Measuring the Dispersion Forces Near the van der Waals-Casimir Transition

Forces induced by quantum fluctuations of the electromagnetic field control adhesion phenomena between rough solids when the bodies are separated by distances of approximately 10 nm. However, this distance range remains largely unexplored experimentally in contrast with the shorter (van der Waals forces) or the longer (Casimir forces) separations. The reason for this is the pull-in instability of the systems with the elastic suspension that poses a formidable limitation. In this paper we propose a genuine experimental configuration that does not suffer from the short distance instability. The method is based on the adhered cantilever, whose shape is sensitive to the forces acting near the adhered end. The general principle of the method, its possible realization, and feasibility are extensively discussed. The dimensions of the cantilever are determined by the maximum sensitivity to the forces. If the adhesion is defined by strong capillary or chemical interactions, the method loses its sensitivity. Special discussion is presented for the determination of the minimum distance between the rough solids upon contact, and for the compensation of the residual electrostatic contribution. The proposed method can be applied to any kind of solids (metals, semiconductors, or dielectrics) and to any intervening medium (gas or liquid).</p

Excessive number of high asperities for sputtered rough films

The roughness of solids is crucial for interactions between bodies at short separations due to capillary or van der Waals-Casimir forces and for contact mechanics. Specifically, it is critical for the fabrication and operation of microelectromechanical systems, for which functional materials are deposited using thin film coating technologies. Here, it is demonstrated that the materials deposited by magnetron sputtering or thermally evaporated on a cold Si substrate reveal a significantly larger number of high asperities than that predicted by the normal distribution. Such asperities define the distance between the solids in contact that is the key parameter for many problems. The effect is related to the nonequilibrium deposition conditions and is suppressed if the material is deposited on a hot substrate or annealed. The high asperity tails can be described by the extreme value distribution or in some cases by the exponential distribution

Herbivore effect traits and their impact on plant community biomass: an experimental test using grasshoppers

1. Using trait-based approaches to study trophic interactions may represent one of the most promising approaches to evaluate the impact of trophic interactions on ecosystem functioning. To achieve this goal, it is necessary to clearly identify which traits determine the impact of one trophic level on another.2. Using functionally contrasting grasshopper species, we tested the ability of multiple traits (morphological, chemical and biomechanical) to predict herbivore impact on the biomass of a diverse plant community. We set up a cage experiment in an old species rich grassland field and evaluated how multiple candidate grasshopper effect traits mediated herbivore impact on plant biomass.3. Grasshoppers had different impact on plant community biomass (consuming up to 60 % of plant community biomass). Grasshopper impact was positively correlated with their incisive strength while body size or grasshopper C:N ratio exhibited low predictive ability. Importantly, the strong relationship between the incisive strength and the impact was mediated by the grasshopper feeding niche, which was well predicted in our study by two simple plant traits (leaf dry matter content, leaf C:N ratio). Feeding niche differences between grasshoppers were explained by differences in incisive strength, highlighting the fundamental linkage between grasshopper effect traits and their niche.4. Our study contributes to the development of the trait-based approach in the study of trophic interactions by providing a first experimental test of the relationship between herbivore effect traits, their impact on plant community biomass, and in a larger extent on ecosystem functioning. By comparing the relative importance of multiple interacting grasshopper traits, our study showed that incisive strength was a key effect trait which determined grasshopper feeding niche and its relative impact on plant community biomass

Comparative analysis of outcome predictors in patients with postoperative peritonitis depending on the method of surgical treatment – relaparotomy on demand vs vacuum-assisted laparostomy

Background: Secondary postoperative diffuse peritonitis (SPDP) is one of the most severe complications of elective and emergency surgical interventions associated with a high mortality rate. To date, no optimal tactics of surgical treatment of SPDP has been developed.Objective: The analysis of independent predictors of outcome depending on the method of surgical treatment – relaparotomy ondemand (RD) or vacuum-assisted laparostomy (VAL).Material and methods: The study included 141 adult patients, male and female in the period from January 2014 to December 2020: group I (n = 63) – patients who received VAL method; group II (n = 78) – RD method. The method of multivariate logistic regression analysis was used to calculate the independent effects of potential predictor variables on the treatment outcome.Results: The following independent predictors of treatment outcome in the RD group were identified: age, duration of hospital stay, number of relaparotomies, APACHE II score, Björck classification grade 1C at the 1st sanitation, bacteremia, Clavien–Dindo complications class 3a and 4a. For the VAL group: conversion of surgical tactics and bacteremia.Conclusion: In patients with SPDP in the presence of risk factors for unfavorable outcomes, the use of VAL with staged sanitation of the abdominal cavity is indicated

Comparative evaluation of reconstructive procedures after gastrectomy with and without duodenal passage preservation in gastric cancer: a systematic review and meta-analysis

