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The EROI is one of the most important indices to evaluate the net energy output of a source of primary energy (there is a lively debate on the usability of this kind of parameter, but here we will use it under the hypothesis that it is a good way to establish if an oil company has a level of efficiency close to other energetic sources). It is generally defined as the ratio between the energy extracted by a given resource and the energy costs sustained to extract that energy. We tried to set up an alternative method for the calculation of the EROI, taking (1) as a proxy of the energy costs the available data about the CO2 emissions of the oil companies, as reported in the sustainability reports (SRs), recommended by the international organisms such as IPCC and WBCSD, although not mandatory, and (2) as a proxy of the energy extracted the CO2 emissions estimate obtained by a stoichiometric conversion of the oil/gas production declared by the oil companies. Both proxies have been also corrected to take into account the different CO2 emission rate per unit energy of oil and gas. The resulting estimates of EROI are rather homogeneous and not too different from the values reported in the literature. The method could be suitable for year-by-year comparison of the time evolution of this important energy quality parameter for the individual energy-producing and energy-delivering companies.

Background Foreign body (FB) impaction accounts for 4% of emergency endoscopies in clinical practice. Flexible endoscopy (FE) is recommended as the first-line therapeutic option because it can be performed under sedation, is cost-effective, and is well tolerated. Rigid endoscopy (RE) under general anesthesia is less used but may be advantageous in some circumstances. The aim of the study was to compare the efficacy and safety of FE and RE in esophageal FB removal. Methods PubMed, MEDLINE, Embase, and Cochrane databases were consulted matching the terms “Rigid endoscopy AND Flexible endoscopy AND foreign bod*”. Pooled effect measures were calculated using an inverse-variance weighted or Mantel-Haenszel in random effects meta-analysis. Heterogeneity was evaluated using I 2 index and Cochrane Q test. Results Five observational cohort studies, published between 1993 and 2015, matched the inclusion criteria. One thousand four hundred and two patients were included; FE was performed in 736 patients and RE in 666. Overall, 101 (7.2%) complications occurred. The most frequent complications were mucosal erosion (26.7%), mucosal edema (18.8%), and iatrogenic esophageal perforations (10.9%). Compared to FE, the estimated RE pooled success OR was 1.00 (95% CI 0.48–2.06; p = 1.00). The pooled OR of iatrogenic perforation, other complications, and overall complications were 2.87 (95% CI 0.96–8.61; p = 0.06), 1.09 (95% CI 0.38–3.18; p = 0.87), and 1.50 (95% CI 0.53–4.25; p = 0.44), respectively. There was no mortality. Conclusions FE and RE are equally safe and effective for the removal of esophageal FB. To provide a tailored or crossover approach, patients should be managed in multidisciplinary centers where expertise in RE is also available. Formal training and certification in RE should probably be re-evaluated.

Foreign body ingestion is a common event; in the adult population, most ingestions occur in patients with mental disability, psychiatric disorders, alcohol intoxication or in prisoners seeking secondary gain. Removal through flexible endoscopy is generally the first-line approach but rescue oesophagotomy may be necessary for foreign bodies impacted in the upper oesophagus. A 27-year-old man was admitted in the emergency room after intentional ingestion of a wooden spherical object with a central hole. A total body CT scan showed that the object was completely obstructing the upper oesophageal lumen but there were no signs of perforation. In the operating room, a Weerda diverticuloscope and a 5 mm 0° telescope were used to visualise the foreign body under general anaesthesia. A standard endoscopic biopsy forceps was passed through the hole of the sphere and was retracted with the jaws open allowing transoral extraction without complications.

Achalasia is a rare disease characterized by impaired lower esophageal sphincter relaxation loss and of peristalsis in the esophageal body. Endoscopic balloon dilation and laparoscopic surgical myotomy have been established as initial treatment modalities. Indications and outcomes of esophagectomy in the management of end-stage achalasia are less defined. A literature search was conducted to identify all reports on esophagectomy for end-stage achalasia between 1987 and 2017. MEDLINE, Embase, and Cochrane databases were consulted matching the terms "achalasia," "end-stage achalasia," "esophagectomy," and "esophageal resection." Seventeen articles met the inclusion criteria and 1422 patients were included in this narrative review. Most of the patients had previous multiple endoscopic and/or surgical treatments. Esophagectomy was performed through a transthoracic (74%) or a transhiatal (26%) approach. A thoracoscopic approach was used in a minority of patients and seemed to be safe and effective. In 95 per cent of patients, the stomach was used as an esophageal substitute. The mean postoperative morbidity rate was 27.1 per cent and the mortality rate 2.1 per cent. Symptom resolution was reported in 75 to 100 per cent of patients over a mean follow-up of 43 months. Only five series including 195 patients assessed the long-term follow-up (5 years) after reconstruction with gastric or colon conduits, and the results seem similar. Esophagectomy for end-stage achalasia is safe and effective in tertiary referral centers. A thoracoscopic approach is a feasible and safe alternative to thoracotomy and may replace the transhiatal route in the future.

Background: Laparoscopic surgery has proven safe and effective in the treatment of large hiatus hernia. Differences may exist between objectively assessed surgical outcomes, symptomatic scores, and patient-reported outcomes. Methods: An observational, single-arm cohort study was conducted in patients undergoing primary laparoscopic repair with crura mesh augmentation and Toupet fundoplication for large (> 50% of intrathoracic stomach) type III–IV hiatus hernia. Data were extracted from hospital charts and a prospectively updated research database. The main study outcome was quality of life assessed by the Gastroesophageal reflux disease Health-Related Quality of Life (GERD-HRQL) score and the Short-form 36 (SF-36). Results: Between 2013 and 2016, 37 out of 49 operated patients completed the comprehensive quality-of-life evaluation at the 2-year follow-up. The GERD-HRQL score significantly decreased compared to baseline (p < 0.001). All items of the SF-36 significantly improved compared to baseline (p < 0.05). Both Physical and Mental Component Summary scores were significantly higher than preoperative scores, with a medium Cohen’s effect size (–0.77 and 0.56, respectively). At the 2-year follow-up, symptoms had disappeared in the majority of patients. The use of proton-pump inhibitors significantly decreased compared to baseline (13.5 vs. 86.4%, p < 0.001). Also, the use of antidepressants and benzodiazepines significantly decreased after surgery (8.1 vs. 32.4%, p < 0.001). The overall alimentary satisfaction score was > 8 in 92% of patients. There were no safety issues related to the use of the absorbable synthetic mesh. The incidence of anatomical hernia recurrence was 5.4%, but no patient with recurrent hernia required surgical revision. Conclusions: Laparoscopic repair of large hiatus hernia with mesh and partial fundoplication is associated with symptomatic relief, no side-effects, and a significant improvement in disease-specific and generic quality of life at 2-year follow-up.

