Second Data Release from the European Pulsar Timing Array: Challenging the Ultralight Dark Matter Paradigm.

Pulsar Timing Array experiments probe the presence of possible scalar or pseudoscalar ultralight dark matter particles through decade-long timing of an ensemble of galactic millisecond radio pulsars. With the second data release of the European Pulsar Timing Array, we focus on the most robust scenario, in which dark matter interacts only gravitationally with ordinary baryonic matter. Our results show that ultralight particles with masses 10^{-24.0} eV≲m≲10^{-23.3} eV cannot constitute 100% of the measured local dark matter density, but can have at most local density ρ≲0.3 GeV/cm^{3}.

One-shot platelet-rich plasma (PRP) injection is non-inferior to extracorporeal shockwave therapy in the management of supraspinatus tendinosis.

PURPOSE: Supraspinatus tendinosis (ST) refers to the intratendinous degeneration of the supraspinatus tendon. Platelet-Rich Plasma (PRP) is one of the possible conservative treatments for supraspinatus tendinosis. This prospective observational study aims to evaluate the efficacy and safety of a single ultrasound-guided PRP injection in the treatment of supraspinatus tendinosis and to assess its non-inferiority to the widely used shockwave therapy. METHODS: Seventy-two amateur athletes (35 male, mean age: 43.75 ± 10.82, range 21-58 years old) with ST were finally included in the study. All the patients underwent clinical evaluation at baseline, (T0) and at 1-month (T1), 3-month (T2) and 6-month (T3) follow-up using the following clinical scales: the Visual Analogue Scale for pain (VAS), Constant Score and the Disabilities of the Arm, Shoulder and Hand Score (DASH). A T0 and T3 ultrasound examination was also performed. The findings observed in the recruited patients were compared to the clinical results observed in a retrospective control group made up of 70 patients (32 male, mean age = 41.29 ± 13.85, range 20-65 years old) treated by extracorporeal shockwave therapy (ESWT). RESULTS: VAS, DASH and Constant scores significantly improved from T0 to T1; the improvement in clinical scores was kept until T3. No local nor systemic adverse events were observed. An improvement in the tendon structure was observed on ultrasound examination. PRP showed a non-statistical inferiority, in terms of efficacy and safety, compared to ESWT. CONCLUSION: The PRP one-shot injection is a valid conservative treatment to reduce pain, and improve both quality of life and functional scores in patients with supraspinatus tendinosis. Furthermore, the PRP intratendinous one-shot injection showed a non-inferiority in terms of efficacy at the 6-month follow-up, compared to ESWT.

The longitudinal outcome of canine (K9) myxomatous mitral valve disease (LOOK-Mitral) registry: Baseline treatment characteristics.

OBJECTIVES: To describe the medical treatment prescribed or modified by veterinary cardiologists at the enrollment visit in dogs included in the longitudinal outcome of canine (K9) myxomatous mitral valve disease (MMVD) registry (LOOK-mitral registry) and to evaluate the influence of the EPIC trial and other selected variables on cardiologist prescription habits. ANIMALS: The medical records of 6,102 dogs enrolled in the LOOK_mitral registry between 2015 and 2018 were retrospectively reviewed and 6,016 dogs were included. RESULTS: A medical treatment was prescribed by a cardiologist to 2,599 dogs (15% Stage-B1, 90% Stage-B2 and to all dogs in Stage-C). Angiotensin converting enzyme inhibitors (Ace-i) were the treatment most commonly prescribed for dogs in Stage-B1 (n = 352, 9%). The combination of pimobendan and an Ace-i was the most common treatment in Stage-B2 dogs (n = 367, 41%). Furosemide, an Ace-i, and pimobendan was the most common cardiac medical treatment prescribed for ACVIM Stage-C dogs (n = 704, 57%). Within each stage, dogs with larger left atrial and left ventricular dimensions were more likely to receive Ace-i, pimobendan or spironolactone. There was a four-fold increase in pimobendan prescription in Stage-B2 dogs after the publication of the EPIC trial. Moreover, a 15% reduction in Ace-i prescription and a 30% reduction in spironolactone prescription occurred after EPIC. In 974 dogs, a medical treatment was prescribed by the referring veterinarian. This was not changed (12%), modified (74%), or discontinued (14%) by the cardiologist. CONCLUSIONS: The EPIC trial and the echocardiographic assessment of left atrial and ventricular dimensions influence cardiologists' prescription habits.

