1000 resultados para topologia algebrica superfici varietà 3-varietà presentazione poliedro poligono coomologia dualità


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La percezione coerente del mondo esterno è basata sull'integrazione della grande varietà di input provenienti dalle differenti modalità sensoriali. Il processo di elaborazione delle diverse informazioni recepite, fin dalle prime fasi, è caratterizzato da meccanismi ancora in fase di studio, che, però, possono essere rilevati tramite l’utilizzo di modelli computazionali basati su una rete neurale specifica. In questa Tesi si è preso in considerazione il modello neurale elaborato per simulare gli aspetti spaziali e temporali di illusioni audiovisive, quali l’effetto ventriloquismo e la fission illusion, in modo da poter svolgere un’analisi computazionale del ventriloquismo temporale. Il principale effetto di questo fenomeno consiste nello spostamento dell’istante di occorrenza di uno stimolo visivo verso quello di un segnale acustico presentato in prossimità temporale. Il modello, basato principalmente sul fatto che i neuroni visivi e uditivi comunicano tramite sinapsi eccitatorie e che i campi recettivi spazio-temporali sono differenti per le due modalità sensoriali, è in grado di riprodurre i principali effetti dell’integrazione temporale tra gli stimoli, dando luogo all'effetto illusorio. Si è adattato il modello in modo da rilevare, quantificare e misurare l’estensione del ventriloquismo temporale per diverse disposizioni spaziali e temporali di presentazione degli stimoli. L’analisi è stata ripetuta variando i principali parametri, in modo da rilevare la sensibilità del modello e, quindi, fare valutazioni sui fattori particolarmente influenzanti il fenomeno, confrontando poi i risultati con i dati in letteratura.

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Introduzione: La presentazione podalica complica il 3-4% delle gravidanze singole a termine. Sebbene il parto vaginale sia possibile, gli studi in letteratura hanno riportato un aumento del rischio di mortalità e morbilità fetale. Di conseguenza nel mondo il numero di tagli cesarei eseguiti per presentazione podalica è alto. Il rivolgimento per manovre esterne (RME) è una procedura ostetrica sicura che permette il passaggio del feto dalla presentazione podalica a quella cefalica, riducendo il numero dei tagli cesarei. L’angolo di progressione della parte presentata (AoP) è un parametro ecografico descritto in letteratura per la valutazione della progressione della parte presentata attraverso il canale del parto ed è stato recentemente studiato nelle gravidanze con presentazione podalica del feto. Obiettivi: L’obiettivo primario è valutare la correlazione tra l’AoP e il successo del RME. L’obiettivo secondario è verificare se esiste correlazione tra parametri anamnestici ed ecografici e la riuscita del RME. Materiali e metodi: È stato condotto uno studio osservazione prospettico monocentrico, sono state reclutate previo consenso informato 54 pazienti afferenti presso l’Ospedale Maggiore di Bologna con gravidanza singola dopo le 36 settimane e feto in presentazione podalica tra gennaio 2020 e giugno 2023. Risultati: La percentuale di RME riusciti è stata del 48,2%, il 53,7% delle donne ha partorito mediante taglio cesareo. Non abbiamo trovato una correlazione tra AoP e successo del rivolgimento. Tra le altre variabili analizzate l’unica correlata al successo del RME è la quantità di liquido amniotico Conclusioni: Non abbiamo trovato una correlazione tra AOP e successo del RME. Come descritto in letteratura l’unico parametro ecografico che è risultato associato al successo del RME è la quantità di liquido amniotico. Dato il disegno dello studio e la scarsa numerosità del campione sono necessari ulteriori studi per confermare i risultati.

