Words and forbidden factors

AbstractGiven a finite or infinite word v, we consider the set M(v) of minimal forbidden factors of v. We show that the set M(v) is of fundamental importance in determining the structure of the word v. In the case of a finite word w we consider two parameters that are related to the size of M(w): the first counts the minimal forbidden factors of w and the second gives the length of the longest minimal forbidden factor of w. We derive sharp upper and lower bounds for both parameters. We prove also that the second parameter is related to the minimal period of the word w. We are further interested to the algorithmic point of view. Indeed, we design linear time algorithm for the following two problems: (i) given w, construct the set M(w) and, conversely, (ii) given M(w), reconstruct the word w. In the case of an infinite word x, we consider the following two functions: gx that counts, for each n, the allowed factors of x of length n and fx that counts, for each n, the minimal forbidden factors of x of length n. We address the following general problem: what information about the structure of x can be derived from the pair (gx,fx)? We prove that these two functions characterize, up to the automorphism exchanging the two letters, the language of factors of each single infinite Sturmian word

Schrödinger’s worker: Are they positive or negative for SARS-CoV-2?

In these days of 2020, tests for the diagnosis of SARS-CoV-2, and their use in the context of health surveillance of workers, are becoming popular. Nevertheless, their sensitivity and specificity could vary on the basis of the type of test used and on the moment of infection of the subject tested. The aim of this viewpoint paper is to make employers, workers, occupational physicians, and public health specialists think about the limits of diagnostic tests currently available, and the possible implication related to the erroneous and incautious assignment of “immunity passports” or “risk-free certificates” to workers during screening campaigns in workplaces

Invariance: a Theoretical Approach for Coding Sets of Words Modulo Literal (Anti)Morphisms

Let $A$ be a finite or countable alphabet and let $\theta$ be literal (anti)morphism onto $A^*$ (by definition, such a correspondence is determinated by a permutation of the alphabet). This paper deals with sets which are invariant under $\theta$ ($\theta$-invariant for short).We establish an extension of the famous defect theorem. Moreover, we prove that for the so-called thin $\theta$-invariant codes, maximality and completeness are two equivalent notions. We prove that a similar property holds in the framework of some special families of $\theta$-invariant codes such as prefix (bifix) codes, codes with a finite deciphering delay, uniformly synchronized codes and circular codes. For a special class of involutive antimorphisms, we prove that any regular $\theta$-invariant code may be embedded into a complete one.Comment: To appear in Acts of WORDS 201

Metformin-associated lactic acidosis and temporary ileostomy: a case report

Lactic acidosis is a well-known complication of the anti-hyperglycemic biguanide agent metformin, especially in peculiar but not rare clinical conditions. Attempts to reduce the incidence of this adverse reaction have been enforced by national agencies over the years. The Italian Medicines Agency recently released a safety recommendation on prescribing the drug and with regard to the existence of several conditions that contraindicate drug continuation, such as dehydration, infection, hypotension, surgery or hyperosmolar contrast agent infusion, but the recommendation does not mention the increased risk related to stoma. The present case report is, to our knowledge, the first in the literature of metformin-associated lactic acidosis in a patient with a recently created ileostomy and low anterior resection for rectal cancer. CASE PRESENTATION: A 70-year-old Caucasian man who had undergone low anterior resection with total mesorectal excision and temporary loop ileostomy creation at our institution returned to our department 30 days later because of nausea, vomiting, diffuse abdominal pain and anuria of about 24 hours' duration. During his physical examination, the patient appeared dehydrated and had tachypnea and a reduced level of consciousness. His laboratory tests showed that he had acute kidney injury and severe lactic acidosis. CONCLUSION: An ileostomy puts patients at high risk for output losses that can lead to dehydration and electrolyte abnormalities. The assessment of the losses through the stoma, especially the ileostomy, should be added to the recommendations issued by pharmacovigilance societies. The present clinical case illustrates the need for clinicians on surgical wards to carefully evaluate patients before resuming metformin therapy and to provide appropriate information at discharge to patients with type 2 diabetes mellitus who have undergone ileostomy. Furthermore, this case report highlights the increasing need for more training of general physicians regarding both surgical and internal medicine problems that may arise in the post-operative course after major surgery in patients with co-morbidities

Evaluation of the burden of HPV-related hospitalizations as a useful tool to increase awareness: 2007–2017 data from the sicilian hospital discharge records

In light of the implementation of human papillomavirus (HPV) prevention strategies, epidemiological studies in different geographical areas are required in order to assess the impact of HPV-related diseases. The purpose of the present study was to describe the burden of HPV-related hospitalizations in Sicily. A retrospective observational study estimated 43,531 hospitalizations attributable to HPV from 2007 to 2017. During the observed period, there was a decrease for all HPV-related conditions with a higher reduction, among neoplasms, for cervical cancer (annual percent change (APC) = −9.9%, p < 0.001). The median age for cervical cancer was 45 years old, with an increasing value from 43 to 47 years (p < 0.001). The age classes with greater decreases in hospital admissions for invasive cancers were women aged 35 years or more (APC range from −5.5 to −9.86) and 25–34 years old (APC = −11.87, p < 0.001) for women with cervical carcinoma in situ. After ten years for vaccine introduction and sixteen years for cervical cancer screening availability, a relatively large decrease in hospital admissions for cervical cancer and other HPV-related diseases in Sicily was observed. Some clinical characteristics of hospitalization, such as increasing age, are suggestive clues for the impact of preventive strategies, but further research is needed to confirm this relationship

