Exponential separations using guarded extension variables

We study the complexity of proof systems augmenting resolution with inference rules that allow, given a formula $\Gamma$ in conjunctive normal form, deriving clauses that are not necessarily logically implied by $\Gamma$ but whose addition to $\Gamma$ preserves satisfiability. When the derived clauses are allowed to introduce variables not occurring in $\Gamma$, the systems we consider become equivalent to extended resolution. We are concerned with the versions of these systems without new variables. They are called BC${}^-$, RAT${}^-$, SBC${}^-$, and GER${}^-$, denoting respectively blocked clauses, resolution asymmetric tautologies, set-blocked clauses, and generalized extended resolution. Each of these systems formalizes some restricted version of the ability to make assumptions that hold "without loss of generality," which is commonly used informally to simplify or shorten proofs. Except for SBC${}^-$, these systems are known to be exponentially weaker than extended resolution. They are, however, all equivalent to it under a relaxed notion of simulation that allows the translation of the formula along with the proof when moving between proof systems. By taking advantage of this fact, we construct formulas that separate RAT${}^-$ from GER${}^-$ and vice versa. With the same strategy, we also separate SBC${}^-$ from RAT${}^-$. Additionally, we give polynomial-size SBC${}^-$ proofs of the pigeonhole principle, which separates SBC${}^-$ from GER${}^-$ by a previously known lower bound. These results also separate the three systems from BC${}^-$ since they all simulate it. We thus give an almost complete picture of their relative strengths

Exponential Separations Using Guarded Extension Variables

We study the complexity of proof systems augmenting resolution with inference rules that allow, given a formula ? in conjunctive normal form, deriving clauses that are not necessarily logically implied by ? but whose addition to ? preserves satisfiability. When the derived clauses are allowed to introduce variables not occurring in ?, the systems we consider become equivalent to extended resolution. We are concerned with the versions of these systems without new variables. They are called BC?, RAT?, SBC?, and GER?, denoting respectively blocked clauses, resolution asymmetric tautologies, set-blocked clauses, and generalized extended resolution. Each of these systems formalizes some restricted version of the ability to make assumptions that hold "without loss of generality," which is commonly used informally to simplify or shorten proofs. Except for SBC?, these systems are known to be exponentially weaker than extended resolution. They are, however, all equivalent to it under a relaxed notion of simulation that allows the translation of the formula along with the proof when moving between proof systems. By taking advantage of this fact, we construct formulas that separate RAT? from GER? and vice versa. With the same strategy, we also separate SBC? from RAT?. Additionally, we give polynomial-size SBC? proofs of the pigeonhole principle, which separates SBC? from GER? by a previously known lower bound. These results also separate the three systems from BC? since they all simulate it. We thus give an almost complete picture of their relative strengths

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

The liability of the carrier i·n the contract of i·nternational air transport of passengers and cargo