The focus of this review is on leiomyoma, GIST, and extramural cysts of the esophagus. Over the last decades there has been an increasing trend in the prevalence of these lesions, mostly due to improved diagnostic accuracy. We outline the clinical presentation, the indications for treatment, and the minimally invasive surgical techniques.

It remains unclear whether the timing of neurosurgical intervention impacts the outcome of patients with isolated severe traumatic brain injury (TBI). We hypothesized that a shorter time between emergency department (ED) admission to neurosurgical intervention would be associated with a significantly higher rate of patient survival.Our institutional trauma registry was queried for patients (2003-2013) who required an emergent neurosurgical intervention (craniotomy, craniectomy) for TBI within 300 minutes after the ED admission. We included patients with altered mental status upon presentation in the ED (Glasgow Coma Scale [GCS] score9). Patients with associated severe injuries (Abbreviated Injury Scale [AIS] score ≥ 2) in other body regions were excluded. In-hospital mortality of patients who underwent surgery in less than 200 minutes (early group) was compared with those who underwent surgery in 200 minutes or longer (late group) using univariate and multivariate analyses.A total of 161 patients were identified during the study time frame. Head computed tomographic scan demonstrated subdural hematoma in 85.8%, subarachnoid hemorrhage in 55.5%, and equal numbers of epidural hematoma and intraparenchymal hemorrhage in 22.6%. Median time between ED admission and neurosurgical intervention was 133 minutes. In univariate analysis, a significantly lower in-hospital mortality rate was identified in the early group (34.5% vs. 59.1%, p = 0.03). After adjusting for clinically important covariates in a logistic regression model, early neurosurgical intervention was significantly associated with a higher odds of patient survival (odds ratio, 7.41; 95% confidence interval, 1.66-32.98; p = 0.009).Our data suggest that the survival rate of isolated severe TBI patients who required an emergent neurosurgical intervention could be time dependent. These patients might benefit from expedited process (computed tomographic scan, neurosurgical consultation, etc.) to shorten the time to surgical intervention.Prognostic study, level IV.

In surgery patients, low preoperative serum transthyretin (TTR) level is associated with greater rates of infection and mortality. However, the predictive value of TTR on surgical outcomes after major trauma has not yet been studied.Critically ill trauma patients who underwent surgery for trauma and had TTR preoperatively measured after admission to the surgical intensive care unit (ICU) at the LAC+USC Medical Center (01/2008-05/2014) were identified retrospectively. Univariable and multivariable regression analyses determined the significance of TTR on outcomes.We identified 348 patients. Univariable analysis indicated that patients with lower TTR had more infections (P.001), higher mortality (P = .007), longer hospital stay (P.001), longer ICU stay (P.001), and increased ventilator days (P.001). Even after adjusting for differences in patient characteristics, lower TTR level was associated with greater infectious complication rates (P = .001), greater mortality (P = .005), longer hospital stay (P = .013), longer ICU stay (P = .030), and increased ventilator days (P = .044).In critically ill trauma patients, low serum TTR level is associated with poorer clinical outcomes, and its prognostic utility warrants further study.

Recent military studies demonstrated an association between prehospital tourniquet use and increased survival. The benefits of this prehospital intervention in a civilian population remain unclear. The aims of our study were to evaluate tourniquet use in the civilian population and to compare outcomes to previously published military experience. We hypothesized that incorporation of tourniquet use in the civilian population will result in an overall improvement in mortality.This is a preliminary multi-institutional retrospective analysis of prehospital tourniquet (MIA-T) use of patients admitted to nine urban Level 1 trauma centers from January 2010 to December 2013. Patient demographics and mortality from a previous military experience by Kragh et al. (Ann Surg. 2009;249:1-7) were used for comparison. Patients younger than 18 years or with nontraumatic bleeding requiring tourniquet application were excluded. Data were analyzed using a two-tailed unpaired Student's t test with p0.05 as significant.A total of 197 patients were included. Tourniquets were applied effectively in 175 (88.8%) of 197 patients. The average Injury Severity Score (ISS) for MIA-T versus military was 11 ± 12.5 versus 14 ± 10.5, respectively (p = 0.02). The overall mortality and limb amputation rates for the MIA-T group were significantly lower than previously seen in the military population at 6 (3.0%) of 197 versus 22 (11.3%) of 194 (p = 0.002) and 37 (18.8%) of 197 versus 97 (41.8%) of 232 (p = 0.0001), respectively.Our study is the largest evaluation of prehospital tourniquet use in a civilian population to date. We found that tourniquets were applied safely and effectively in the civilian population. Adaptation of this prehospital intervention may convey a survival benefit in the civilian population.Epidemiologic study, level V.

Background Increasing ambient temperature to prevent intraoperative patient hypothermia remains widely advocated despite unconvincing evidence of efficacy. Heat stress is associated with decreased cognitive and psychomotor performance across multiple tasks but remains unexamined in an operative context. We assessed the impact of increased ambient temperature on laparoscopic operative performance and surgeon cognitive stress. Study design Forty-two performance measures were obtained from 21 surgery trainees participating in the counter-balanced, within-subjects study protocol. Operative performance was evaluated with adaptations of the validated, peg-transfer, and intracorporeal knot-tying tasks from the Fundamentals of Laparoscopic Surgery program. Participants trained to proficiency before enrollment. Task performance was measured at two ambient temperatures, 19 and 26°C (66 and 79°F). Participants were randomly counterbalanced to initial hot or cold exposure before crossing over to the alternate environment. Cognitive stress was measured using the validated Surgical Task Load Index (SURG-TLX). Results No differences in performance of the peg-transfer and intracorporeal knot-tying tasks were seen across ambient conditions. Assessed via use of the six bipolar scales of the SURG-TLX, we found differences in task workload between the hot and cold conditions in the areas of physical demands (hot 10 [3–12], cold 5 [2.5–9], P = .013) and distractions (hot 8 [3.5–15.5], cold 3 [1.5–5.5], P = .001). Participant perception of distraction remained greater in the hot condition on full scoring of the SURG-TLX. Conclusion Increasing ambient temperature to levels advocated for prevention of intraoperative hypothermia does not greatly decrease technical performance in short operative tasks. Surgeons, however, do report increased perceptions of distraction and physical demand. The impact of these findings on performance and outcomes during longer operative procedures remains unclear.

