases in dedicated centers, there is still significant variability in the number of recovered lymph nodes. The histology of the tumor largely influences the surgeon's choice regarding the extent of the lymphadenectomy; however, the role of histology in the planning of surgical procedures is not considered in the current guidelines and must be verified in prospective studies

Is fall prevention by vitamin D mediated by a change in postural or dynamic balance?

Introduction: The objectives were:(1) to validate a quantitative balance assessment method for fall risk prediction; (2) to investigate whether the effect of vitamin D and calcium on the risk of falling is mediated through postural or dynamic balance, as assessed by this method. Materials and methods: A secondary analysis of a double blind randomized controlled trial was employed, which included 64 institutionalized elderly women with complete balance assessment (age range: 65-97; mean 25-hydroxyvitamin D levels: 16.4ng/ml (SD ±9.9). Participants received 1,200mg calcium plus 800IU cholecalciferol (n=33) or 1,200mg calcium (n=31) per day over a 3-month treatment period. Using an electronic device attached to the lower back of the participant, balance was assessed as the degree of trunk angular displacement and angular velocity during a postural task (standing on two legs, eyes open, for 20 s) and a dynamic task (get up from a standard height chair with arm rests, sit down and then stand up again and remain standing). Results: It was found that both postural and dynamic balance independently and significantly predicted the rate of falling within the 3-month follow-up. Vitamin D plus calcium reduced the rate of falls by 60% [relative risk (RR)=0.40; 95% CI: 0.17, 0.94] if compared with calcium alone. Once postural and dynamic balance were added to the regression analysis, they both attenuated the effect of vitamin D plus calcium on the rate of falls. For postural balance, the RR changed by 22% from 0.40 to 0.62 if angular displacement was added to the model, and by 9% from 0.40 to 0.49 if angular velocity was added. For dynamic balance, it changed by 1% from 0.40 to 0.41 if angular displacement was added, and by 14% from 0.40 to 0.54 if angular velocity was added. Discussion: Thus, balance assessment using trunk angular displacement is a valid method for the prediction of falls in older women. Of the observed 60% reduction in the rate of falls by vitamin D plus calcium supplementation compared with calcium alone, up to 22% of the treatment effect was explained by a change in postural balance and up to 14% by dynamic balanc

Pathological prognostic factors in the second British Stomach Cancer Group trial of adjuvant therapy in resectable gastric cancer.

The second British Stomach Cancer Group trial was a prospective randomised controlled trial of adjuvant radiotherapy or cytotoxic chemotherapy after gastrectomy for adenocarcinoma. It recruited between 1981 and 1986. No survival advantage has been demonstrated for the patients receiving either type of adjuvant therapy compared with those undergoing surgery alone. We report on 436 patients randomised into the trial together with 203 patients, who did not fulfil the trial criteria, referred to the trial. A univariate (log-rank) analysis of pathological factors obtained from the local referring centres showed that tumour size, macroscopic type, number os sites involved, depth of invasion, involvement of resection lines and lymph nodes and histological grade were significant determinants of survival. Histological review by two experienced histopathologists found that the Lauren classification and histological grade, but not the Ming classification, were significant prognostic factors. The degree of lymphocytic and eosinophilic infiltration and presence of dysplasia assessed by one of the pathologists showed a significant correlation with survival. However, inter-observer correlation for these histological parameters and grade was poor. Multivariate analysis identified only depth of invasion, resection line and nodal involvement as significant independent pathological variables influencing survival. This study confirms the need for expert preparation of the resected specimen to obtain the important information on depth of invasion and nodal status and also reveals some variation in histological assessment, particularly grading, in gastric carcinoma

Automated detection and delineation of lymph nodes in haematoxylin & eosin stained digitised slides.

Treatment of patients with oesophageal and gastric cancer (OeGC) is guided by disease stage, patient performance status and preferences. Lymph node (LN) status is one of the strongest prognostic factors for OeGC patients. However, survival varies between patients with the same disease stage and LN status. We recently showed that LN size from patients with OeGC might also have prognostic value, thus making delineations of LNs essential for size estimation and the extraction of other imaging biomarkers. We hypothesized that a machine learning workflow is able to: (1) find digital H&E stained slides containing LNs, (2) create a scoring system providing degrees of certainty for the results, and (3) delineate LNs in those images. To train and validate the pipeline, we used 1695 H&E slides from the OE02 trial. The dataset was divided into training (80%) and validation (20%). The model was tested on an external dataset of 826 H&E slides from the OE05 trial. U-Net architecture was used to generate prediction maps from which predefined features were extracted. These features were subsequently used to train an XGBoost model to determine if a region truly contained a LN. With our innovative method, the balanced accuracies of the LN detection were 0.93 on the validation dataset (0.83 on the test dataset) compared to 0.81 (0.81) on the validation (test) datasets when using the standard method of thresholding U-Net predictions to arrive at a binary mask. Our method allowed for the creation of an "uncertain" category, and partly limited false-positive predictions on the external dataset. The mean Dice score was 0.73 (0.60) per-image and 0.66 (0.48) per-LN for the validation (test) datasets. Our pipeline detects images with LNs more accurately than conventional methods, and high-throughput delineation of LNs can facilitate future LN content analyses of large datasets

Periodically-dressed Bose-Einstein condensates: a superfluid with an anisotropic and variable critical velocity

Two intersecting laser beams can produce a spatially-periodic coupling between two components of an atomic gas and thereby modify the dispersion relation of the gas according to a dressed-state formalism. Properties of a Bose-Einstein condensate of such a gas are strongly affected by this modification. A Bogoliubov transformation is presented which accounts for interparticle interactions to obtain the quasiparticle excitation spectrum in such a condensate. The Landau critical velocity is found to be anisotropic and can be widely tuned by varying properties of the dressing laser beams.Comment: 5 pages, 4 figure