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In questa tesi vengono studiati anelli commutativi unitari in cui ogni catena ascentente o ogni catena discendente di ideali diventa stazionaria dopo un numero finito di passi. Un anello commutativo unitario R in cui vale la condizione della catena ascendente, ossia ogni catena ascendente di ideali a_1 ⊆ a_2 ⊆ · · · ⊆ R diventa stazionaria dopo un numero finito di passi, o, equivalentemente, in cui ogni ideale è generato da un numero finito di elementi, si dice noetheriano. Questa classe di anelli deve il proprio nome alla matematica tedesca Emmy Noether che, nel 1921, studiando un famoso risultato di Lasker per ideali di anelli di polinomi, si accorse che esso valeva in tutti gli anelli in cui gli ideali sono finitamente generati. Questi anelli giocano un ruolo importante in geometria algebrica, in quanto le varietà algebriche sono luoghi di zeri di polinomi in più variabili a coefficienti in un campo K e le proprietà degli ideali dell’anello K[x_1, . . . , x_n] si riflettono nelle proprietà delle varietà algebriche di K^n. Inoltre, per questi anelli esistono procedure algoritmiche che sono possibili proprio grazie alla condizione della catena ascendente. Un anello commutativo unitario R in cui vale la condizione della catena discendente, ossia ogni ogni catena discendente di ideali . . . a_2 ⊆ a_1 ⊆ R diventa stazionaria dopo un numero finito di passi, si dice artiniano, dal nome del matematico austriaco Emil Artin che li introdusse e ne studiò le proprietà. Il Teorema di Akizuki afferma che un anello commutativo unitario R è artiniano se e solo se è noetheriano di dimensione zero, ossia ogni suo ideale primo è massimale.

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Background: Il pectus excavatum (EP) è l'anomalia congenita più comune della parete toracica. È caratterizzato da depressione variabile dello sterno e cartilagini costali inferiori. I pazienti con EP possono presentare molti sintomi diversi. Alcuni pazienti con EP soffrono di limitazioni funzionali, problematiche posturali e psicosociali legate all’immagine corporea. Tuttavia, i vari interventi non sono stati standardizzati. Obiettivi: Questa scoping review mira a mappare e sintetizzare la letteratura con lo scopo di identificare gli interventi riabilitativi presenti per adolescenti e bambini con pectus excavatum. Metodi: La ricerca, terminata ad agosto 2022, è stata effettuata nelle seguenti banche dati: PUBMED, Cochrane Library e PEDro. È stato inoltre utilizzato il motore di ricerca Google Scholar per contenuti della letteratura grigia. La selezione degli studi è avvenuta secondo precisi criteri di inclusione; sono stati considerati sia studi primari che secondari senza limiti geografici e di lingua. I risultati sono stati presentati sia in modalità numerica sia tematica. Risultati: Da 47 articoli iniziali, sono stati selezionati 30 articoli, di cui 8 systematic review, 5 RCT, 3 case reports, 2 preliminary reports, 6 studi retrospettivi, 1 case series, 2 studi primari diagnostici, 1 studio prospettico e 2 records dalla letteratura grigia. Il processo di selezione degli articoli è stato riportato attraverso il diagramma di flusso, mentre i contenuti dei singoli articoli sono stati schematizzati in una tabella sinottica. Conclusioni: Dall’analisi attuale della letteratura emerge che, nonostante la varietà dei trattamenti presenti negli articoli, rimane un’evidente lacuna sull’unanimità riguardo alle indicazioni e alle linee guida da seguire nell’approccio e intervento riabilitativo del ragazzo con diagnosi di pectus excavatum. Questa scoping review può rappresentare un punto di partenza per le future ricerche.

