The forward kinematics of doubly-planar Gough-Stewart platforms and the position analysis of strips of tetrahedra

The final publication is available at link.springer.comA strip of tetrahedra is a tetrahedron-tetrahedron truss where any tetrahedron has two neighbors except those in the extremes which have only one. The problem of finding all the possible lengths for an edge in the strip compatible with a given distance imposed between the strip end-points has been revealed of relevance due to the large number of possible applications. In this paper, this is applied to solve the forward kinematics of 6-6 Gough-Stewart platforms with planar base and moving platform, a problem which is known to have up to 40 solutions (20 if we do not consider mirror configurations with respect to the base as different solutions).Peer ReviewedPostprint (author's final draft

A Primer on Resonances in Quantum Mechanics

After a pedagogical introduction to the concept of resonance in classical and quantum mechanics, some interesting applications are discussed. The subject includes resonances occurring as one of the effects of radiative reaction, the resonances involved in the refraction of electromagnetic waves by a medium with a complex refractive index, and quantum decaying systems described in terms of resonant states of the energy. Some useful mathematical approaches like the Fourier transform, the complex scaling method and the Darboux transformation are also reviewed.Comment: 28 pages, 9 figures, lectures presented at the Advanced Summer School in Physics 2008, Cinvestav, Mexic

Infected pancreatic necrosis: outcomes and clinical predictors of mortality. A post hoc analysis of the MANCTRA-1 international study

: The identification of high-risk patients in the early stages of infected pancreatic necrosis (IPN) is critical, because it could help the clinicians to adopt more effective management strategies. We conducted a post hoc analysis of the MANCTRA-1 international study to assess the association between clinical risk factors and mortality among adult patients with IPN. Univariable and multivariable logistic regression models were used to identify prognostic factors of mortality. We identified 247 consecutive patients with IPN hospitalised between January 2019 and December 2020. History of uncontrolled arterial hypertension (p = 0.032; 95% CI 1.135-15.882; aOR 4.245), qSOFA (p = 0.005; 95% CI 1.359-5.879; aOR 2.828), renal failure (p = 0.022; 95% CI 1.138-5.442; aOR 2.489), and haemodynamic failure (p = 0.018; 95% CI 1.184-5.978; aOR 2.661), were identified as independent predictors of mortality in IPN patients. Cholangitis (p = 0.003; 95% CI 1.598-9.930; aOR 3.983), abdominal compartment syndrome (p = 0.032; 95% CI 1.090-6.967; aOR 2.735), and gastrointestinal/intra-abdominal bleeding (p = 0.009; 95% CI 1.286-5.712; aOR 2.710) were independently associated with the risk of mortality. Upfront open surgical necrosectomy was strongly associated with the risk of mortality (p < 0.001; 95% CI 1.912-7.442; aOR 3.772), whereas endoscopic drainage of pancreatic necrosis (p = 0.018; 95% CI 0.138-0.834; aOR 0.339) and enteral nutrition (p = 0.003; 95% CI 0.143-0.716; aOR 0.320) were found as protective factors. Organ failure, acute cholangitis, and upfront open surgical necrosectomy were the most significant predictors of mortality. Our study confirmed that, even in a subgroup of particularly ill patients such as those with IPN, upfront open surgery should be avoided as much as possible. Study protocol registered in ClinicalTrials.Gov (I.D. Number NCT04747990)

Closed-form solution to the position analysis of Watt–Baranov trusses using the bilateration method

The exact position analysis of a planar mechanism reduces to compute the roots of its characteristic polynomial. Obtaining this polynomial almost invariably involves, as a first step, obtaining a system of equations derived from the independent kinematic loops of the mechanism. The use of kinematic loops to this end has seldom been questioned despite deriving the characteristic polynomial from them requires complex variable eliminations and, in most cases, trigonometric substitutions. As an alternative, the bilateration method has recently been used to obtain the characteristic polynomials of the three-loop Baranov trusses without relying on variable eliminations nor trigonometric substitutions and using no other tools than elementary algebra. This paper shows how this technique can be applied to members of a family of Baranov trusses resulting from the circular concatenation of the Watt mechanism irrespective of the resulting number of kinematic loops. To our knowledge, this is the first time that the characteristic polynomial of a Baranov truss with more that five loops has been obtained, and hence, its position analysis solved in closed form

Por Don Nicolas Chirinos Escalante, hijo, y heredero de D. Diego Chirinos, y de Doña Ana Lozano difuntos, vezino de la Ciudad de Tarifa. contra Doña Petronila de Ortega, como madre, tutora, y curadora de su hijo ... Sobre : la possesion de los bienes ,

A 109/092(40

Inorganic Polyphosphate Affects Biofilm Assembly, Capsule Formation, and Virulence of Hypervirulent ST23 Klebsiella pneumoniae