YÖK Tez ID: 411812Havayoluyla Yapılan Uluslararası yük ve yolcu taşıma sözleşmelerini düzenleyen uluslararası konvansiyonların getirdiği hükümlerin büyük çoğunluğu taşıyıcının sorumluluğuna ilişkindir. Çalışmamızın amacı yakın bir tarihte ülkemiz açısından yürürlüğe giren 1999 Montreal Konvansiyonu'nun ve halen uygulama alanı bulan Varşova/Lahey sisteminin taşıyıcının sorumluluğuna ilişkin hükümlerini, 1929 Varşova Konvansiyonu, 1955 Lahey Protokolü, 1961 Guadalajara Ek Konvansiyonu, 1966 Montreal Geçici Anlaşması, 1973 Guatemala City Protokolleri, 1975 Montreal Protokolleri'nin getirdiği prensipler ve bu düzenlemelere hâkim olan hukuki gerçeklikler ve gerekçeler doğrultusunda incelemektir. Uluslararası hava taşımalarına uygulanacak olan hukuk kuralları bakımından ülkeler arasında farklı düzenlemelerin olması, yaşanan benzer ihtilaflarda farklı sonuçların ortaya çıkmasına neden olacaktır. Yukarıda belirtilen uluslararası düzenlemeler de bu sakıncayı gidermek amacıyla başlatılan yeknesaklaştırma çabalarının bir ürünüdür. 1929 Varşova Konvansiyonu ile başlayıp 1999 Montreal Konvansiyonu'na kadar devam eden süreçte gelişen ve değişen sivil hava taşımacılığı sektörünün ihtiyaçları, bu süreç içerisinde yukarıda kronolojik olarak sıralaması verilen uluslararası düzenlemelerle giderilmeye ve güncellenmeye çalışılmıştır. Uluslararası yük ve yolcu taşıma sözleşmelerinde, meydana gelen zararlardan konvansiyon hükümleri neticesinde sorumlu tutulabilecek olan taşıyıcı sıfatına, kimlerin sahip olduğunun yine konvansiyon hükümleri uyarınca tespit edilmesi gerekmektedir. Bu nedenle çalışmamızda akdi taşıyıcı, fiili taşıyıcı, mütevali taşıyıcı gibi kavramlar üzerinde durulmuştur. Uluslararası konvansiyonlarda, konvansiyon hükümlerinin uygulanma şartları, taşıyıcının sorumluluğuna ilişkin olarak konvansiyon hükümlerinde öngörülen sorumluluk rejimlerinin hukuki niteliği, taşıyıcının uluslararası konvansiyon hükümleri çerçevesinde hangi hallerde sorumlu tutulacağı ve taşıyıcının sorumluluğunun kapsam ve sınırları konularına da yer verilmiştir. Yine uluslararası düzenlemeler neticesinde taşıyıcının sorumluluğunun söz konusu olabileceği; yolcunun ölümü, yaralanması, bagaj veya yükün ziyaı veya hasara uğraması, yolcu bagaj ve yük taşımalarındaki gecikme hallerinde taşıyıcının sorumluluğuna gidilebilmesi için aranan şartlar da bu düzenlemelerde yer bulmuştur. Ayrıca taşıyıcıya bağımlı veya bağımsız olarak çalışan taşıyıcının adamlarının fillerinden de taşıyıcının hangi şartlar altında sorumlu tutulacağı tespit edilmiştir. Son olarak uluslararası düzenlemelerde yolcu ve yük taşımaları bakımından taşıyıcının sorumlu olduğu durumlarda açılabilecek tazminat davası, tazminat miktarı ve hesaplanması, dava sebebi ve davanın tarafları konularına da değinilmiştir.Vast majority of provisions the international conventions which regulates the International Air Transport of passengers and baggage have brought about are concerned with the responsibility of the carrier. The purpose of this study is to investigate the provisions concerning the responsibility of the carrier in The Montreal Convention (1999) which has been come into force recently in our country and in the Warsaw/Lahey system which is still in operation in line with the judicial reality and justifications as well as the principles brought about by 1929 Warsaw Convention, 1955 Lahey Protocol, 1961 Guadalajara Convention, 1966 Montreal Temporary Convention, 1973 Guatemala City Protocols, 1975 Montreal Protocols. That there are different regulations among countries in terms of legal rules that will be administered to international air transport leads to the occurrence of different results in similar controversies. The international regulations stated above are the outcomes of an attempt started to bring uniformity so as to remove this inconvenience. Within the period starting with the 1929 Warsaw Convention and continuing up until the 1999 Montreal Convention, the needs of developing and changing civil air transportation have been tried to be met and updated with the international regulations, the chronological order of which is provided above. It's important to determine the carrier who is responsible for the occurring damage and it must be determine in accordance with the articles of convention on International Air Transport of passengers and baggage contracts. That's the reason we mention the concepts like conventional carrier, actual carrier and successive carrier. And this work also includes; implementation fundamentals of international convention rules, legal nature of responsibility regimes which foreseen in convention rules concerning the responsibility of the carrier, in which situations the carrier will be responsible within the frame of international convention rules and extant and limits of the responsibility of the carrier. Also; the situations which carrier can be responsible as a result of international regulations, the death or injury of the passenger, the damage or loss of the passage or load, conditions of the carriers responsibility in case of delay of the passenger, baggage or load have been investigated. Besides; under which circumstances carrier can be responsible for his dependent or independent workers' actions determined in this work. Finally, in international regulations, when the carrier is responsible concerning the carriage of passengers and baggage, the issues about suing for damage, calculation and sum of compensation, ground of action and the parties of action have been investigated

Use of three dimensional printed models in the training of medical students in pediatric surgery: First impressions Çocuk cerrahisi öǧrenci eǧitiminde üç boyutlu modellerin kullanilmasi: Süreç ve ilk izlenimler