The Longitudinal Outcome Of Canine (K9) myxomatous mitral valve disease (LOOK-Mitral registry): Baseline characteristics.

INTRODUCTION: The Longitudinal Outcome Of Canine (K9) myxomatous mitral valve disease (MMVD) registry (LOOK-Mitral registry) was established to describe the natural history and predictors of outcome in dogs affected by MMVD. This study was intended to describe the baseline characteristics of dogs in the LOOK-mitral registry. ANIMALS: Dogs with echocardiographic evidence of MMVD were prospectively enrolled by thirteen referral centers. RESULTS: A total of 6102 dogs with MMVD were included. The median age was 10 years (1-19 years), and mixed breed was the most common breed (n = 1,360, 22%). Concomitant diseases were reported in 2459 dogs with chronic respiratory diseases occurring most frequently (14%), followed by the presence of azotemia (6%) and orthopedic diseases (5%). Regarding disease severity, 65% of dogs were in ACVIM Stage-B1, 15% in Stage-B2, and 20% in Stage-C. Dogs in Stage-B1 were younger (p<0.001) than dogs in other stages. Murmur intensity, heart rate during physical examination, and radiographic vertebral heart score were positively associated with the stage. Dogs in Stage-C were more likely to have tachypnea (p<0.001), dyspnea (p<0.001), cough (p<0.001), syncopal episodes (p<0.001), and tachyarrhythmias (p<0.001) compared to dogs in Stage-B1 and B2. Echocardiographic indices of left atrial and ventricular size were positively correlated with the ACVIM stage. Interestingly, 4% of dogs that weighed <20 kg had an increased normalized end-systolic left ventricle internal diameter (>1.26). CONCLUSIONS: This study contributes to a better understanding of the clinical characteristics of dogs affected by MMVD and provides new findings that may be of clinical relevance.

Predictors of reoccurrence of congestive signs within 180 days after successful treatment of the first episode of congestive heart failure in dogs with myxomatous mitral valve disease.

INTRODUCTION: Myxomatous mitral valve disease (MMVD) is the most common cause of left-sided congestive heart failure in dogs. We sought to identify predictors of first reoccurrence of congestive signs (CS) within 180 days in dogs with MMVD and clinically stable heart failure. ANIMALS: A total of 445 dogs affected by stable American College of Veterinary Internal Medicine (ACVIM)-Stage-C MMVD were included, 106 in the reoccurrence group (RG) and 339 in no reoccurrence group (NRG). Patients were considered "stable" if medical treatment had been unchanged for at least 4 weeks since the first identification of CS. METHODS: Medical records of dogs with stable ACVIM-Stage-C MMVD included in a registry of dogs affected by MMVD were reviewed. Follow-up was required for inclusion in this investigation. Logistic regression was used to identify clinical and echocardiographic variables that independently predict first reoccurrence of CS. RESULTS: Baseline left atrial-aortic ratio (p=0.022, OR: 1.89, 90% CI: 1.20-2.98), left ventricular internal diameter at end-diastole (LVIDd_N) (p=0.014, OR: 2.84, 90% CI: 1.41-5.77), peak velocity of early diastolic transmitral flow (p=0.049, OR: 1.81, 90% CI: 1.10-3.00) and furosemide daily dosage (p=0.039, OR: 1.19, 90% CI: 1.04-1.37) were associated with reoccurrence of CS in univariable analyses. The LVIDd_N (p=0.014) remained significant in the multivariable analysis, but the area under the receiver operator characteristic curve was 0.57. CONCLUSION: This study failed to identify accurate predictors of reoccurrence of CS. However, dogs with larger value of LVIDd_N are more likely to have reoccurrence of CS within 180 days.

Humeral shaft butterfly fractures managed with intramedullary nail: could the third fragment features predict the fracture healing time?

To assess the impact of the radiological features of the third fragment on the outcome of humeral shaft fractures type 12-B managed with endomedullary nails. We retrospectively evaluated a series of 80 patients, divided into 3 groups, according to the fracture healing time: within 6 months (group-A), between 6 and 12 months (group-B) or fracture non-union after 12 months (group-C). In 26 patients out of 80 the fracture healing was observed at 6 months follow-up; in 47 out of 80 at 12 months after trauma and in 7 out of 80 no fracture healing was observed at 12 months follow-up. Regression analysis showed that the third fragment displacement and angulation are the most important features that affect the fracture healing. The mean third fragment dislocation (cut-off: 12 mm) is the main parameter to influence the fracture healing within or in more than six months.