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Although various abutment connections and materials have recently been introduced, insufficient data exist regarding the effect of stress distribution on their mechanical performance. The purpose of this study was to investigate the effect of different abutment materials and platform connections on stress distribution in single anterior implant-supported restorations with the finite element method. Nine experimental groups were modeled from the combination of 3 platform connections (external hexagon, internal hexagon, and Morse tapered) and 3 abutment materials (titanium, zirconia, and hybrid) as follows: external hexagon-titanium, external hexagon-zirconia, external hexagon-hybrid, internal hexagon-titanium, internal hexagon-zirconia, internal hexagon-hybrid, Morse tapered-titanium, Morse tapered-zirconia, and Morse tapered-hybrid. Finite element models consisted of a 4×13-mm implant, anatomic abutment, and lithium disilicate central incisor crown cemented over the abutment. The 49 N occlusal loading was applied in 6 steps to simulate the incisal guidance. Equivalent von Mises stress (σvM) was used for both the qualitative and quantitative evaluation of the implant and abutment in all the groups and the maximum (σmax) and minimum (σmin) principal stresses for the numerical comparison of the zirconia parts. The highest abutment σvM occurred in the Morse-tapered groups and the lowest in the external hexagon-hybrid, internal hexagon-titanium, and internal hexagon-hybrid groups. The σmax and σmin values were lower in the hybrid groups than in the zirconia groups. The stress distribution concentrated in the abutment-implant interface in all the groups, regardless of the platform connection or abutment material. The platform connection influenced the stress on abutments more than the abutment material. The stress values for implants were similar among different platform connections, but greater stress concentrations were observed in internal connections.

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Twelve novel 8-hydroxyquinoline derivatives were synthesized with good yields by performing copper-catalyzed Huisgen 1,3-dipolar cycloaddition (click reaction) between an 8-O-alkylated-quinoline containing a terminal alkyne and various aromatic or protected sugar azides. These compounds were evaluated in vitro for their antiproliferative activity on various cancer cell types. Protected sugar derivative 16 was the most active compound in the series, exhibiting potent antiproliferative activity and high selectivity toward ovarian cancer cells (OVCAR-03, GI50 < 0.25 μg mL(-1)); this derivative was more active than the reference drug doxorubicin (OVCAR-03, GI50 = 0.43 μg mL(-1)). In structure-activity relationship (SAR) studies, the physico-chemical parameters of the compounds were evaluated and docking calculations were performed for the α-glucosidase active site to predict the possible mechanism of action of this series of compounds.

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A new enantioselective Heck-Matsuda desymmetrization reaction was accomplished by using 3-cyclopentenol to produce chiral five-membered 4-aryl cyclopentenol scaffolds in good yields and high ee's, together with some 3-aryl-cyclopentanones as minor products. Mechanistically, the hydroxyl group of 3-cyclopentenol acts as a directing group and is responsible for the cis- arrangement in the formation of the 4-aryl-cyclopentenols.

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Bisphenol A (BPA) is a chemical that has been investigated for it potential to cause prostate diseases. In this study, pregnant Sprague-Dawley rats were treated with 25 or 250 μg/kg BPA from gestational day (GD) 10 to GD21 with or without concurrent indole-3-carbinol (I3C) feeding. I3C is a phytochemical, and it affords chemoprotection against many types of neoplasia. Male F1 rats from different litters were euthanized on post-natal day (PND) 21 and PND180. BPA-treated groups showed a significant increase in histopathological lesions, but I3C feeding reversed many of these changes, mainly at PND180. Maternal I3C feeding increased prostate epithelial apoptosis in the BPA-treated groups and across age groups. Furthermore, I3C induced partial normalization of the prostate histoarchitecture. The results pointed to a protective effect of maternal I3C feeding during pregnancy in the BPA-exposed male offspring, thereby indicating reduction in the harmful effects of gestational BPA imprinting on the prostate.

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In the title compound, C17H15NO4, the conformation about the C=C double bond [1.348 (2) Å] is E with the ketone group almost co-planar [C-C-C-C torsion angle = 7.2 (2)°] but the phenyl group twisted away [C-C-C-C = 160.93 (17)°]. The terminal aromatic rings are almost perpendicular to each other [dihedral angle = 81.61 (9)°] giving the mol-ecule an overall U-shape. The crystal packing feature benzene-C-H⋯O(ketone) contacts that lead to supra-molecular helical chains along the b axis. These are connected by π-π inter-actions between benzene and phenyl rings [inter-centroid distance = 3.6648 (14) Å], resulting in the formation of a supra-molecular layer in the bc plane.