Background Major trauma leads to increased nutritional requirements. However, little is known about the actual amount of calories and protein administered and the factors affecting the intake over time in critically ill trauma patients. Methods Prospective study including 100 trauma patients admitted to the Los Angeles County + University of Southern California Medical Center intensive care unit between March 2014 and October 2014. Inclusion criteria were age > 16 y, surgery at admission, and no oral nutrition. The caloric and protein intake was recorded, and requirements were calculated daily for 28 d. The nutritional intake and the impact of clinical factors on the intake over time were assessed using mixed model analysis. Results The caloric and protein intake significantly increased over time, but the median intake did not meet the median calculated requirements at any time. Multivariable analysis revealed a smaller increase of the nutritional intake over time in patients with an injury severity score > 45, whereas penetrating injury and laparotomy were associated with a higher increase of the intake. Body mass index scores ≥ 30 kg/m2, traumatic brain injury, and gastrointestinal tract injuries were associated with a smaller increase of the caloric intake over time. Conclusions The median nutritional intake did not meet the median calculated requirements over time. A smaller increase of the nutritional intake over time was found in patients with a higher injury burden, whereas penetrating injury and laparotomy were associated with a higher increase of the intake. Higher body mass index scores, traumatic brain injury, and gastrointestinal tract injuries were associated with a smaller increase of the caloric intake over time. These clinical factors can help to adjust the nutritional support in critically ill trauma patients.

The treatment of esophageal perforation (EP) remains a significant clinical challenge. While a number of investigators have previously documented efficient approaches, these were mostly single-center experiences reported prior to the introduction of newer technologies: specifically endoluminal stents. This study was designed to document contemporary practice in the diagnosis and management of EP at multiple institutions around the world and includes early clinical outcomes. A five-year (2009-2013) multicenter retrospective review of management and outcomes for patients with thoracic or abdominal esophageal perforation was conducted. Demographics, etiology, diagnostic modalities, treatments, subsequent early outcomes as well as morbidity and mortality were captured and analyzed. During the study period, 199 patients from 10 centers in the United States, Canada, and Europe were identified. Mechanisms of perforation included Boerhaave syndrome (60, 30.1%), iatrogenic injury (65, 32.6%), and penetrating trauma (25, 12.6%). Perforation was isolated to the thoracic segment alone in 124 (62.3%), with 62 (31.2%) involving the thoracoabdominal esophagus. Mean perforation length was 2.5 cm. Observation was selected as initial management in 65 (32.7%), with only two failures. Direct operative intervention was initial management in 65 patients (32.6%), while 29 (14.6%) underwent esophageal stent coverage. Compared to operative intervention, esophageal stent patients were significantly more likely to be older (61.3 vs. 48.3 years old, P < 0.001) and have sustained iatrogenic mechanisms of esophageal perforation (48.3% vs.15.4%). Secondary intervention requirement for patients with perforation was 33.7% overall (66). Complications included sepsis (56, 28.1%), pneumonia (34, 17.1%) and multi-organ failure (23, 11.6%). Overall mortality was 15.1% (30). In contemporary practice, diagnostic and management approaches to esophageal perforation vary widely. Despite the introduction of endoluminal strategies, it continues to carry a high risk of mortality, morbidity, and need for secondary intervention. A concerted multi-institutional, prospectively collected database is ideal for further investigation.

Zenker diverticulum is a rare condition commonly associated with dysphagia and respiratory symptoms/complications, which are alarming especially in the elderly population. Aim of this study was to investigate the prevalence of respiratory symptoms/complications and the effects of minimally invasive trans-oral surgery in these patients. Consecutive adult patients who underwent trans-oral septum stapling for Zenker diverticulum were included in a retrospective, observational cohort study. Pre- and postoperative symptoms, including chronic cough and aspiration pneumonia, were evaluated using a dedicated foregut questionnaire and were recorded on a prospectively maintained database. The operation was performed under general anesthesia. A barium swallow study and an upper gastrointestinal endoscopy were performed 6 months after the operation, and the foregut questionnaire was administered yearly. A total of 139 patients were finally included in the study. The median age was 72 years. In 62 (44.6%, CI 36.2–53.3) patients, there was a history of chronic cough and/or aspiration pneumonia. Chronic cough was associated with pneumonia (p

The properties of anodic passive films potentiostatically formed on polycrystalline gold in aqueous phosphate solutions were studied using voltammetry, electrochemical impedance spectroscopy, and contact angle measurements. The nature of the gold oxide layer was analyzed as a function of a potential holding in the aqueous double layer charge region at the interface between gold and the aqueous layer confined by insoluble organic solvents (hexane, chloroform, anisole, butyl acetate, xylene, and isopropyl ether). Different growth conditions change the homogeneity of the oxide layer leading to different passive properties. A synergetic effect on the gold oxidation of hydrogen dissolved in both the bulk metal and the confined aqueous layer is discussed., Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Instituto de Física de Líquidos y Sistemas Biológicos

Foregut leaks and perforations continue to account for high morbidity and mortality rates. Novel endoscopic techniques have recently changed the approach to the management of these complications. The purpose of this study was to evaluate the efficacy and safety of the Over-The-Scope Clipping system (OTSC) in a consecutive series of patients presenting with foregut leaks and perforations. We retrospectively reviewed the charts of seven consecutive patients treated between November 2010 and December 2013 in our tertiary care hospital. A parallel review of the literature was made including only patients treated with OTSC after upper gastrointestinal surgery. The median time between surgery and OTSC clipping was 18.4 days (range 7–53), and the median size of the defect was 6 mm (range 2–10). The overall OTSC success rate was 85.7 %. In 6 patients, 3 of whom had a chronic leak, the OTSC was successfully used as first-line treatment. The literature review showed that the overall success rate of the OTSC procedure was 66.7 % in esophageal defects and 80 % in gastric defects. The OTSC system is a simple and safe method for the management of postoperative foregut leaks and perforations, resulting in complete and durable closure of small (

The rising prevalence of morbid obesity has increased the demand for bariatric surgery and obesity surgery has become a sustainable treatment for morbid obesity worldwide. Sleeve gastrectomy is the most frequently performed bariatric surgical procedure for its technical simplicity and low complication rates. However, staple-line leaks at the angle of His occur in up to 3% of patients. Endoscopic placement of self-expandable metal stents is a common and effective therapeutic modality. Esophageal stricture or obstruction following stent placement is an extremely rare complication of an otherwise successful stenting procedure. We report the case of a patient with complete esophageal obstruction who required a combined endoscopic and open surgical approach for restoration of esophageal lumen and transit.

