Distributed k-Means with Outliers in General Metrics

Center-based clustering is a pivotal primitive for unsupervised learning and data analysis. A popular variant is the k-means problem, which, given a set P of points from a metric space and a parameter k < |P|, requires finding a subset S ⊂ P of k points, dubbed centers, which minimizes the sum of all squared distances of points in P from their closest center. A more general formulation, introduced to deal with noisy datasets, features a further parameter z and allows up to z points of P (outliers) to be disregarded when computing the aforementioned sum. We present a distributed coreset-based 3-round approximation algorithm for k-means with z outliers for general metric spaces, using MapReduce as a computational model. Our distributed algorithm requires sublinear local memory per reducer, and yields a solution whose approximation ratio is an additive term O(γ) away from the one achievable by the best known polynomial-time sequential (possibly bicriteria) approximation algorithm, where γ can be made arbitrarily small. An important feature of our algorithm is that it obliviously adapts to the intrinsic complexity of the dataset, captured by its doubling dimension D. To the best of our knowledge, no previous distributed approaches were able to attain similar quality-performance tradeoffs for general metrics

Coreset-Based Algorithms for k-Means with Outliers

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Presentazione della TPM Total Productive Maintenance e analisi di casi industriali

TPM e analisi di casi studio dell'applicazione della TP

La tiroidectomia totale: esperienza iniziale di un centro di riferimento territoriale

Gli Autori riportano la loro iniziale esperienza nel trattamento chirurgico delle tireopatie in una provincia a relativa alta incidenza di tumori della tiroide. Di 428 pazienti visitati dall’inizio del 2006, sulla base della clinica, degli esami ematochimici e degli esami strumentali, tra cui anche l’agoaspirato ecoguidato, ne sono stati selezionati 134 per l’intervento chirurgico. Analizzati i dati dei primi 93 casi, operati sino al novembre 2006, vengono sottolineate le indicazioni terapeutiche, la tecnica chirurgica e soprattutto l’alta percentuale di reperti neoplastici

L’ematoma retroperitoneale post-traumatico

La gestione degli ematomi retroperitoneali post-traumatici risulta ancora molto controversa. Nonostante l’utilizzo della TC multiscan con mezzo di contrasto abbia di molto facilitato la fase diagnostica, le difficoltà di approccio e di decisioni terapeutiche derivano dalla molteplicità dei quadri clinici dovuti alla estrema varietà delle lesioni riscontrabili, sia semplici che, più frequentemente, associate. La casistica presentata riguarda 1086 casi trattati, che rappresentano il 29,5% dei 3682 politraumatizzati addominali ad impronta critica osservati nell’arco di 35 anni. La mortalità è stata del 12,9% con un ISS (Injury Severity Score) medio di 23.4. Prevalente il trauma chiuso: 71,4% vs 28,6%. Le lesioni singole più frequenti sono state quelle del bacino (43%) seguite da quelle renali (39%), mentretra le lesioni associate spiccano i traumi del torace causa di aumento sia del punteggio ISS che della mortalità rispettivamente fino a 26.2 e 14,6%. Interessante l’associazione con traumi maxillo-facciali (11%), dovuti soprattutto agli incidenti di moto che hanno subìto negli anni un incremento significativo passando dal 2,4% degli anni Settanta al 32% attuale. Il nostro atteggiamento verso questi traumatizzati è stato fondamentalmente conservativo. Sulla base delle indicazioni della TC con mezzo di contrasto, abbiamo fatto frequente ricorso all’angiografia interventistica, in particolare per lesioni renali ed ematomi pelvici, previa stabilizzazione del bacino. La decisione di procedere ad una soluzione chirurgica è stata presa in rapporto al tipo di trauma, se aperto o chiuso, alla localizzazione dell’ematoma e soprattutto all’evoluzione della situazione emodinamica

Twenty years exeperiences in treatment of pilonidal sinus with primary Closure.

Pilonidal sinus is a common disease among young adults after the puberty while it is quite rare in subjects older than 40 years. The incidence in the third and fourth decade and the prevalence of the disease in males, with a rate of 3:1 are probably related to androgen secretion. In case of abscess most of the authors suggest a conservative approach with incision and drainage under local anesthesia, delaying the definitive treatment by complete excision of the sinus. Nevertheless, surgical treatment of the sinus has an high recurrence rate and as shown by the several techniques proposed, choice primarily depends on the experience of the surgeon and on the consensus of the patient. Methods: From 1985 to 2004, 229 patients (171 M, 58 F) aged between 16 and 35 years, affected by pilonidal sinus were treated by complete excision of the sinus and primary closure. Results: Primary healing was achieved in 208 patients (91%) in an average time of 11.9 days. Secondary healing was achieved in 21 patients (9%) in 16–19 days. Mean postoperative hospital-stay was 1.9 days and average time off work was 16 days. Recurrent pilonidal sinus was observed in 10 patients with a mean follow-up of 30 months (range 12–60). Discussion: On the basis of their experience, the authors conclude that complete excision of pilonidal sinus with primary closure provides good results in terms of healing, morbidity, early return to work and recurrence rate and can be considered the treatment of choice of pilonidal sinus