Methods for estimating complier average causal effects for cost-effectiveness analysis.

In randomized controlled trials with treatment non-compliance, instrumental variable approaches are used to estimate complier average causal effects. We extend these approaches to cost-effectiveness analyses, where methods need to recognize the correlation between cost and health outcomes. We propose a Bayesian full likelihood approach, which jointly models the effects of random assignment on treatment received and the outcomes, and a three-stage least squares method, which acknowledges the correlation between the end points and the endogeneity of the treatment received. This investigation is motivated by the REFLUX study, which exemplifies the setting where compliance differs between the randomized controlled trial and routine practice. A simulation is used to compare the methods' performance. We find that failure to model the correlation between the outcomes and treatment received correctly can result in poor confidence interval coverage and biased estimates. By contrast, Bayesian full likelihood and three-stage least squares methods provide unbiased estimates with good coverage.

Sonographers' self-reported visualization of normal postmenopausal ovaries on transvaginal ultrasound is not reliable: results of expert review of archived images from UKCTOCS.

OBJECTIVE: In the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS), self-reported visualization rate (VR) of the ovaries by the sonographer on annual transvaginal sonographic (TVS) examinations was a key quality control (QC) metric. The objective of this study was to assess self-reported VR using expert review of a random sample of archived images of TVS examinations from UKCTOCS, and then to develop software for measuring VR automatically. METHODS: A single expert reviewed images archived from 1000 TVS examinations selected randomly from 68 931 TVS scans performed in UKCTOCS between 2008 and 2011 with ovaries reported as 'seen and normal'. Software was developed to identify the exact images used by the sonographer to measure the ovaries. This was achieved by measuring caliper dimensions in the image and matching them to those recorded by the sonographer. A logistic regression classifier to determine visualization was trained and validated using ovarian dimensions and visualization data reported by the expert. RESULTS: The expert reviewer confirmed visualization of both ovaries (VR-Both) in 50.2% (502/1000) of the examinations. The software identified the measurement image in 534 exams, which were split 2:1:1 providing training, validation and test data. Classifier mean accuracy on validation data was 70.9% (95% CI, 70.0-71.8%). Analysis of test data (133 exams) provided a sensitivity of 90.5% (95% CI, 80.9-95.8%) and specificity of 47.5% (95% CI, 34.5-60.8%) in detecting expert confirmed visualization of both ovaries. CONCLUSIONS: Our results suggest that, in a significant proportion of TVS annual screens, the sonographers may have mistaken other structures for normal ovaries. It is uncertain whether or not this affected the sensitivity and stage at detection of ovarian cancer in the ultrasound arm of UKCTOCS, but we conclude that QC metrics based on self-reported visualization of normal ovaries are unreliable. The classifier shows some potential for addressing this problem, though further research is needed. © 2017 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Systematic Review and Meta-Analysis of Utility of Graduated Compression Stockings in Prevention of Post-Thrombotic Syndrome.

BACKGROUND: Up to 50% of patients develop post-thrombotic syndrome (PTS) following their first proximal deep vein thrombosis (DVT). This meta-analysis aims to evaluate the effectiveness of graduated compression stockings (GCS) in preventing PTS. METHOD: Medline, Embase, Cochrane Database of Systematic Reviews, and ClinicalTrials.gov were electronically searched from inception to January 2015 for studies investigating the effect of GCS in preventing PTS. All randomised control trials were considered for inclusion if they compared the efficacy of GCS (30-40 mmHg at the ankle) with either placebo or no stockings in adults with new proximal lower limb DVT. Methodological assessment, using the Cochrane Risk of Bias Tool, and data extraction was performed by two independent reviewers. The effect of GCS was expressed as the risk difference (RD). RESULTS: A total of 686 articles were screened. Three randomised controlled trials inclusive of 1,177 patients were eligible for inclusion. PTS developed in 49-70% of control patients at 5 years. High statistical heterogeneity was observed between trials (all PTS: I(2) = 0.94; severe PTS: I(2) = 0.79). The risk difference in PTS incidence between control and GCS arms varied from 0% to 39% between trials. In trials with a higher baseline prevalence of PTS, a visual trend towards more benefit with GCS was noted. CONCLUSION: Uncertainty because of sampling variability and heterogeneity was too high to conclude in favour or against an effect of wearing compression stockings in preventing PTS. An effect may be present for higher values of baseline risk. Further evidence is needed. Article history.