Benign submucosal esophageal tumors are rare and are most commonly represented by leiomyomas. Patients with tumors that are symptomatic or grow rapidly and require differential diagnosis with malignancy should be removed, preferably by extramucosal enucleation, through a thoracoscopic or laparoscopic approach. These minimally invasive techniques have been demonstrated to be safe and effective, and result in minimal postoperative pain, short hospital stay, and clinical outcomes equivalent to the open approach.

This paper includes commentaries on outcomes of esophageal surgery, including the mechanisms by which fundoduplication improves lower esophageal sphincter (LES) pressure; the efficacy of the Linx™ management system in improving LES function; the utility of radiologic characterization of antireflux valves following surgery; the correlation between endoscopic findings and reported symptoms following antireflux surgery; the links between laparoscopic sleeve gastrectomy and decreased LES pressure, endoscopic esophagitis, and gastroesophageal reflux disease (GERD); the less favorable outcomes following fundoduplication among obese patients; the application of bioprosthetic meshes to reinforce hiatal repair and decrease the incidence of paraesophageal hernia; the efficacy of endoluminal antireflux procedures, and the limited efficacy of revisional antireflux operations, underscoring the importance of good primary surgery and diligent work-up to prevent the necessity of revisional procedures.

Blunt pancreatic trauma is rare, and the reported mortality is high. The true outcomes in isolated pancreas trauma are not known, and the optimal management according to injury severity is controversial. The present study evaluated the incidence, outcomes, and optimal management of isolated blunt pancreatic injuries.National Trauma Data Bank study, including patients with blunt pancreatic trauma. Patients with major associated injuries or other severe intra-abdominal injuries were excluded. Patients' demographics, vital signs on admission, Abbreviated Injury Scale for each body area, Injury Severity Score (ISS), and therapeutic modality were extracted. Mortality and hospital length of stay were stratified according to the severity of pancreatic injury and therapeutic modality.There were 388,137 patients with blunt abdominal trauma. Overall, 12,112 patients (3.1%) sustained pancreatic injury. Isolated pancreatic injury occurred in 2,528 (0.7%) of all abdominal injuries or 20.9% of pancreatic injuries. Most injuries were low-grade Organ Injury Scale ((OIS) score of 2, 82.7%) with only a small percentage of higher-grade injuries (OIS score of 3, 7.9%; OIS score of 4, 3.9%; and OIS score of 5, 5.5%). Overall, most patients (74.1%) were managed nonoperatively. Nonoperative management was selected in 80.5% of pancreas OIS score of 2, 48.5% of OIS score of 3, and 40.9% of OIS scores of 4 to 5. The overall mortality rate was 2.4%, while in severe pancreatic trauma it was 3.0%. In minor pancreatic trauma, nonoperative management was associated with lower mortality and shorter hospital length of stay than operative management. However, in the group of patients with severe pancreatic trauma (OIS scores, 4-5) nonoperative management was associated with higher mortality and longer hospital stay than definitive operative management of the pancreas.The mortality in isolated pancreatic trauma is low, even in severe injuries. Nonoperative management of minor pancreatic injuries is associated with lower mortality and shorter hospital stay than operative management. However, in severe trauma, nonoperative management is associated with higher mortality and longer hospital stay than operative management.Prognostic study, level III; therapeutic study, level IV.

Background Severe muscle mass depletion, sarcopenia, has been shown to be associated with poor operative outcomes. However, its impact on emergency abdominal operations remains unclear. The purpose of this study was to examine the association between low muscle mass (LMM) and outcomes after emergency operations for acute diverticulitis. Patients and methods Patients ≥18 y requiring an emergency operation for acute diverticulitis between January 2007 and September 2014 were included. On preoperative computed tomography, the cross-sectional area (CSA) and transverse diameter (TVD) of the right and left psoas muscle were measured at the level of the third lumbar vertebral body. Sensitivity analysis was performed to determine appropriate CSA and TVD cutoff values defining low skeletal muscle mass. Clinical outcomes of patients with low muscle mass (LMM group) were compared with the non-LMM group. Results A total of 89 patients met our inclusion criteria. Median CSA and TVD were 794 mm 2 and 24 mm, respectively. There was a strong correlation between the CSA and TVD (R 2 = 0.84). In univariable analysis, significantly higher rates of postoperative major complications (63% versus 37%, P = 0.027) and surgical site infection (47% versus 19%, P = 0.008) were identified in the LMM group. After adjusting for clinically important covariates in a logistic regression model, patients with LMM were significantly associated with higher odds of major complications and surgical site infection. Conclusions Preoperative assessment of the psoas muscle CSA and TVD on computed tomography can be a practical method for identifying patients at risk for postoperative complications.

The aim of this study was to identify patients' characteristics that may predict failure and removal of the Linx sphincter augmentation device, and to report the results of 1-stage laparoscopic removal and fundoplication.The Linx device is a long-term magnetic implant that was developed as a less disruptive and more reproducible surgical option for patients with early-stage gastroesophageal reflux disease (GERD). Removal of the device has been shown to be feasible, but no long-term results of this procedure have been reported yet.A review of the prospectively collected research database of antireflux surgery was performed to identify all patients who underwent a Linx implant between 2007 and 2015 in our Institution. Demographics, duration of symptoms and proton pump inhibitor (PPI) therapy, GERD-Health Related Quality of Life scores, esophageal acid exposure, lower esophageal sphincter pressure, number of beads (size) of the implanted device, concurrent crura repair, angle of inclination of the device at postoperative chest film, operative time, postoperative complications, and length of stay were recorded. Data of the explanted patients were compared with those with the device in situ in an attempt to identify factors associated with Linx removal.Over the study period, 164 patients underwent a laparoscopic Linx implant and had a median follow-up of 48 months [interquartile range (IQR) 36]. Eleven (6.7%) of these patients were explanted at a later date. The estimated removal-free probability at 80 months was 0.91 [confidence interval (CI) 0.86-0.96]. Supine esophageal acid exposure before the index operation was associated with Linx removal (odds ratio 1.05, CI 1.01-1.11, P = 0.037). The main presenting symptom requiring device removal was recurrence of heartburn or regurgitation in 5 patients (46%), followed by dysphagia (n = 4, 37%) and chest pain (n = 2, 18%). In 2 patients, full-thickness erosion of the esophageal wall with partial endoluminal penetration of the device occurred. The median implant duration was 20 months, with 82% of the patients being explanted between 12 and 24 months after the implant. Device removal was most commonly combined with partial fundoplication. There were no conversions to laparotomy and the postoperative course was uneventful in all patients. At the latest follow-up, ranging from 12 to 58 months, the GERD-HRQL score was within normal limits in all patients.Laparoscopic removal of the Linx device can be safely performed as a 1-stage procedure and in conjunction with fundoplication even in patients presenting with device erosion.