Early results of fissurectomy and advancement flap for resistant chronic anal fissure without hypertonia of the internal anal sphincter

The aim of this study was to assess the efficacy of fissurectomy with skin advancement flap in healing chronic anal fissures without hypertonia of the internal anal sphincter. Twenty-six consecutive patients who failed healing after well-practiced topical medical therapy were enrolled. Anorectal manometry was performed preoperative and 6 months postoperatively. All patients were treated with fissurectomy and advancement flap through healthy skin tissue. All patients healed completely within 30 days from operation. The intensity and the duration of pain postdefecation was reduced significantly with respect to the preoperative values starting from the first defecation. One patient suffered urinary retention, two patients suffered infections, and two partial breakdowns were recorded. At 6 months the maximum resting pressure values were similar to those were detected preoperatively. One month after surgery, anal incontinence was reported in seven patients, four of whom complained about it preoperatively. At 12 months, only three subjects reported incontinence. No patients needed reoperation and no recurrences were detected. The fissurectomy, in combination with advancement flap, is a safe sphincter-saving procedure for the treatment of chronic anal fissures without hypertonia of internal anal sphincter that fails medical conservative treatment

Accuracy of Siri and Brozek equations in the percent body fat estimation in older adults

To identify which equation, Siri or Brozek, based on the two compartment model, provides a more accurate conversion of body density (BD) in percent body fat (%BF) in a group of older adults. Cross-sectional study. Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto. 60 older adults, aged 60-92 years. Skinfold thickness was used to estimate BD through Visser et al. prediction equation. The conversion of BD to %BF was done with Siri (%BF-Siri) and Brozek (%BF-Brozek) formulas and these determined values were both compared to Dual-Energy X-ray Absorptiometry (%BF-DXA) evaluations. A strong correlation between the %BF-DXA value and %BF-Siri (r=0.91, p < 0.001) and %BF-Brozek (r=0.91, p < 0.001) was found, although %BF-Siri and %BF-Brozek overestimated %BF-DXA (p < 0.001). The comparison of the %BF-Siri and %BF-Brozek mean values also revealed significant differences (p < 0.001). The %BF-Brozek reflects a better agreement than the %BF-Siri with %BF-DXA with respectively a mean difference of -4.0%BF (limits of agreement = -10.9 to 2.9%) and -5.7%BF (-12.6 to 1.2). The Bland and Altman plots confirmed that %BF-Brozek reflects a better agreement with %BF-DXA. The results of the present study show that the use of Brozek equation may correspond to a more accurate alternative than Siri equation for the conversion of BD in %BF in older adults

Sisters in structure but different in character, some benzaldehyde and cinnamaldehyde derivatives differentially tune Aspergillus flavus secondary metabolism

Great are the expectations for a new generation of antimicrobials, and strenuous are the research efforts towards the exploration of diverse molecular scaffolds—possibly of natural origin – aimed at the synthesis of new compounds against the spread of hazardous fungi. Also high but winding are the paths leading to the definition of biological targets specifically fitting the drug’s structural characteristics. The present study is addressed to inspect differential biological behaviours of cinnamaldehyde and benzaldehyde thiosemicarbazone scaffolds, exploiting the secondary metabolism of the mycotoxigenic phytopathogen Aspergillus flavus. Interestingly, owing to modifications on the parent chemical scaffold, some thiosemicarbazones displayed an increased specificity against one or more developmental processes (conidia germination, aflatoxin biosynthesis, sclerotia production) of A. flavus biology. Through the comparative analysis of results, the ligand-based screening strategy here described has allowed us to delineate which modifications are more promising for distinct purposes: from the control of mycotoxins contamination in food and feed commodities, to the environmental management of microbial pathogens, to the investigation of specific structure–activity features for new generation drug discovery

Transition Property for α\alpha-Power Free Languages with α≥2\alpha\geq 2 and k≥3k\geq 3 Letters

In 1985, Restivo and Salemi presented a list of five problems concerning power free languages. Problem $4$ states: Given $\alpha$-power-free words $u$ and $v$, decide whether there is a transition from $u$ to $v$. Problem $5$ states: Given $\alpha$-power-free words $u$ and $v$, find a transition word $w$, if it exists. Let $\Sigma_k$ denote an alphabet with $k$ letters. Let $L_{k,\alpha}$ denote the $\alpha$-power free language over the alphabet $\Sigma_k$, where $\alpha$ is a rational number or a rational "number with $+$". If $\alpha$ is a "number with $+$" then suppose $k\geq 3$ and $\alpha\geq 2$. If $\alpha$ is "only" a number then suppose $k=3$ and $\alpha>2$ or $k>3$ and $\alpha\geq 2$. We show that: If $u\in L_{k,\alpha}$ is a right extendable word in $L_{k,\alpha}$ and $v\in L_{k,\alpha}$ is a left extendable word in $L_{k,\alpha}$ then there is a (transition) word $w$ such that $uwv\in L_{k,\alpha}$. We also show a construction of the word $w$