Often, the interpretation of experiments concerning the manipulation of the energy distribution of laser-accelerated ion bunches is complicated by the multitude of competing dynamic processes ...simultaneously contributing to recorded ion signals. Here we demonstrate experimentally the acceleration of a clean proton bunch. This was achieved with a microscopic and three-dimensionally confined near critical density plasma, which evolves from a 1 µm diameter plastic sphere, which is levitated and positioned with micrometer precision in the focus of a Petawatt laser pulse. The emitted proton bunch is reproducibly observed with central energies between 20 and 40 MeV and narrow energy spread (down to 25%) showing almost no low-energetic background. Together with three-dimensional particle-in-cell simulations we track the complete acceleration process, evidencing the transition from organized acceleration to Coulomb repulsion. This reveals limitations of current high power lasers and viable paths to optimize laser-driven ion sources.
Supramolecular copolymers formed by the noncovalent synthesis of multiple components expand the complexity of functional molecular systems. However, varying the composition and microstructure of ...copolymers through tuning the interactions between building blocks remains a challenge. Here, we report a remarkable discovery of the temperature-dependent supramolecular copolymerization of the two chiral monomers 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzamide ( S -T) and 4,4′,4″-(benzene-1,3,5-triyl)tribenzamide ( S -B). We first demonstrate in the homopolymerization of the two individual monomers that a subtle change from the central triazine to benzene in the chemical structure of the monomers significantly affects the properties of the resulting homopolymers in solution. Homopolymers formed by S -T exhibit enhanced stability in comparison to S -B. More importantly, through a combination of spectroscopic analysis and theoretical simulation, we reveal the complex process of copolymerization: S -T aggregates into homopolymers at elevated temperature, and upon slow cooling S -B gradually intercalates into the copolymers, to finally give copolymers with almost 80% alternating bonds at 10 °C. The formation of the predominantly alternating copolymers is plausibly contributed by preferred heterointeractions between triazine and benzene cores in S -T and S -B, respectively, at lower temperatures. Overall, this work unravels the complexity of a supramolecular copolymerization process where an intermediate heterointeraction (higher than one homointeraction and lower than the other homointeraction) presents and proposes a general method to elucidate the microstructures of copolymers responsive to temperature changes.
As with endoscopic transmural drainage of peripancreatic fluid collections, the same transluminal access can be expanded to introduce an endoscope through the gastrointestinal wall into the ...retroperitoneum and remove infected pancreatic necroses under direct visual control. This study reports the first large series with long-term follow-up.
Data for all patients undergoing transluminal endoscopic removal of (peri)pancreatic necroses between 1999 and 2005 in six different centres were collected retrospectively, and the patients were followed up prospectively until 2008. The initial patient and treatment outcome data were recorded, as were long-term results.
Ninety-three patients (63 men, 30 women; mean age 57 years) underwent a mean of six interventions starting at a mean of 43 days after an attack of severe acute pancreatitis. After establishment of transluminal access to the necrotic cavity and subsequent endoscopic necrosectomy, initial clinical success was obtained in 80% of the patients, with a 26% complication and a 7.5% mortality rate at 30 days. After a mean follow-up period of 43 months, 84% of the initially successfully treated patients had sustained clinical improvement, with 10% receiving further endoscopic and 4% receiving surgical treatment for recurrent cavities; 16% suffered recurrent pancreatitis.
Direct transluminal endoscopic removal of pancreatic necroses is associated with good long-term maintenance of the high initial efficacy; complications can occur, with an associated mortality of around 7.5%. Further studies are necessary in order to optimise endotherapy and define its role in relation to surgery in the clinical management of such patients.
Screening colonoscopy with polypectomy has been shown to reduce the morbidity and mortality associated with colorectal cancer. However, there is a lack of large and systematic prospective studies of ...the complications of polypectomy.
Data on all snare polypectomies performed in 13 institutions (six hospitals and seven gastroenterology offices) were recorded prospectively during a 20-month period, including data on a 30-day follow-up period. The primary end points of the study were polypectomy complications, which were classed as "major" or "minor". Risk factors for complications were analyzed for both patient characteristics and polyp parameters.