Despite significant advances in diagnosis and treatment, esophageal perforation remains a life-threatening event and an emergency condition particularly challenging for the surgeon. Iatrogenic injury is the most frequent cause of esophageal perforation, accounting for 59 % of all patients, followed by spontaneous rupture (15 %), foreign body ingestion (12 %), trauma (9 %), and esophageal cancer (1 %) [1].

A general numerical algorithm is proposed for the fast computation of the common volume function (CVF) of any polyhedral object, from which the diffraction pattern of a corresponding powder can be obtained. The theoretical description of the algorithm is supported by examples ranging from simple equilibrium shapes in cubic materials (Wulff polyhedra) to more exotic non-convex shapes, such as tripods or hollow cubes. Excellent agreement is shown between patterns simulated using the CVF and the corresponding ones calculated from the atomic positionsviathe Debye scattering equation.

Paper is an organic material widely used in cultural heritage and mainly composed of cellulose mixed with lignin, hemicellulose and small amounts of additives. This paper deals with siloxane coatings on pure cellulose paper, applied by sol–gel dipping in sols prepared with different siloxane precursors (tetraethoxysilane, methyl triethoxysilane, dimethyl diethoxysilane, trimethyl monoethoxysilane). The coated samples were characterized using various techniques (Fourier Transform Infrared Spectroscopy FT-IR, Nuclear Magnetic Resonance NMR and Scanning Electron Microscopy and Energy Dispersive Spectroscopy SEM–EDS), measuring their mechanical properties, flame resistance and contact angles, and a colorimetric test. The coated samples’ behavior was more hydrophobic the higher the methyl number of siloxane precursor, regardless of the coating’s thickness. Increasing the thickness improved the mechanical and thermal properties. The thickest coatings were obtained using a double coating process and a basic catalyst for the hydrolysis step, but this latter condition facilitated the formation of surface agglomerates, which make the paper too stiff and yellow.

Background The American Association for the Surgery of Trauma (AAST) has developed a new grading system for uniform description of anatomic severity of emergency general surgery (EGS) diseases, ranging from Grade I (mild) to Grade V (severe). The purpose of this study was to determine the relationship of AAST grades for acute colonic diverticulitis with patient outcomes. A secondary purpose was to propose an EGS quality improvement program using risk-adjusted center outcomes, similar to National Surgical Quality Improvement Program and Trauma Quality Improvement Program methodologies. Methods This was a retrospective study of 1,105 patients (one death) from 13 centers. At each center, two reviewers (blinded to each other's assignments) assigned AAST grades. Interrater reliability was measured using κ coefficient. Relationship between AAST grade and clinical events (complications, intensive care unit use, surgical intervention, and 30-day readmission) as well as length of stay was measured using regression analyses to control for age, comorbidities, and physiologic status at the time of admission. Final model was also used to calculate observed-to-expected (O-E) ratios for adverse outcomes (death, complications, readmissions) for each center. Results Median age was 54 years, 52% were males, 43% were minorities, and 22% required a surgical intervention. Almost two thirds had Grade I or II disease. There was a high level of agreement for grades between reviewers (κ = 0.81). Adverse events increased from 13% for Grade I, to 18% for Grade II, 28% for Grade III, 44% for Grade IV, and 50% for Grade V. Regression analysis showed that higher disease grades were independently associated with all clinical events and length of stay, after adjusting for age, comorbidities, and physiology. O-E ratios showed statistically insignificant variations in risk of death, complications, or readmissions. Conclusion AAST grades for acute colonic diverticulitis are independently associated with clinical outcomes and resource use. EGS quality improvement program methodology that incorporates AAST grade, age, comorbidities, and physiologic status may be used for measuring quality of EGS care. High-quality EGS registries are essential for developing meaningful quality metrics. Level of evidence Prognostic study, level V.

In this work a new simple method to improve the bulk properties of paper is presented. Co-polymerization of vinyl functionalised zirconia oxoclusters with vinyl trimethoxysilane was carried out onto paper. The coating process was evaluated also taking into account the specific weight of hybrid polymer left on the paper after one or two deposition steps, and with or without a thermal treatment of curing. The effectiveness of the coating process in consolidating and protecting paper was investigated by measurements with High Temperature Differential Scanning Calorimetry, Dynamical Mechanical Spectroscopy, tensile testing, contact angle, along with Environmental Scanning Electron Microscopy. The coating process does not affect the morphology and appearance of the paper, but modifies its mechanical, surface and thermal properties.

The familiar Young contact angle measurement of a liquid at equilibrium on a solid is a fundamental aspect of capillary phenomena. But in the real world it is not so easy to observe it. This is due to the roughness and/or heterogeneity of real surfaces, which typically are not perfectly planar and chemically homogeneous. What can be easily detected, and in a repeatable way, are advancing and receding contact angles. In this paper, we discuss a simple model which accounts for the onset of advancing and receding contact angles measured by the Wilhelmy microbalance, one of the most powerful techniques for contact angle measurements. The model also explains the experimental observation that advancing and receding contact angles become closer to each other when the system is gently 'shaken', by supplying mechanical energy in an appropriate way. The model may be pedagogically useful in introducing students and teachers to aspects of capillary phenomena which are not usually discussed in basic physics courses.

The present generation of mechanical heart-valves prostheses offers significantly improved blood compatibility, combined with appropriate physical and mechanical properties and durability; however, thromboembolism persists as a crucial clinical complication because of the key role played by adsorbed plasma proteins and adherent platelets in determining hemocompatibility. In the present work human plasma protein adsorption and platelet adhesion and activation were evaluated on four materials, selected according to their different physico-chemical and morphological properties: pyrolytic carbon (PyC), titanium alloy Ti–6Al–4V (Ti), tissue culture polystyrene (TCPS) and polystyrene sterilized by γ-irradiation (StPS). Morphological and chemical properties of surfaces were assessed by Time of Flight Secondary Ion Mass Spectrometry (Tof-SIMS), X-ray Photoemission Spectroscopy (XPS), Atomic Force Microscopy (AFM) and Contact Angle (CA) analysis, while protein adsorption and platelet adhesion and activation were evaluated by colorimetric and immunofluorescence tests and Scanning Electron Microscopy (SEM), respectively. Among the analyzed materials, PyC induced the lowest level of protein adsorption and platelet adhesion and activation. In particular, immunofluorescence analysis of fibronectin (FN), fibrinogen (FG), von Willebrand factor (vWF), Hageman factor (FXII) and albumin (ALB) showed that PyC surface was characterized by high levels of FG adsorption, low levels of FN, ALB and vWF and the absence of FXII. Finally, when analyzing the biological response as a function of surface properties, it was found that protein adhesiveness increased with increasing contact angle values. To the contrary, platelet activation related to the total amount of adherent proteins was poor while cell activation was possibly dependent on the detailed composition of the underlying protein layer. Furthermore, differences in surface roughness of the examined materials did not seem to influence the biological response in terms of platelet activation and protein adsorption.

