On the Approximability of Multistage Min-Sum Set Cover

We investigate the polynomial-time approximability of the multistage version of Min-Sum Set Cover ($\mathrm{DSSC}$), a natural and intriguing generalization of the classical List Update problem. In $\mathrm{DSSC}$, we maintain a sequence of permutations $(\pi^0, \pi^1, \ldots, \pi^T)$ on $n$ elements, based on a sequence of requests $(R^1, \ldots, R^T)$. We aim to minimize the total cost of updating $\pi^{t-1}$ to $\pi^{t}$, quantified by the Kendall tau distance $\mathrm{D}_{\mathrm{KT}}(\pi^{t-1}, \pi^t)$, plus the total cost of covering each request $R^t$ with the current permutation $\pi^t$, quantified by the position of the first element of $R^t$ in $\pi^t$. Using a reduction from Set Cover, we show that $\mathrm{DSSC}$ does not admit an $O(1)$-approximation, unless $\mathrm{P} = \mathrm{NP}$, and that any $o(\log n)$ (resp. $o(r)$) approximation to $\mathrm{DSSC}$ implies a sublogarithmic (resp. $o(r)$) approximation to Set Cover (resp. where each element appears at most $r$ times). Our main technical contribution is to show that $\mathrm{DSSC}$ can be approximated in polynomial-time within a factor of $O(\log^2 n)$ in general instances, by randomized rounding, and within a factor of $O(r^2)$, if all requests have cardinality at most $r$, by deterministic rounding

The Histological and Immunohistochemical Aspects of Bile Reflux in Patients with Gastroesophageal Reflux Disease

Introduction. The pathogenesis of GERD is strongly related with mixed acid and bile reflux. Benign and malignant esophageal and gastric lesions have been associated with synergetic activity between those parameters. Bile reflux causes reactive gastropathy evaluated with Bile Reflux Index (BRI). The aim was to investigate if the sequence: bile reflux-intestinal metaplasia-GERD-esophagitis, is associated with apoptotic/oncogenetic disturbances. Materials/Methods. Fifteen asymptomatic subjects and 53 GERD patients underwent gastroscopy with biopsies. The specimens examined histologically and immunohistochemically for p53, Ki-67, Bax, and Bcl-2. Results. Elevated BRI score detected in 47% (25/53) of patients with GERD and in 13% (2/15) of controls (P = 0.02). Severe esophageal lesions were significantly more common in BRI (+) patients (14/25) compared to BRI (−) ones (P = 0.0049). Immunohistochemical analysis did not show associations between BRI score and biomarker expression. Conclusions. Bile reflux gastropathy is associated with GERD severity, but not with oncogene expression or apoptotic discrepancies of the upper GI mucosa

Effekten av två olika kompressionslindor vid läkning av venösa bensår

SAMMANFATTNING    Bakgrund: Venösa bensår är ett globalt vanligt förekommande fenomen, 1–2 % av jordens befolkning anses vara drabbade. Bensår skapar stort lidande för patientens fysiska och psykiska hälsa. Två vanliga förekommande problem är smärta och isolering. Det finns flera metoder för att läka venösa bensår där flerlagers-kompressionslinda anses vara en av det bästa metoderna. Att läka bensår skulle kunna minska patientlidandet.    Syfte: Att sammanställa och jämföra läkningseffekten av två- och fyra-lagerskompressionslindning hos patienter med venösa bensår.   Metod: En deskriptiv design med litteraturöversikt användes som metod där tio vetenskapliga kvantitativa originalartiklar inkluderades. Artikelsökning gjordes i databaserna PubMed och CINAHL.   Resultat: Litteraturöversikten kunde inte påvisa en skillnad mellan 2LB- och 4LB-kompressiongrupperna för förbättrad och fullständig läkningsförmåga. Båda lindorna bekräftades ha en sårläkande effekt. Effekten av kompressionslindorna gav en mer påskyndad sårläkning, än hos patienter utan kompressionsbehandling. Majoriteten av de inkluderade studierna visade på ett liknande resultat i fullständig procentuell läkning mellan två-lagerkompressionslindning (2LB) och fyra-lagerkompressionslindning (4LB).   Slutsats: Litteraturöversikten visar att kompressionsbehandling med 2LB och 4LB har en likvärdig och god sårläkande effekt för patienter. Både 2LB och 4LB är mer gynnsam för sårläkning och välmående än utan kompressionsbehandling för patienter som lever med venösa bensår.ABSTRACT Background: Venous leg ulcers is a globally common phenomenon, 1-2 % of the world’s population is believed to be affected. Leg ulcers causes great suffering for the patient's physical and mental health. Two common complications are pain and isolation. There are several methods to heal venous leg ulcers, multilayer-compression-therapy is considered one of the best methods. Healing leg ulcers could reduce patient suffering. Purpose: To compile and compare the healing effects of two- and four-layer compression therapy in patients with venous leg ulcers.   Method: A descriptive design with a literature review as method, with ten scientific quantitative original articles were included. Article searches was done in databases PubMed and CINAHL.   Results: The results did not show a difference between the 2LB and 4LB-groups regarding complete and improved healing. However, both methods had a healing effect. The bandages were more effective in accelerating healing in patients, than in patients without compression therapy. Most of the included studies showed a similar result in the percentage of complete healing effect between the two-layer compression therapy (2LB) and four-layer compression therapy (4LB).   Conclusion: This literature review demonstrated that compression therapy with 2LB and 4LB has an equally as well as good healing effect for patients. Both 2LB and 4LB are significantly more beneficial for wound healing and well-being than without compression therapy for patients living with venous leg ulcers