The emergence of hypervirulent Klebsiella pneumoniae (hvKP) strains poses a significant threat to public health due to high mortality rates and propensity to cause severe community-acquired infections in healthy individuals. The ability to form biofilms and produce a protective capsule contributes to its enhanced virulence and is a significant challenge to effective antibiotic treatment. Polyphosphate kinase 1 (PPK1) is an enzyme responsible for inorganic polyphosphate synthesis and plays a vital role in regulating various physiological processes in bacteria. In this study, we investigated the impact of polyP metabolism on the biofilm and capsule formation and virulence traits in hvKP using Dictyostelium discoideum amoeba as a model host. We found that the PPK1 null mutant was impaired in biofilm and capsule formation and showed attenuated virulence in D. discoideum compared to the wild-type strain. We performed a proteomic analysis to gain further insights into the underlying molecular mechanism. The results revealed that the PPK1 mutant had a differential expression of proteins involved in capsule synthesis (Wzi-Ugd), biofilm formation (MrkC-D-H), synthesis of the colibactin genotoxin precursor (ClbB), as well as proteins associated with the synthesis and modification of lipid A (ArnB-LpxC-PagP). These proteomic findings corroborate the phenotypic observations and indicate that the PPK1 mutation is associated with impaired biofilm and capsule formation and attenuated virulence in hvKP. Overall, our study highlights the importance of polyP synthesis in regulating extracellular biomolecules and virulence in K. pneumoniae and provides insights into potential therapeutic targets for treating K. pneumoniae infections

Timing of Cholecystectomy After Moderate and Severe Acute Biliary Pancreatitis

IMPORTANCE Considering the lack of equipoise regarding the timing of cholecystectomy in patients with moderately severe and severe acute biliary pancreatitis (ABP), it is critical to assess this issue.OBJECTIVE To assess the outcomes of early cholecystectomy (EC) in patients with moderately severe and severe ABP.DESIGN, SETTINGS, AND PARTICIPANTS This cohort study retrospectively analyzed real-life data from the MANCTRA-1 (Compliance With Evidence-Based Clinical Guidelines in the Management of Acute Biliary Pancreatitis) data set, assessing 5304 consecutive patients hospitalized between January 1, 2019, and December 31, 2020, for ABP from 42 countries. A total of 3696 patients who were hospitalized for ABP and underwent cholecystectomy were included in the analysis; of these, 1202 underwent EC, defined as a cholecystectomy performed within 14 days of admission. Univariable and multivariable logistic regression models were used to identify prognostic factors of mortality and morbidity. Data analysis was performed from January to February 2023.MAIN OUTCOMES Mortality and morbidity after EC.RESULTS Of the 3696 patients (mean [SD] age, 58.5 [17.8] years; 1907 [51.5%] female) included in the analysis, 1202 (32.5%) underwent EC and 2494 (67.5%) underwent delayed cholecystectomy (DC). Overall, EC presented an increased risk of postoperative mortality (1.4% vs 0.1%, P <.001) and morbidity (7.7% vs 3.7%, P < .001) compared with DC. On the multivariable analysis, moderately severe and severe ABP were associated with increased mortality (odds ratio [OR], 361.46; 95% CI, 2.28-57 212.31; P = .02) and morbidity (OR, 2.64; 95% CI, 1.35-5.19; P = .005). In patients with moderately severe and severe ABP (n = 108), EC was associated with an increased risk of mortality (16 [15.6%] vs 0 [0%], P < .001), morbidity (30 [30.3%] vs 57 [5.5%], P < .001), bile leakage (2 [2.4%] vs 4 [0.4%], P = .02), and infections (12 [14.6%] vs 4 [0.4%], P < .001) compared with patients with mild ABP who underwent EC. In patients with moderately severe and severe ABP (n = 108), EC was associated with higher mortality (16 [15.6%] vs 2 [1.2%], P < .001), morbidity (30 [30.3%] vs 17 [10.3%], P < .001), and infections (12 [14.6%] vs 2 [1.3%], P < .001) compared with patients with moderately severe and severe ABP who underwent DC. On the multivariable analysis, the patient's age (OR, 1.12; 95% CI, 1.02-1.36; P = .03) and American Society of Anesthesiologists score (OR, 5.91; 95% CI, 1.06-32.78; P = .04) were associated with mortality; severe complications of ABP were associated with increased mortality (OR, 50.04; 95% CI, 2.37-1058.01; P = .01) and morbidity (OR, 33.64; 95% CI, 3.19-354.73; P = .003).CONCLUSIONS AND RELEVANCE This cohort study's findings suggest that EC should be considered carefully in patients with moderately severe and severe ABP, as it was associated with increased postoperative mortality and morbidity. However, older and more fragile patients manifesting severe complications related to ABP should most likely not be considered for EC