A total of 3976 snare polypectomies in 2257 patients (mean age 64.5 years) were included in the study. The mean polyp size was 1.1 cm, and 72% were sessile. Complications occurred in 9.7% of patients (6.1% of polyps); 75% of these complications were minor; and the mortality rate was zero. Multivariate regression analysis revealed polyp size as the main risk factor, both for complications overall (odds ratio 6.56, 95%CI 4.45-9.67) and for major complications (odds ratio 31.01, 95%CI 7.53-128.1). Right-sided polyp location was a significant risk factor for major complications (odds ratio 2.40, 95%CI 1.34-4.28). Setting a cut-off value of 3% as an acceptable rate for major complications, polyps larger than 1 cm in the right colon or 2 cm in the left colon, and multiple polyps carried an increased risk.
Colonoscopic polypectomy is associated with a 10% rate of complications, but three-quarters of these are of minor clinical significance. More than 90% of the complications can be managed conservatively if adequate endoscopic expertise is available. Guidelines for intensified follow-up after polypectomy should be based on the size, location, and number of a patient's polyps.
The biggest challenge in endoscopic surveillance of Barrett's oesophagus is better detection of neoplasia in mucosa of normal macroscopic appearance. We evaluated in vivo miniprobe confocal laser ...microscopy (CLM) for the detection of invisible Barrett's neoplasia.
Prospective two-centre trial in two phases: phase I to establish criteria of Barrett's neoplasia and phase II to test these criteria.
296 biopsy sites in 38 consecutive patients with Barrett's oesophagus (mean age 62.1 years, 89.5% men, median length of the Barrett's oesophagus, 3 cm) were examined with standard high-resolution endoscopy and by miniprobe CLM, with precise matching of CLM recordings to biopsy sites. CLM image criteria for normal versus neoplastic Barrett's oesophagus were established from 95 biopsies of 15 patients (phase I); these criteria were then prospectively tested on 201 biopsies from the remaining patients without visible focal changes (phase II). All 201 CLM video recordings from phase II cases were randomised and blindly evaluated by two gastroenterologists.
The primary endpoints were accuracy values in diagnosing HGIN or early carcinoma (EC) on a per-biopsy basis. Secondary endpoints included inter-observer agreement.
All initially defined miniprobe CLM criteria (phase I) were significantly more frequently detected in HGIN/EC sites compared with sites with no or low grade neoplasia (phase II). In a per-biopsy analysis, sensitivity and specificity for two independent investigators were 75.0% and 88.8%, and 75.0% and 91.0%, respectively, translating at best into a positive predictive value of 44.4% and a negative predictive value of 98.8%. Inter-observer agreement was good (kappa 0.6).
Miniprobe CLM showed a high negative predictive value for the diagnosis of endoscopically invisible neoplasia in Barrett's oesophagus; sensitivity, however, has still to be improved.
Peroral endoscopic myotomy for achalasia Bredenoord, A. J.; Rösch, T.; Fockens, P.
Neurogastroenterology & motility/Neurogastroenterology and motility,
January 2014, Letnik:
26, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Background
Treatment of achalasia is complicated by symptom recurrence and a significant risk for severe complications. Endoscopic myotomy was developed in the search for a highly efficacious ...treatment with lower risks. Since its introduction in 2010, several centers have adopted the technique and published excellent short‐term results of open label series. Randomized trials with long‐term endpoint comparing per‐oral endoscopic myotomy (POEM) with the established treatments such as balloon dilation and surgical myotomy are now warranted, before POEM can be regarded as the routine clinical care for achalasia patients.
Purpose
This review describes the development, technical aspects, efficacy, and complications of POEM.
Endoscopic myotomy was developed in the search for a highly efficacious treatment with lower risks. Since its introduction in 2010, several centers have adopted the technique and published excellent short‐term results of open label series. This review describes the development, technical aspects, efficacy, and complications of POEM.