Description Flexible endoscopic treatment of Zenker's diverticulum is feasible, but electrocautery and CO2 laser technology carry the risk of collateral thermal injury. Thulium laser septum incision may overcome this limitation. We describe for the first time the use of thulium laser through flexible endoscopy in a small cohort of patients with Zenker diverticulum. Methods Thulium laser septum division was performed via flexible endoscopy under general anesthesia in 11 consecutive symptomatic patients with primary or recurrent Zenker diverticulum. Primary study aims were feasibility and safety of the procedure. To improve exposure and stabilize the septum during the procedure, either a transparent cap or a bivalve soft overtube were used. The laser system used was Opera® (Quanta System SpA, Varese, Italy), emitting a 1.9 μm Thulium wavelength radiation. A continuous laser configuration and an emission power of 5 to 16 W were chosen to allow incision of the mucosa and cricopharyngeal myotomy. Using 272 and 365 μm optical fibres in a non-contact mode, laser incision was performed in the midline of the septum until cricopharyngeal muscle fibers were encountered and a V-shaped myotomy was completed under visual control. Results Between May and January 2018, 11 consecutive patients were treated. Four patients presented with recurrent symptomatic diverticulum after previous transoral septum stapling or endoscopic myotomy. Median dysphagia and regurgitation scores were 4.1 ± 0.7 and 3.3 ± 0.8 respectively. Complete division of the septum was achieved in all patients. There was no bleeding nor need of adjunctive electrocautery devices to complete the procedure. The post-operative course was uneventful in all patients; the chest film and gastrographin swallow study on post-operative day one were negative for pneumomediastinum or leaks. All patients were discharged within 48 hours on a soft diet. At the 2-month follow-up visit, all patients were satisfied with the procedure with a post-operative dysphagia score of 2.0 ± 0.6 and a regurgitation score of 1.5 ± 0.4. Conclusions Division of Zenker's septum with Thulium laser is feasible and safe through flexible endoscopy. Longer term follow-up is required to establish effectiveness and reproducibility of this novel procedure. Disclosure All authors have declared no conflicts of interest.

Background Minimally invasive enucleation of esophageal leiomyoma may induce or aggravate gastroesophageal reflux disease, but scarce data are available in literature. Methods We conducted a retrospective, cross-sectional single-center study investigating long-term outcomes of laparoscopic, thoracoscopic, and endoscopic enucleation with focus on quality of life and gastroesophageal reflux. Postoperative clinical and endoscopic data were compared to baseline. All patients underwent barium swallow study, endoscopy and completed the GERD-HRQL questionnaire after a minimum 1-year follow-up. Results Thirty patients were included in the study. There were 19 females and 11 males, median age 48 years (range 28–67). Thirteen (43.3%) patients underwent laparoscopic enucleation plus fundoplication (9 Toupet, 3 Nissen, 1 Dor), 12 (40%) patients thoracoscopic enucleation, and 5 (16.7%) patients endoscopic enucleation. Mean operative time was 149.1 ± 62.6 min. Mean tumor diameter was 5.4 ± 3.2 cm. There was no operative mortality. Overall morbidity rate was 16.6%, and no mucosal perforations occurred. Mean hospital stay was 4.0 ± 1.8 days. The mean baseline GERD-HRQL score was 4.25 (range 0–21) in the laparoscopic group, 3.4 (range 0–12) in the thoracoscopic group, and 5.7 (range 0–13) in the endoscopic group. Preoperatively, hiatal hernia was present in 6 patients (46.1%) in the laparoscopic group, in 4 patients (33.3%) in the thoracoscopic group, and in 2 patients (40%) in the endoscopic group. The mean follow-up was 58 months (range 3–192) (Table 1). Conclusion GERD symptoms were more common in patients after endoscopic enucleation. Primary laparoscopic enucleation combined with fundoplication allows effective long-term reflux control. Disclosure All authors have declared no conflicts of interest.

The magnetic sphincter augmentation (MSA) procedure is a highly standardized laparoscopic surgical option for patients with well-documented gastroesophageal reflux disease who do not fully respond to medical treatment with proton-pump inhibitors (PPIs), complain of volume regurgitation, or develop progressive/refractory symptoms despite escalation therapy. The effectiveness of the MSA procedure has been proven in patients with typical reflux symptoms and PPI dependent who show an increased esophageal acid exposure on prolonged pH monitoring. Observational studies have demonstrated that MSA compares well with Nissen and Toupet laparoscopic fundoplication (LF) in selected patients, and has an acceptable risk profile. Whenever necessary, the MSA device can be explanted via laparoscopy without complications or long-term consequences, and a standard fundoplication can be concomitantly performed. Combining formal crural repair with MSA appears to strengthen the antireflux effect and reduce the need of reoperation. MSA represents a reasonable therapeutic option in patients with gastroesophageal reflux disease (GERD) and perhaps an alternative to LF.

With the development of tissue banking, a need for homogeneous methods of collection, processing, and storage of tissue has emerged. We describe the implementation of a biological bank in a high-volume, tertiary care University referral center for esophageal cancer surgery. We also propose an original punch biopsy technique of the surgical specimen. The method proved to be simple, reproducible, and not expensive. Unified standards for specimen collection are necessary to improve results of specimen-based diagnostic testing and research in surgical oncology.

Woven and nonwoven fabrics and the corresponding fibers have been analyzed using a Wilhelmy microbalance. A self-developed analysis software (written using Labview flow-data language) has been used to extract the advancing and receding angles and also other informations commonly neglected by the standard data analysis of Wilhelmy technique, such as the immersion cross-sectional area, the effective wet perimeter, the liquid absorption, the parallelism of the straight lines describing the immersion and the withdrawal of the sample in a typical force vs immersion graph. This approach has previously been proposed for rigid porous materials such as stones and wood with some success. In the present cases some modifications of the approach have been introduced to take into account the specificity of the materials. The results appear promising for the more rigid nonwoven fabric, but suffer from a greater uncertainty and from even unacceptable inconsistencies in the case of the softer and traditional fabric. Throu...