A pragmatic randomised controlled trial of the effectiveness and cost-effectiveness of 'PhysioDirect' telephone assessment and advice services for physiotherapy.

BACKGROUND: As a result of long delays for physiotherapy for musculoskeletal problems, several areas in the UK have introduced PhysioDirect services in which patients telephone a physiotherapist for initial assessment and treatment advice. However, there is no robust evidence about the effectiveness, cost-effectiveness or acceptability to patients of PhysioDirect. OBJECTIVE: To investigate whether or not PhysioDirect is equally as clinically effective as and more cost-effective than usual care for patients with musculoskeletal (MSK) problems in primary care. DESIGN: Pragmatic randomised controlled trial to assess equivalence, incorporating economic evaluation and nested qualitative research. Patients were randomised in 2 : 1 ratio to PhysioDirect or usual care using a remote automated allocation system at the level of the individual, stratifying by physiotherapy site and minimising by sex, age group and site of MSK problem. For the economic analysis, cost consequences included NHS and patient costs, and the cost of lost production. Cost-effectiveness analysis was carried out from the perspective of the NHS. Interviews were conducted with patients, physiotherapists and their managers. SETTING: Four community physiotherapy services in England. PARTICIPANTS: Adults referred by general practitioners or self-referred for physiotherapy for a MSK problem. INTERVENTIONS: Patients allocated to PhysioDirect were invited to telephone a senior physiotherapist for initial assessment and advice using a computerised template, followed by face-to-face care when necessary. Patients allocated to usual care were put on to a waiting list for face-to-face care. MAIN OUTCOME MEASURES: Primary outcome was the Short Form questionnaire-36 items, version 2 (SF-36v2) Physical Component Score (PCS) at 6 months after randomisation. Secondary outcomes included other measures of health outcome [Measure Yourself Medical Outcomes Profile, European Quality of Life-5 Dimensions (EuroQol health utility measure, EQ-5D), global improvement, response to treatment], wait for treatment, time lost from work and usual activities, patient satisfaction. Data were collected by postal questionnaires at baseline, 6 weeks and 6 months, and from routine records by researchers blind to allocation. RESULTS: A total of 1506 patients were allocated to PhysioDirect and 743 to usual care. Patients allocated to PhysioDirect had a shorter wait for treatment than those allocated to usual care [median 7 days vs 34 days; arm-time ratio 0.32, 95% confidence interval (CI) 0.29 to 0.35] and had fewer non-attended face-to-face appointments [incidence rate ratio 0.55 (95% CI 0.41 to 0.73)]. The primary outcome at 6 months' follow-up was equivalent between PhysioDirect and usual care [mean PCS 43.50 vs 44.18, adjusted difference in means -0.01 (95% CI -0.80 to 0.79)]. The secondary measures of health outcome all demonstrated equivalence at 6 months, with slightly greater improvement in the PhysioDirect arm at 6 weeks' follow-up. Patients were equally satisfied with access to care but slightly less satisfied overall with PhysioDirect compared with usual care. NHS costs (physiotherapy plus other relevant NHS costs) per patient were similar in the two arms [PhysioDirect £ 198.98 vs usual care £ 179.68, difference in means £ 19.30 (95% CI -£ 37.60 to £ 76.19)], while QALYs gained were also similar [difference in means 0.007 (95% CI -0.003 to 0.016)]. Incremental cost per QALY gained was £ 2889. The probability that PhysioDirect was cost-effective at a £ 20,000 willingness-to-pay threshold was 88%. These conclusions about cost-effectiveness were robust to sensitivity analyses. There was no evidence of difference between trial arms in cost to patients or value of lost production. No adverse events were detected. CONCLUSIONS: Providing physiotherapy via PhysioDirect is equally clinically effective compared with usual waiting list-based care, provides faster access to treatment, appears to be safe, and is broadly acceptable to patients. PhysioDirect is probably cost-effective compared with usual care.