Endoscopic mucosal resection (EMR) of early gastrointestinal cancers has been shown to be effective in treating mucosal malignancies, but en bloc resection (where the entire tumor is removed in one ...piece) is often not achieved using conventional cap EMR. Other techniques, developed in Japan, include the application of different types of knife such as the insulated-tip instrument. We report our preliminary experience of the use of this knife, in conjunction with other techniques, in attempting en bloc resection of early mucosal cancers and adenomas and in the removal of submucosal tumors (SMTs) of the upper gastrointestinal tract.
A total of 37 patients (26 men, 11 women, age range 53 - 86) were included in the study; 23 patients had 24 mucosal lesions amenable to EMR, and 14 patients had SMTs shown on endosonography to spare the muscularis propria. Lesions were located in the esophagus (n = 13), the stomach (n = 24), and the duodenum (n = 1); 40 % of the mucosal lesions were 20 mm or larger (mean size 18mm), whereas the mean size of the submucosal lesions was 23 mm. After submucosal saline injection, circumcision and dissection of the mucosal lesions was attempted with the aim of achieving en bloc resection. For SMTs, cap mucosectomy of the overlying mucosa was done first, and the tumors were then freed using saline injection, and finally resected using snare polypectomy.
The strict aim of the study, i. e. complete tumor removal in a single piece, was achieved in only 25 % of the mucosal lesions (some failures were due to unrecognized submucosal infiltration) and 36 % of the SMTs. When a more liberal definition of success was assumed, this rate increased to 65 % for mucosal lesions (piecemeal, no tumor found at surgery or follow-up endoscopy with biopsy) and 79 % for SMTs (piecemeal). No severe complications necessitating surgery or leading to major morbidity occurred. However, clinically significant complications were found in six patients (minor perforation managed conservatively (n = 1), severe pain without perforation (n = 1), bleeding requiring reintervention (n = 3), and aspiration (n = 1)).
Although we are convinced that methods of achieving en bloc resection of mucosal cancers and SMTs must be pursued, the insulated-tip knife in conjunction with conventional endoscopes still has limitations. Innovative endoscope design (double-channel scopes) as well as the development of new accessories will help to overcome the current limitations and further promote endoscopic tumor resection.
The conformational analysis of a 2,4-bis(4-dialkylamino-2-amido)phenyl squaraine dye revealed the presence of two rotational isomers at room temperature. Combination of spectroscopic and ...computational techniques showed that the rotational barrier is influenced by hydrogen bonds between the amido substituents and the oxygen atoms at the quadratic core. Even small amounts of trifluoroacetic acid interfered with the intramolecular hydrogen bond formation and accelerated the interconversion of the conformers.
Colonoscopy is an established method of colorectal cancer screening, but has an adenoma miss rate of 10-20%. Detection rates are expected to improve with optimised visualisation methods. This ...prospective randomised study evaluated narrow-band imaging (NBI), a new technique that may enhance image contrast in colon adenoma detection.
Eligible patients presenting for diagnostic colonoscopy were randomly assigned to undergo wide-angle colonoscopy using either conventional high-resolution imaging or NBI during instrument withdrawal. The primary outcome parameter was the difference in the adenoma detection rate between the two techniques.
A total of 401 patients were included (mean age 59.4 years, 52.6% men). Adenomas were detected more frequently in the NBI group (23%) than in the control group (17%) with a number of 17 colonoscopies needed to find one additional adenoma patient; however, the difference was not statistically significant (p = 0.129). When the two techniques were compared in consecutive subgroups of 100 study patients, adenoma rates in the NBI group remained fairly stable, whereas these rates steadily increased in the control group (8%, 15%, 17%, and 26.5%, respectively). Significant differences in the first 100 cases (26.5% versus 8%; p = 0.02) could not be maintained in the last 100 cases (25.5% versus 26.5%, p = 0.91).
The increased adenoma detection rate means of NBI colonoscopy were statistically not significant. It remains speculative as to whether the increasing adenoma rate in the conventional group may have been caused by a training effect of better polyp recognition on NBI.
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