Effekten av två olika kompressionslindor vid läkning av venösa bensår

SAMMANFATTNING    Bakgrund: Venösa bensår är ett globalt vanligt förekommande fenomen, 1–2 % av jordens befolkning anses vara drabbade. Bensår skapar stort lidande för patientens fysiska och psykiska hälsa. Två vanliga förekommande problem är smärta och isolering. Det finns flera metoder för att läka venösa bensår där flerlagers-kompressionslinda anses vara en av det bästa metoderna. Att läka bensår skulle kunna minska patientlidandet.    Syfte: Att sammanställa och jämföra läkningseffekten av två- och fyra-lagerskompressionslindning hos patienter med venösa bensår.   Metod: En deskriptiv design med litteraturöversikt användes som metod där tio vetenskapliga kvantitativa originalartiklar inkluderades. Artikelsökning gjordes i databaserna PubMed och CINAHL.   Resultat: Litteraturöversikten kunde inte påvisa en skillnad mellan 2LB- och 4LB-kompressiongrupperna för förbättrad och fullständig läkningsförmåga. Båda lindorna bekräftades ha en sårläkande effekt. Effekten av kompressionslindorna gav en mer påskyndad sårläkning, än hos patienter utan kompressionsbehandling. Majoriteten av de inkluderade studierna visade på ett liknande resultat i fullständig procentuell läkning mellan två-lagerkompressionslindning (2LB) och fyra-lagerkompressionslindning (4LB).   Slutsats: Litteraturöversikten visar att kompressionsbehandling med 2LB och 4LB har en likvärdig och god sårläkande effekt för patienter. Både 2LB och 4LB är mer gynnsam för sårläkning och välmående än utan kompressionsbehandling för patienter som lever med venösa bensår.ABSTRACT Background: Venous leg ulcers is a globally common phenomenon, 1-2 % of the world’s population is believed to be affected. Leg ulcers causes great suffering for the patient's physical and mental health. Two common complications are pain and isolation. There are several methods to heal venous leg ulcers, multilayer-compression-therapy is considered one of the best methods. Healing leg ulcers could reduce patient suffering. Purpose: To compile and compare the healing effects of two- and four-layer compression therapy in patients with venous leg ulcers.   Method: A descriptive design with a literature review as method, with ten scientific quantitative original articles were included. Article searches was done in databases PubMed and CINAHL.   Results: The results did not show a difference between the 2LB and 4LB-groups regarding complete and improved healing. However, both methods had a healing effect. The bandages were more effective in accelerating healing in patients, than in patients without compression therapy. Most of the included studies showed a similar result in the percentage of complete healing effect between the two-layer compression therapy (2LB) and four-layer compression therapy (4LB).   Conclusion: This literature review demonstrated that compression therapy with 2LB and 4LB has an equally as well as good healing effect for patients. Both 2LB and 4LB are significantly more beneficial for wound healing and well-being than without compression therapy for patients living with venous leg ulcers

A comparative study of tolerability amongst three different techniques for esophageal endoscopy: sedated conventional, unsedated peroral ultra thin, and esophageal capsule