Axisymmetric drop shape analysis (ADSA) is a well-established methodology for estimating the contact angle value and the surface tension of liquids starting from sessile drops images. It consists of an iterative procedure in which a best fit between a theoretical axisymmetric Laplacian curve and an experimental drop profile is performed. When only an evaluation of the geometric contact angle value is needed, a similar numerical approach can be adopted by using simpler algebraic models in place of a Laplace profile, thus allowing more straightforward implementations and shorter computation times. In this work the relative merits of the different methodologies are compared. Beside the standard ADSA procedure, four different mathematical models are examined, namely the circular and elliptical models, the first-order perturbative solution of the Laplace equation, and a cubic spline model. Their relative statistical performances are tested on both calculated and experimental drop profiles. For simulated drops, the actual capability of the models to predict the correct contact angle is also investigated.

A simple variational property concerning the velocity distribution of a set of point particles is illustrated. This property provides a full characterization of the velocity distribution which minimizes the kinetic energy of the system for prescribed values of linear and angular momentum. Such a characterization is applied to discuss the kinetic energy dissipation in the sticking collision of free rigid bodies. Special cases are also examined where not all the components of linear and angular momentum are conserved, corresponding to rigid bodies with a common fixed point or axis without friction. As a byproduct, a formal property of the tensor of inertia is derived, not commonly considered in mechanics textbooks. Along with the variational property of the velocity distribution, such a formal property of the tensor of inertia may be interesting for graduate and advanced undergraduate students.

The same underlying mathematical structure characterizes some of the most popular multicomponent models for the prediction of surface free energies and adhesion works. After a brief illustration of the general methods for the computation of liquid and solid components in typical multicomponent theories, it is shown that both model definition and component estimate may take great advantage from application of Principal Component Analysis techniques, owing to the very peculiar structure of adhesion work equations. It is also put into evidence that a problem of scale multiplicity arises as a consequence of the symmetries involved in the model equations for adhesion work and surface free energy. A special discussion is devoted to the specific cases of van Oss–Chaudhury–Good acid–base theory, Qin–Chang model and extended Drago theory, which constitute the most common multicomponent models usually applied in the analysis of adhesion phenomena.

The environmental scanning electron microscope (ESEM) represents one of the most exciting breakthroughs in electron microscopy since the invention of the electron microscope. Its ability to observe uncoated and hydrated samples enhances the possibility for investigating the wettability of surfaces at a microscopic level; by varying the relative vapour pressure or the temperature inside the chamber, it is possible to condense water drops on a micron scale. A large problem in measuring contact angles by ESEM is that the observation angle is not parallel or perpendicular to the surface; thus, the study of the droplets profile using the common algorithms such as spherical approximation or axisymmetric drop shape analysis (ADSA) is not possible, because only a spherical cap shape is commonly observed. In this paper we provide a useful mathematical model to calculate the real contact angle from the initial images. Initially, some simulated spherical caps with different contact and observation angles were created by an appropriate graphic package in order to test the mathematical model. Some real drops obtained by ESEM on wax and polymethylmethacrylate (PMMA) were then studied and the results compared with contact angles measured by common methods on the same materials.

Background Deep organ space infection (DOSI) is a serious complication after emergency bowel resection and anastomosis. The aim of this study was to identify the incidence and risk factors for the development of DOSI. Methods National Surgical Quality Improvement Program database study including patients who underwent large bowel or small bowel resection and primary anastomosis. The incidence, outcomes, and risk factors for DOSI were evaluated using univariate and multivariate analyses. Results A total of 87,562 patients underwent small bowel, large bowel, or rectal resection and anastomosis. Of these, 14,942 (17.1%) underwent emergency operations and formed the study population. The overall mortality rate in emergency operations was 12.5%, and the rate of DOSI was 5.6%. A total of 18.0% required ventilatory support in more than 48 hours, and 16.0% required reoperation. Predictors of DOSI included age, steroid use, sepsis or septic shock on admission, severe wound contamination, and advanced American Society of Anesthesiologists classification. The anatomic location of resection and anastomosis was not significantly associated with DOSI. Conclusion Patients undergoing emergency bowel resection and anastomosis have a high mortality, risk of DOSI, and systemic complications. Independent predictors of DOSI include wound and American Society of Anesthesiologists classification, sepsis or septic shock on admission, and steroid use. The anatomic location of resection and anastomosis was not significantly associated with DOSI. Level of evidence Epidemiologic/prognostic study, level III.

BACKGROUND The ideal prehospital management of patients with severe traumatic brain injury (TBI) including the impact of endotracheal intubation (ETI) and physicians on scene is unclear. Prehospital management differs substantially in Switzerland and the United States: in Switzerland, there is usually a physician on scene who may provide ETI and other advanced life support procedures, whereas in the United States, prehospital management (including ETI) is performed by paramedics. METHODS This is a retrospective cohort-matched study of patients with isolated blunt severe TBI (head Abbreviated Injury Scale [AIS] score, 4-5) and no major extracranial injuries, using Bern University Hospital data from the Swiss PEBITA [Patient-relevant Endpoints after Brain Injury from Traumatic Accidents] (TBI-specific) database and the US National Trauma Data Bank from 2009 to 2010. A 1:4 cohort matching of Bern and US patients was performed. Matching criteria were sex, age (±10 years), exact field Glasgow Coma Scale (GCS) score, exact head AIS score, and injury type (subdural hematoma, epidural hematoma, intraparenchymal hemorrhage, intraventricular hemorrhage, brain edema/swelling, brain stem injury). The matched cohorts were compared with univariable analysis (Fisher's exact test and Mann-Whitney U-test). RESULTS Matching of the Bern (n = 128) and US (n = 86,375) cohort resulted in 355 matched cases (71 Bern and 284 US patients). Bern patients had significantly longer scene times (median, 23.0 minutes vs. 9.0 minutes, p < 0.001) and more frequent prehospital ETI (31.0% vs. 18.7%, p = 0.034) and air transportation (39.4% vs. 19.4%, p < 0.001). No significant difference in procedures (craniotomy/craniectomy, intracranial pressure monitoring, tracheotomy), intensive care unit and total hospital lengths of stay, ventilator days, and in-hospital mortality (14.1% vs. 15.8%, p = 0.855) was found between the two cohorts. CONCLUSION When taking into account the limitation that patient- and injury-related factors, but not in-hospital treatment variables, were matched, the more frequent prehospital ETI and presence of a physician on scene in the Swiss cohort compared with the US cohort had no significant effect on outcomes, including intensive care unit and total hospital lengths of stay, ventilator days, and in-hospital mortality. LEVEL OF EVIDENCE Therapeutic study, level IV.