2017 © Logos Medical Publishing. All Rights Reserved.Aim: The aim of this study is to present the process of the manufacturing three-dimensional (3d) printed educational models and our experiences related to using these models in the training of pediatric surgery students. Material and Methods: Models of five main congenital disease groups related to pediatric surgery (esophageal atresia, anorectal malformations, vesicoureteral reflux, choledochal cysts, jejunoileal atresias) were designed using a 3-dimensional computerized program. The models printed using 3D printers were passed through post-production processes. These models were used for training purposes in students' theoretical and practical curriculum during internship of the fifth grade medical students' in 3 groups in 2018. Feedbacks were obtained with the post-internship surveys throughout one semester. Results: Design and printing processes of all planned models were achieved. The survey feedbacks showed that the students who were in the groups which these models were used in theoretical and practical lessons reported their satisfaction with these models. There was no negative feedback. Conclusion: Within the frame of this study models of the diseases specific to pediatric surgery were produced using 3D printers. With use of 3D not only printed materials but also augmented reality and enriched education are becoming possible options. The survey results indicated that these models have positive effects on the "students' education" in pediatric surgery

Three dimensional printers and pediatric surgery Üç boyutlu yazıcılar ve çocuk cerrahisi

© Cocuk Cerrahisi Dergisi. All rights reserved.The use and coverage of 3d printers increased progressively as a result of developments in printing technology and soft-wares. A novel productive method other than conventional industrial design and production perception, low-cost and personalised production potential resulted with the help of rapid prototyping in an increase of personal creativity and novel ideas. As well as in a wide selection of fields of use, progress in health practice also arised rapidly. Recent areas of 3d printers increase daily in a wide selection of disciplines such as pharmacy, surgery, medical instrumentation, orthesis/prothesis production, organ and tissue production and medical education. In this current review utilization of 3d printers in medicine, and current data regarding their use in surgery and especially in pediatric surgery were evaluated and opinions regarding prospective areas of use are presented

Artirilmiş gerçekliǧin tipta ve çocuk cerrahisinde kullanimi

© 2018 Logos Medical Publishing. All Rights Reserved.Virtual technologies (virtual reality, augmented reality and hologram) were started to be used in many areas of life, along with the widespread use of mobile tools. The use of augmented reality in medicine, which is a method based on the perception of digital visual content as in real life, is also increasing. In this article, current and possible applications of augmented reality technology in academic life, medicine and pediatric surgery were evaluated and examples for practical applications were given

Constructing low-cost simulation models in pediatric surgery and pediatric urology using 3D printing and hydrogel: Preliminary study Üç boyutlu yazici ve hidrojel kullanarak düşük maliyetli çocuk cerrahisi ve çocuk ürolojisi simülasyon modelleri üretimi: Ön çalişma

© 2019 Logos Medical Publishing. All Rights Reserved.Objective: Using surgical education simulations to develop and maintain fine motor skills becomes gradually more important and prevalent in hands-on-training of both students and surgery/urology residents. However, these simulation-training models should overcome problems of individualized design, high cost, and inability to reflect accurate anatomy and tissue characteristics, by means of new research studies. In this study, we aimed to construct affordable training-simulation models for student-resident training in pediatric surgery and urology using a 3D printer and polyvinyl alcohol (PVA). Material and Methods: In this study virtual models of the renal mass lesions and urinary system stone disease that are frequently encountered problems in pediatric surgery and urology using 3Ds MAX software (Autodesk, San Rafael, CA). Virtual models were used as reference geometry to design molds in Fusion 360 software (Autodesk, San Rafael, CA). After inverse geometries of the virtual models were constructed, supportive l features such as inlet and outlet pipes were added to the mold using Boolean operations. Generated molds were printed using Ultimaker 2+ 3D printer (Ultimaker B.V, Geldermalsen, The Netherlands). The %20 w/v solution of the PVA was prepared and injected between the 3D-printed molds. Five freeze-thaw cycles were subsequently administered to the entire molds to allow the PVA molecules to create hydrogen bonds that lead to forming the tissue-mimicking gel. The training-simulation models were removed from the molds. Results: In this study, the kidney and urinary bladder models were produced. Conclusions: In this preliminary study, we demonstrated how to construct anatomically correct, low-cost, procedure-specific models that mimic the original properties of living tissues. The utility of the models in student and resident education will be evaluated in future studies