[Ergonomics, hygiene and rationality: the "electric house" of Monza (1930)]. / Ergonomia, igiene e razionalità: la "casa elettrica" di Monza (1930).

The "Electric House" of Monza is seen as one of the early example of rationalist architecture produced in Italy. Sponsored by the Italian Edison General Company for Electricity and produced by the Group 7, it was built for the "IV International Triennial Exhibition of Decorative and Modern Industry Arts", held in Monza in 1930. It was conceived as an environment in which the designers showed their interest towards new concepts of rationalist hygiene. Special care was taken to select the environments in relation to the surrounding nature and the needs of life of the house inhabitants: new materials more comfortable, hygienic and rational were inserted. In the kitchen, for example, the architect P. Bottoni, created a space in which the housewife's work was marked by lower energy expenditure, thanks to a careful study of the actions and movements according to the principles of taylorism, here applied to domestic work.

Accounting for correlation in network meta-analysis with multi-arm trials.

Multi-arm trials (trials with more than two arms) are particularly valuable forms of evidence for network meta-analysis (NMA). Trial results are available either as arm-level summaries, where effect measures are reported for each arm, or as contrast-level summaries, where the differences in effect between arms compare with the control arm chosen for the trial. We show that likelihood-based inference in both contrast-level and arm-level formats is identical if there are only two-arm trials, but that if there are multi-arm trials, results from the contrast-level format will be incorrect unless correlations are accounted for in the likelihood. We review Bayesian and frequentist software for NMA with multi-arm trials that can account for this correlation and give an illustrative example of the difference in estimates that can be introduced if the correlations are not incorporated. We discuss methods of imputing correlations when they cannot be derived from the reported results and urge trialists to report the standard error for the control arm even if only contrast-level summaries are reported. Copyright © 2012 John Wiley & Sons, Ltd.

Effects of the commensurability and disorder on friction for the system Xe/Cu.

We present molecular dynamics simulations of static friction for a monolayer of Xe deposited on a thick slab of Cu for two different geometries. The interaction potential between Xe and Cu has been derived from DFT calculations. The first geometry is the commensurate adsorption geometry (√3 × âˆš3 suggested by LEED, corresponding to a coverage 1/3, where all Xe atoms are on top positions. The second one corresponds to a coverage 0.36 and is characterized by a large surface unit cell, containing 9 Xe atoms in different disordered positions. This large unit cell mimics an incommensurate case. Our analysis points out the effect of the order/disorder in tribological properties of a realistic three-dimensional system.

Gut microbiota as a candidate for lifespan extension: an ecological/evolutionary perspective targeted on living organisms as metaorganisms.

An emerging central concept in evolutionary biology suggests that symbiosis is a universal characteristic of living organisms that can help in understanding complex traits and phenotypes. During evolution, an integrative circuitry fundamental for survival has been established between commensal gut microbiota and host. On the basis of recent knowledge in worms, flies, and humans, an important role of the gut microbiota in aging and longevity is emerging. The complex bacterial community that populates the gut and that represents an evolutionary adapted ecosystem correlated with nutrition appears to limit the accumulation of pathobionts and infections in all taxa, being able of affecting the efficiency of the host immune system and exerting systemic metabolic effects. There is an urgent need to disentangle the underpinning molecular mechanisms, which could shed light on the basic mechanisms of aging in an ecological perspective. Thus, it appears possible to extend healthy aging and lifespan by targeting the host as a metaorganism by manipulating the complex symbiotic ecosystem of gut microbiota, as well as other possible ecosystems of the body.

Effect of fast-, medium- and slow-growing strains on meat quality of chickens reared under the organic farming method.