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In the title compound, C17H14N2O6, the conformation about the C=C double bond [1.345 (2) Å] is E, with the ketone moiety almost coplanar [C-C-C-C torsion angle = 9.5 (2)°] along with the phenyl ring [C-C-C-C = 5.9 (2)°]. The aromatic rings are almost perpendicular to each other [dihedral angle = 86.66 (7)°]. The 4-nitro moiety is approximately coplanar with the benzene ring to which it is attached [O-N-C-C = 4.2 (2)°], whereas the one in the ortho position is twisted [O-N-C-C = 138.28 (13)°]. The mol-ecules associate via C-H⋯O inter-actions, involving both O atoms from the 2-nitro group, to form a helical supra-molecular chain along [010]. Nitro-nitro N⋯O inter-actions [2.8461 (19) Å] connect the chains into layers that stack along [001].

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Galectin-3 (gal-3) is a β-galactoside binding protein related to many tumoral aspects, e.g. angiogenesis, cell growth and motility and resistance to cell death. Evidence has shown its upregulation upon hypoxia, a common feature in solid tumors such as glioblastoma multiformes (GBM). This tumor presents a unique feature described as pseudopalisading cells, which accumulate large amounts of gal-3. Tumor cells far from hypoxic/nutrient deprived areas express little, if any gal-3. Here, we have shown that the hybrid glioma cell line, NG97ht, recapitulates GBM growth forming gal-3 positive pseudopalisades even when cells are grafted subcutaneously in nude mice. In vitro experiments were performed exposing these cells to conditions mimicking tumor areas that display oxygen and nutrient deprivation. Results indicated that gal-3 transcription under hypoxic conditions requires previous protein synthesis and is triggered in a HIF-1α and NF-κB dependent manner. In addition, a significant proportion of cells die only when exposed simultaneously to hypoxia and nutrient deprivation and demonstrate ROS induction. Inhibition of gal-3 expression using siRNA led to protein knockdown followed by a 1.7-2.2 fold increase in cell death. Similar results were also found in a human GBM cell line, T98G. In vivo, U87MG gal-3 knockdown cells inoculated subcutaneously in nude mice demonstrated decreased tumor growth and increased time for tumor engraftment. These results indicate that gal-3 protected cells from cell death under hypoxia and nutrient deprivation in vitro and that gal-3 is a key factor in tumor growth and engraftment in hypoxic and nutrient-deprived microenvironments. Overexpression of gal-3, thus, is part of an adaptive program leading to tumor cell survival under these stressing conditions.

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A series of novel 1-(substituted phenyl)-3-(2-oxo-1,3,4-oxadiazol-5-yl) β-carbolines (4a-e) and the corresponding Mannich bases 5-9(a-c) were synthesized and evaluated for their in vitro antitumor activity against seven human cancer cell lines. Compounds of 4a-e series showed a broad spectrum of antitumor activity, with GI50 values lower than 15μM for five cell lines. The derivative 4b, having the N,N-dimethylaminophenyl group at C-1, displayed the highest activity with GI50 in the range of 0.67-3.20μM. A high selectivity and potent activity were observed for some Mannich bases, particularly towards resistant ovarian (NCI-ADR/RES) cell lines (5a, 5b, 6a, 6c and 9b), and ovarian (OVCAR-03) cell lines (5b, 6a, 6c, 9a, 9b and 9c). In addition, the interaction of compound 4b with DNA was investigated by using UV and fluorescence spectroscopic analysis. These studies indicated that 4b interact with ctDNA by intercalation binding.