Background Unlike in the military setting, where the use of tourniquets has been well established, in the civilian sector their use has been far less uniform. The purpose of this study was to examine the outcomes associated with the use of tourniquets for civilian extremity trauma. Study design Adult (≥18 years) patients admitted to our institution with an extremity injury requiring tourniquet application from January 2007 to June 2014 were retrospectively reviewed. The primary outcome analyzed was limb loss. Secondary outcomes included death, hospital length of stay, and complications. Results There were 87 patients who met inclusion criteria. Average age was 35.3 years, 90.8% were male, and 66.7% had penetrating injuries, with a median Injury Severity Score (ISS) of 6. Tourniquets were placed in the prehospital setting in 50.6%, in the emergency department in 39.1%, and in the operating room in 10.3% of patients. The windlass type Combat Application Tourniquet was the most commonly used type (67.8%), followed by a pneumatic system (24.1%) and self-made tourniquet (8.0%). The median duration of use was 75 minutes (interquartile range, 91) with no differences between groups (p = 0.547). Overall, 80.5% had a vascular injury (70.1% arterial), and a total of 99 limb operations were performed, including 15 amputations. Fourteen amputations (93.3%) occurred at the scene or were directly attributed to the extent of tissue damage with a median Mangled Extremity Severity Score (MESS) of 7 (interquartile range, 2). In the remaining patient, the tourniquet was lifesaving but likely contributed to limb loss. Seven patients sustained 13 other complications; however, none was directly attributed to tourniquet use. Conclusion Tourniquet use in the civilian sector is associated with a low rate of complications. With the low complication rate and high potential for benefit, aggressive use of this potentially lifesaving intervention is justified. Level of evidence Epidemiologic/prognostic study, level III.

The practice of transfusing ones' own shed whole blood has obvious benefits such as reducing the need for allogeneic transfusions and decreasing the need for other fluids that are typically used for resuscitation in trauma. It is not widely adopted in the trauma setting because of the concern of worsening coagulopathy and the inflammatory process. The aim of this study was to assess outcomes in trauma patients receiving whole blood autotransfusion (AT) from hemothorax.This is a multi-institutional retrospective study of all trauma patients who received autologous whole blood transfusion from hemothorax from two Level I trauma centers. Patients who received AT were matched to patients who did not receive AT (No-AT) using propensity score matching in a 1:1 ratio for admission age, sex, mechanism, type of injury, Injury Severity Score (ISS), Glasgow Coma Scale (GCS) score, systolic blood pressure, heart rate, hemoglobin, international normalized ratio (INR), prothrombin time, partial prothrombin time, and lactate. AT was defined as transfusion of autologous blood from patient's hemothorax, which was collected from the chest tubes and anticoagulated with citrate phosphorous dextrose. Outcome measures were in-hospital complications, 24-hour INR, and mortality. In-hospital complications were defined as adult respiratory distress syndrome, sepsis, disseminated intravascular coagulation, renal insufficiency, and transfusion-related acute lung injury.A total of 272 patients (AT, 136; No-AT, 136) were included. There was no difference in admission age (p = 0.6), ISS (p = 0.56), head Abbreviated Injury Scale (AIS) score (p = 0.42), systolic blood pressure (p = 0.88), and INR (p = 0.62) between the two groups. There was no significant difference in in-hospital complications (p = 0.61), mortality (p = 0.51), and 24-hour postadmission INR (0.31) between the AT and No-AT groups. Patients who received AT had significantly lower packed red blood cell (p = 0.01) and platelet requirements (p = 0.01). Cost of transfusions (p = 0.01) was significantly lower in the AT group compared with the No-AT group.The autologous transfusion of the patient's shed blood collected through chest tubes for hemothorax was found to be safe without complications in this study. It also reduced the need for allogeneic transfusions and decreased hospital costs. This study demonstrates safety data that would help in designing larger prospective multicenter studies to determine whether this practice is truly safe and effective.Epidemiologic/prognostic study, level III.

In the topological approach to structure-property relationships, the molecular structure is described in terms of appropriate weighted graphs to which suitable topological parameters, usually known as molecular connectivity indices, can be associated. Molecular connectivity indices are here applied to the prediction of surface free energy and Good-van Oss-Chaudhury acid-base components of organic compounds. To this aim, some quantitative structure-property relationships (QSPRs) are determined, involving both topological indices and group indicator variables of the customary functional group theory. The semiempirical models obtained to appear satisfactory and show significant advantages with respect to the models based on the purely functional group approach.

The advancing angle is the commonest way to measure and use the contact angle. Sometimes its use is an acceptable approximation, whereas in other cases it is simply not useful or misleading. This is the case of a natural porous material, such as stone. The stone materials are heterogeneous and rough, and the application of protective agents makes their surfaces even more complex. This paper confirms that the measurement of the advancing angles can only indicate the presence of the protective, not its effective protecting ability. On the contrary, the receding angles correlate better with the chemical structure and protective ability of the protecting agents (e.g. with the water absorption). Some examples of evaluations of commercial and newly synthesised protective polymers show the advantages and limitations of the use of the contact angles and the difficulties of their interpretation. Moreover, new and originally chosen protective agents, i.e. some cationic surfactants already used as “rinsing aids” and polyvynilpyrrolidone waxes, have been tested as protective with interesting results. The time dependence of protection efficacy and its correlation with contact angle have also been tested.

The acid-base approach to the calculation of solid surface free energy and liquid-liquid interfacial tensions is a practical example of application of correlation analysis, and thus it is an approximate approach. In these limits, and provided that wide and well-obtained sets of contact angles or interfacial tension data are used for their computation, surface tension components can be considered as material properties. Although their numerical value depends on the characteristics of the chosen reference material, their chemical meaning is independent on the selected scale. Contact angles contain accessible information about intermolecular forces; using surface tension component (STC) acid-base theory, one can extract this information only making very careful use of the mathematical apparatus of correlation analysis. The specific mathematical methods used to obtain these results are illustrated by using as an example a base of data obtained by the supporters of the equation-of-state theory (EQS). The achievements are appreciably good and the agreement between STC and EQS is discussed.