Background. Optimal reconstruction after gastrectomy (GE) in gastric cancer (GC) is currently a pressing issue, with research continuing to advance functional methods, especially those preserving duodenal passage, to improve the patient’s quality of life (QOL) and nutritional status (NS).Objectives. An evaluation of randomised clinical trials (RCTs) targeting GC patients with radical GE and comparing duodenal passage-preserving (DPP) and non-preserving (NDPP) reconstruction techniques in terms of immediate outcomes, post-gastrectomy syndrome, NS and QOL.Methods. Sources were mined in the PubMed, Cochrane Library, Google Scholar electronic databases, as well as CyberLeninka and eLibrary national resources. The RCTs meeting eligibility criteria (15 publications) were covered in a meta-analysis. Outcome variations were defined via odds ratio (OR), standard error estimated with 95% CI, statistical significance was assumed at p &lt;0.05. Review Manager (RevMan v. 5.4., the Cochrane Collaboration, 2020) was used for statistical data processing.Results. A total of 15 RCTs were surveyed (1,766 patients; 722 in DPP and 1,044 in NDPP cohort). The complication and mortality rates did not differ significantly between cohorts. The meta-analysis elicited a significant advantage of DPP-GE regarding the dumping syndrome incidence at all post-surgery terms cumulatively (OR = 0.32 [95% CI: 0.22–0.48], p = 0.00001), as well as the 3- and 12-month terms, with no difference observed for 24 months. No statistically significant DPP vs. NDPP cohort variations have been found regarding reflux, stasis syndrome or NS values. The RCTs were evidently diverse with respect to QOL assessment techniques; 4 of 7 publications reported DPP advantages, and 3 — no significant variation in QOL between the DPP and NDPP cohorts.Conclusion. Further research is necessary to substantiate optimal reconstruction methods, particularly those restoring food passage through duodenum after GE, to facilitate the patient’s most favourable QOL and NS

Vacuum-assisted laparostomy with staged peritoneal lavage in management of secondary postoperative diffuse peritonitis: a prospective comparative non-randomised clinical trial

Background. Secondary postoperative diffuse peritonitis (SPDP) associates with a high incidence of abdominal sepsis and 35–92% mortality rate. An optimal surgical doctrine in this complication in lacking to date.Objectives. An efficacy assessment of vacuum-assisted laparostomy (VAL) with staged lavage relative to relaparotomy on demand (RD) in SPDP patients.Methods. Patient enrolment and analyses were conducted within period 01.11.2017-31.12.2020, totalling for 141 SPDP patients, 77 (54.6%) males and 64 (45.4%) females aged 64.5 (5972.7) years. Cohort I patients (n = 52) had post-abdominal-lavage VAL using Suprasorb® SNP (SNP-1 and SNP-2) equipment and consumables (Lohmann &amp; Rauscher GmbH, Austria). Staged lavage was performed 48-72 h apart. Cohort II (n = 78) had a standard RD  technique. Cohort III (n = 11) treatment included RD-to-VAL transition. The endpoint was the inpatient treatment outcome, a favourable completion or death. The additional estimated criteria were complications rate and severity (in ACCORDION-modified Clavien-Dindo classification), sepsis rate, C-reactive protein level, abdominal index dynamics, patient’s intensive-care and total-hospital lengths of stay.Results. Cohort I included 157 staged-lavage VALs, cohort II — 107 RDs, cohort III — 49 operations. The mortality rate was 3/52 (5.8%), 24/78 (30.8%) and 7/11 (63.6%) in cohorts I, II and III (respectively, p &lt; 0.001). No difference was observed in the length of hospital stay, with a shorter intensive care stay after final abdominal closure in cohort I. Clavien — Dindo grade 3a complications were observed for 25.0% of cohort I, 60.3 and 45.5% — of cohorts II and III (respectively, p &lt; 0.01); grade 3b complications were 0 (0%), 24.4 and 100% in cohorts I, II and III (respectively, p &lt; 0.001; all 11 patients were reoperated). Multiple organ failure (grade 4b) was reported in 5.8, 30.8 and 63.6% of cohorts I, II and III (respectively, p &lt; 0.001). By end of treatment, sepsis had resolved in 9/11 (81.8%) patients in cohort I, 5/24 (20.8%) and 1/6 (16.7%) — in cohorts II and III (respectively, p = 0.002).Conclusion. Programmed staged-lavage VAL is an optimal surgical treatment tactics in SPDP. Relative to RD, VAL provides a more effective management of local and systemic abdominal sepsis, lower mortality, fewer and less sever complications, shorter intensive care stays after abdominal closure

(Super)twistors and (super)strings

The Lagrangian formulation of the D=4 bosonic string and superstring in terms of the (super)twistors is considered. The (super)twistor form of the equations of motion is derived and the kappa-symmetry transformation for the supertwistors is given. It is shown that the covariant kappa-symmetry gauge fixation results in the action quadratic in the (super)twistor variables.Comment: LaTeX, 17 page