The characteristics of meat quality, chemical and fatty acid composition, from fast-growing (FG) and medium-growing (MG) meat-type and slow-growing (SG) egg-type chickens reared under organic conditions were compared. Three-hundred and sixty 1-day-old male chicks, equally divided into three experimental groups represented by strains (FG: Cobb 700, MG: Naked neck Kabir and SG: Brown Classic Lohman) were housed into three poultry houses with outdoor pasture availability of 10 m(2)/bird located in the same Research Centre of the University of Perugia. All the birds were fed ad libitum the same diets formulated according to the European Union (EU) Regulations by using organic raw materials. Birds from the FG and MG groups were raised until 81 days, whereas birds from the SG group were raised until 96 days in order to achieve an acceptable market live weight. SG birds showed significantly (P < 0.01) higher breast meat drip and cook losses, Allo-Kramer shear values and collagen content. In comparison with FG and SG, MG exhibited a higher breast meat pH (5.86% v. 5.79% and 5.78%, respectively; P < 0.01) and a lower lightness (54.88% v. 57.81% and 56.98%, respectively; P < 0.05). Genotype dramatically affected the lipid content as well as the fatty acid composition of both breast and thigh meat. SG exhibited the lowest content of lipid, both in breast and in thigh meat, the lowest proportions of monounsaturated fatty acids (MUFA) and the highest proportions of polyunsaturated fatty acids (PUFA). The total n-3 PUFA of SG breast meat was double that of FG meat and intermediate with respect to MG birds (8.07% v. 4.07% v. 5.14% total fatty acids; P < 0.01). The fatty acid composition of thigh meat is similar to that of breast meat, but the differences among genotypes are less pronounced. Total saturated fatty acids were not affected by the genotype. In conclusion, meat functional properties of FG and MG strains appeared much more attractive both for industry and consumer (lower drip and cook losses and higher tenderness), whereas from a nutritional point of view, meat from SG appeared healthier (less fat and higher content of n-3 PUFA) and thus might better fit with the consumer's expectations of organic products.

[Work and medicine in Manuali Hoepli series]. / Il lavoro e la medicina nei Manuali Hoepli.

The Authors analyse the Italian, technical series called Manuali Hoepli, devoted to promote technical knowledge in the second half of XIXth century. Johann Ulrich (Ulrico) Hoepli (1847-1935) came from Switzerland to Milan in 1870, and translated into Italian some volumes edited by Macmillan in London (from Science Primers series). During his life, he printed 2000 Manuali Hoepli. Some of them were devoted to Occupational Medicine. Five volumes are presented: Magrini's one was devoted to technical devices to prevent industrial accidents; Allevi's Manual was printed when Milan Clinica del Lavoro was preparing; Altarelli and Bortolotto's manuals show us the fascist way of social medicine.

Inflammatory response in molluscs: cross-taxa and evolutionary considerations.

Inflammation represents the rapid and efficient elimination of damaged tissue and microbes and eventually the restoration of tissue functionality. Inflammatory response is one of the vital reactions to body injury, acting alongside the restoration of homeostasis, wound repair and immune response. In mammals, wound healing is a process that seeks to restore tissue integrity and function, and is characterized by a series of biological processes including inflammatory response. Here, we review pioneering experiments and recent observations in invertebrate models suggesting that in highly divergent and evolutionary distant taxa, such as molluscs, insects and vertebrates, the inflammatory response could be driven by a pool of molecules sharing common evolutionary origin.

Hot air treatment for surface decontamination of table eggs experimentally infected with Salmonella, Listeria, and Escherichia coli.

Hot-air pasteurization was investigated in the EU-funded project "Reducing Egg Susceptibility to Contaminations in Avian Production in Europe (RESCAPE)" as an innovative treatment for surface bacterial decontamination of table eggs. Possible side effects of the treatment on egg quality traits were also studied. The decontamination power of hot air was evaluated over 1 month on shell eggs that were experimentally inoculated with Salmonella enteritidis, Escherichia coli, or Listeria monocytogenes. The S. Enteritidis and L. monocytogenes populations on the surfaces of treated eggs showed a significant reduction compared with untreated eggs. No statistically significant results were obtained comparing E. coli loads on treated and untreated eggs. No detrimental effects on quality traits either immediately after treatment or after 28 days of storage at 20 degrees C were recorded.

Sliding friction of N2 on Pb(111).

Molecular dynamics simulations of the sliding friction between two thick solid slabs are performed. The upper body is formed of light N(2) particles and the substrate of heavy Pb atoms. Among the various mechanisms that are responsible for the friction, we consider the phonon-phonon interaction between the two blocks. To provide evidence of the phonon interaction, we compare two different systems. For the first we consider the substrate as formed of atoms fixed in the equilibrium (111) positions. In the second system the Pb atoms can be displaced from the ideal positions, under their mutual interactions. A comparison with recently obtained experimental data will be discussed.