The femoral hernia: problems in emergency surgery

The femoral hernia can be defined as infrequent, and predominantly found in females, with the highest incidence between 30 and 40 years of age. It shows a high tendency to strangulation, also up to 40% of cases, due to the presence of the Gimbernat ligament, which with its tense fibrous margins, aids strangling known as "raised crest". The diagnosis may not be easy, overall in the clinical presence of acute abdomen in elderly patients, disabled people or people who are uncooperative during physical examination. Therefore, it should be sought with an adequate bilateral exploration of the region in all occlused patients and especially with the use of radiological images of the small intestine. The solution currently practiced is prosthetic, proposed by Lichtenstein, and variously modified by Gilbert, Rutkow, Bendavid, and other which uses a prolene plug in the shape of a cigar, umbrella, or basket, according to the size and characteristics of the parietal defect. In emergency conditions, the technique doesn?t change; but if there is stercorary contamination, it is advisable to use direct repair according to the old method of Bassini. In the last 10 years, we have treated 37 femoral hernias in emergency, using direct repair in only 2 cases. In 3 cases we used PTFE; in the other 32 cases prolene was always used; 20 patients were operated under local anesthetic, 12 under general anesthetic and 5 under peridural anesthetic. Satisfactory results were achieved, with average hospital recovery time of 1.4 days, with an early recovery between 3 and 5 days, with only 2 relapses

Pathophysiological and clinical trials of the abdominal compartment syndrome

The abdominal compartment syndrome (ACS) is defined a situation of high degrade abdominal hypertension (IAH) with clinicals signs of multiorganic dysfunction. It's observed like in the intensive care, in particular surgycals and postraumatics, there is ever a bigger frequence of complications presented by criticals patients. The various trials remark a changeable incidence, but the common factor is characterized by a particular severity of scores. All the possibles mechanicals, haemorragicals, infiammatories, and postraumatics causes act, but don't enable the stability among abdominal content, abdominal compliance and parietal tension. The initial triad of effects is constitued by the elevation of diaphragm and the visceral and vascular compression; after this triad provoke a pathophysiologic system that, through various levels, bring to a respiratory, renal and cardiocirculatory dysfunction and to a parietal, hepatic and intestinal ischemia with consequent bacterical translation: sepsis and MOF. The Burch's classification (1996) report four levels of gravity by the slight (&lt; 15 mmHg) to the heavyest (&gt; 35 mmHg): the firsts two levels are of intensivistic competence and for the detention are used conservatives metodics and pharmacological approach; instead in the lasts two levels it's necessary to foresee a surgycal treatment of laparotomy, washing and drainage with following temporary paret's closure. The mortality is now very elevated (29-62%) especially when it's already established a multiorganical dysfunction; therefore it's necessary forward its appearance through the monitorization of abdominal pression (IAP) with the measurement of vescical pression in alls criticals patients at the aim to treat immediately the firsts signs of IAH

L’ ematoma retroperitoneale post-traumatico

The management of traumatic retroperitoneal haematomas is still a much debated question. Although the diagnosis has become easier using CT with contrast medium, the therapeutic decisions are still difficult because of the great variability of the lesions, which may be simple but very often complicated. Our study is based on 1086 treated patients, 29.5% of the 3682 critical abdominal polytrauma seen in 35 years. Mortality has been 12.9% with a medium ISS (Injury Severity Score) of 23.4. 71.4% of the cases were closed traumas, 28,6% were open traumas. The most common single lesions have been pelvic (43%), followed by the renal traumas (39%). Regarding the associated lesions, the thoracic traumas cause an increment of the ISS score up to 26.2% and of mortality up to 14.6%. The maxillofacial traumas associated with traumatic retroperitoneal haematomas represent 11%, mainly associated with motorcycle accidents, which have increased in the last years from 2,4% in the 70s to 32% these days. Our approach to these patients has been basically conservative. Following the indications obtained by the CT, we widely used interventional angiography, especially for renal lesions and, after pelvic stabilization, for pelvic haematomas. We have chosen surgery considering the kind of traumas (open or closed), the location of the haematoma and especially, the clinical course of the patient's hemodynamic condition