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Mutations in the FGFR3 gene cause the phenotypic spectrum of FGFR3 chondrodysplasias ranging from lethal forms to the milder phenotype seen in hypochondroplasia (Hch). The p.N540K mutation in the FGFR3 gene occurs in ∼70% of individuals with Hch, and nearly 30% of individuals with the Hch phenotype have no mutations in the FGFR3, which suggests genetic heterogeneity. The identification of a severe case of Hch associated with the typical mutation c.1620C > A and the occurrence of a c.1150T > C change that resulted in a p.F384L in exon 10, together with the suspicion that this second change could be a modulator of the phenotype, prompted us to investigate this hypothesis in a cohort of patients. An analysis of 48 patients with FGFR3 chondrodysplasia phenotypes and 330 healthy (control) individuals revealed no significant difference in the frequency of the C allele at the c.1150 position (p = 0.34). One patient carrying the combination `pathogenic mutation plus the allelic variant c.1150T > C' had a typical achondroplasia (Ach) phenotype. In addition, three other patients with atypical phenotypes showed no association with the allelic variant. Together, these results do not support the hypothesis of a modulatory role for the c.1150T > C change in the FGFR3 gene.

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Maxillofacial trauma resulting from falls in elderly patients is a major social and health care concern. Most of these traumatic events involve mandibular fractures. The aim of this study was to analyze stress distributions from traumatic loads applied on the symphyseal, parasymphyseal, and mandibular body regions in the elderly edentulous mandible using finite-element analysis (FEA). Computerized tomographic analysis of an edentulous macerated human mandible of a patient approximately 65 years old was performed. The bone structure was converted into a 3-dimensional stereolithographic model, which was used to construct the computer-aided design (CAD) geometry for FEA. The mechanical properties of cortical and cancellous bone were characterized as isotropic and elastic structures, respectively, in the CAD model. The condyles were constrained to prevent free movement in the x-, y-, and z-axes during simulation. This enabled the simulation to include the presence of masticatory muscles during trauma. Three different simulations were performed. Loads of 700 N were applied perpendicular to the surface of the cortical bone in the symphyseal, parasymphyseal, and mandibular body regions. The simulation results were evaluated according to equivalent von Mises stress distributions. Traumatic load at the symphyseal region generated low stress levels in the mental region and high stress levels in the mandibular neck. Traumatic load at the parasymphyseal region concentrated the resulting stress close to the mental foramen. Traumatic load in the mandibular body generated extensive stress in the mandibular body, angle, and ramus. FEA enabled precise mapping of the stress distribution in a human elderly edentulous mandible (neck and mandibular angle) in response to 3 different traumatic load conditions. This knowledge can help guide emergency responders as they evaluate patients after a traumatic event.

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The main aim of this investigation was to verify the relationship of the variables measured during a 3-minute all-out test with aerobic (i.e., peak oxygen uptake [(Equation is included in full-text article.)] and intensity corresponding to the lactate minimum [LMI]) and anaerobic parameters (i.e., anaerobic work) measured during a 400-m maximal performance. To measure force continually and to avoid the possible influences caused by turns, the 3-minute all-out effort was performed in tethered swimming. Thirty swimmers performed the following tests: (a) a 3-minute all-out tethered swimming test to determine the final force (equivalent to critical force: CF3-MIN) and the work performed above CF3-MIN (W'3-MIN), (b) a LMI protocol to determine the LMI during front crawl swimming, and (c) a 400-m maximal test to determine the (Equation is included in full-text article.)and total anaerobic contribution (WANA). Correlations between the variables were tested using the Pearson's correlation test (p ≤ 0.05). CF3-MIN (73.9 ± 13.2 N) presented a high correlation with the LMI (1.33 ± 0.08 m·s; p = 0.01) and (Equation is included in full-text article.)(4.5 ± 1.2 L·min; p = 0.01). However, the W'3-MIN (1,943.2 ± 719.2 N·s) was only moderately correlated with LMI (p = 0.02) and (Equation is included in full-text article.)(p = 0.01). In summary, CF3-MIN determined during the 3-minute all-out effort is associated with oxidative metabolism and can be used to estimate the aerobic capacity of swimmers. In contrast, the anaerobic component of this model (W'3-MIN) is not correlated with WANA.