INTRODUCTION. Three methods of esophagoscopy are available until now: sedated conventional endoscopy, unsedated ultrathin endoscopy, and esophageal capsule endoscopy. The three methods carry comparable diagnostic accuracy and different complication rates. Although all of them have been found well accepted from patients, no comparative study comprising the three techniques has been published. ΑΙΜ: The aim of this study was to compare the three methods of esophagoscopy regarding tolerability, satisfaction, and acceptance towards patients suffering from gastrointestinal disorders. PATIENTS-METHODS: Twenty patients with large esophageal varices and 10 with gastroesophageal reflux disease were prospectively included. All patients underwent consecutively sedated conventional endoscopy, unsedated ultrathin endoscopy, and esophageal capsule endoscopy. After each procedure, patients completed a 39-item and a 7-item questionnaires. RESULTS: The total positive attitude of patients toward all methods was high. However, statistical analysis revealed the following differences in favor of esophageal capsule endoscopy: (i) total positive attitude has been found higher (P < 0.001), (ii) similar findings have been found for tolerance, satisfaction and acceptance separately (iii) less patients felt pain (P = 0.03) and discomfort (P=0.01), (iv) less patients experienced difficulty (P = 0.01), and (v) more patients were willing to undergo esophageal capsule endoscopy in the future (P = 0.002). CONCLUSION: Esophageal capsule endoscopy was characterized by a more positive general attitude and caused less pain and discomfort. Sedated conventional endoscopy has been found more difficult. More patients would repeat esophageal capsule endoscopy in the future. Patients’ total position for all three available techniques for esophageal endoscopy was excellent and renders the observed advantage of esophageal capsule endoscopy over both sedated conventional and unsedated ultrathin endoscopy a statistical finding without a vital clinical benefit.Εισαγωγή: Τρεις μέθοδοι οισοφαγοσκόπησης (συμβατική υπό καταστολή, με ενδοσκόπιο μικρής διαμέτρου και οισοφαγική κάψουλα) είναι σήμερα διαθέσιμες. Οι τρεις μέθοδοι έχουν συγκρίσιμη διαγνωστική ακρίβεια, διαφέρουν στο ποσοστό των επιπλοκών και παρότι καθεμιά έχει ικανοποιητικά ποσοστά αποδοχής από τους ασθενείς, δεν έχουν συγκριθεί μεταξύ τους από την άποψη αυτή. Σκοπός: Η σύγκριση των τριών μεθόδων ως προς την ανοχή, την ικανοποίηση και την αποδοχή εκ μέρους των ασθενών Υλικό -Μέθοδοι: Είκοσι ασθενείς με μεγάλους οισοφαγικούς κιρσούς και 10 με γαστροοισοφαγική παλινδρομική νόσο αξιολογήθηκαν προοπτικά την τελευταία τριετία και υποβλήθηκαν διαδοχικά και στις τρεις μεθόδους. Μετά το πέρας των ενδοσκοπήσεων, οι ασθενείς συμπλήρωσαν δύο ειδικά ερωτηματολόγια, με 39 και 7 ερωτήσεις. Αποτελέσματα: Η συνολική θετική στάση των ασθενών ήταν ιδιαίτερη υψηλή προς όλες τις μεθόδους, σύμφωνα και με τα δύο ερωτηματολόγια. Ωστόσο, η οισοφαγική κάψουλα υπερείχε σημαντικά όσον αφορά τη γενική θετική στάση (p<0,001 και στα δύο ερωτηματολόγια) έναντι των άλλων δύο που βρέθηκαν ισοδύναμες. Παρόμοιες σχέσεις βρέθηκαν για την ανοχή, την ικανοποίηση και την αποδοχή ξεχωριστά. Λιγότεροι ασθενείς ένιωσαν πόνο (p=0,003), δυσανεξία (p<0,001) και δυσκολία (p=0,01) με τη κάψουλα. Περισσότεροι ήταν διατεθειμένοι να επαναλάβουν την κάψουλα στο μέλλον (p=0,002 ). Η συμβατική ενδοσκόπηση ήταν δυσκολότερη για τους ασθενείς Συμπεράσματα: Οι ασθενείς αντιμετώπισαν θετικά και τις τρεις μεθόδους. Η οισοφαγική κάψουλα υπερείχε των υπολοίπων στη συνολική θετική στάση και ξεχωριστά στην ανοχή, ικανοποίηση και αποδοχή. Η κάψουλα προκάλεσε λιγότερο συχνά πόνο και δυσφορία. Η συμβατική ενδοσκόπηση δυσκόλεψε περισσότερους ασθενείς. Περισσότεροι ασθενείς θα επαναλάμβαναν τη κάψουλα στο μέλλον. Τα υψηλά ποσοστά γενικής στάσης των ασθενών έναντι των τριών μεθόδων οισοφαγοσκόπησης καθιστούν την παρατηρηθείσα υπεροχή της κάψουλας ένα στατιστικό εύρημα χωρίς ιδιαίτερη κλινική σημασία

Η ποιότητα ως στοιχείο ανταγωνιστικότηταςα στους λιμένες σκαφών αναψυχής: η περίπτωση της Μαρίνας Αλίμου

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Επιστήμη και Τεχνολογία Υδατικών Πόρων

Complete Surgical Enucleation of a Giant Chylous Mesenteric Cyst

Mesenteric cysts are rare benign abdominal tumors, and they can appear anywhere in the mesentery of the gastrointestinal tract, from the duodenum to the rectum. They are generally asymptomatic and may present as an incidental finding. The diagnosis is confirmed by the laparotomy findings and the results of the histopathological examination. Complete surgical (open or laparoscopic) enucleation of the cyst is the treatment of choice. We present a case of a female patient who presented with abdominal pain and a giant palpable abdominal mass. The patient underwent a surgical exploration which showed a giant mesenteric cyst. A complete surgical enucleation of the cyst was successfully performed without the need of bowel resection. The histopathological examination of the cyst was compatible with the diagnosis of chylous mesenteric cyst