On the Distribution of Quadratic Residues and Non-residues Modulo Composite Integers and Applications to Cryptography

We develop exact formulas for the distribution of quadratic residues and non-residues in sets of the form $a+X=\{(a+x)\bmod n\mid x\in X\}$, where $n$ is a prime or the product of two primes and $X$ is a subset of integers with given Jacobi symbols modulo prime factors of $n$. We then present applications of these formulas to Cocks\u27 identity-based encryption scheme and statistical indistinguishability

Security of Identity-based Encryption Schemes from Quadratic Residues

The aim of this paper is to provide an overview on the newest results regarding the security of identity-based encryption schemes from quadratic residuosity. It is shown that the only secure schemes are the Cocks and Boneh-Gentry-Hamburg schemes (except of anonymous variations of them)

IMPLICA VI. Colaboratorio del Grado en Lenguas, Literaturas y Culturas Románicas

Memoria ID2022-005. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2022-2023

Abdominal Compartment Syndrome – a Surgical Emergency

Over the past six decades, abdominal compartment syndrome (ACS) remained a very controversial subject, both in surgical and non-surgical specialties. Doctors failed to understand why critically ill patients died in the ICU with distended abdomens without fi nding any cause or why postoperative patients with wound defects such as dehiscence died after suturing the wound again „very tightly”. After the concept of intra-abdominal pressure (IAP) was established and methods for measuring it and diagnosing intra-abdominal hypertension (IAH) were available for clinicians to use it, it became clearer that ACS was a very serious and life threating pathology and the need for a correct treatment is essential. In this article we will try to make a literature review of the past decade and see when and how to diagnose correctly a patient with ACS and also how the diagnostic and treatments methods changed over the years

Non-operative management of the sigmoid volvulus – case presentation

Sigmoid volvulus happens when the sigmoid wraps around itself and its mesentery. Sigmoid volvulus accounts for 2% to 50% of all colonic obstructions. This pathology generally affects adults, and it is more common in males. The etiology is multifactorial and controversial; the main symptoms are diffuse abdominal pain, distention and constipation, while the pregnant signs are abdominal distention and tenderness. Laboratory findings are not pathognomonic: abdominal X-ray radiographs show a dilated sigmoid colon and multiple intestinal air-fluid levels, abdominal CT and MRI demonstrate a whirled sigmoid mesentery. Flexible endoscopy reveals a spiral sphincter-like twist of the mucosa. The diagnosis of sigmoid volvulus is established by clinical, radiological, endoscopic, and sometimes operative findings. Although flexible endoscopic detorsion is advocated as the primary treatment choice, emergency surgery is required for patients who present with peritonitis, bowel gangrene, or perforation, or for patients whose non-operative treatment is unsuccessful. Although emergency surgery includes various non-definitive or definitive procedures, resection with primary anastomosis is the most commonly recommended procedure. After a successful non-operative detorsion, elective sigmoid resection and anastomosis is recommended. The overall mortality is 10% to 50%, while the overall morbidity is 6% to 24%

Cholelitiasis in an adult patient with mild hereditary spherocytosis – a case report

Hereditary spherocytosis (HS) is an inherited abnormality of the red blood cell, caused by defects in structural membrane proteins. The condition is dominantly inherited in 75% of people. The severity of the disorder is related to the type and amount of membrane disruption, which is genetically determined. A patient who suffers from this disorder is commonly found in a surgical ward when the disease becomes unmanageable by a hematologist. Surgeons encounter complications such as: jaundice, splenomegaly, gallstone sand severe anemia. We present the case of a 66-year-old woman with a history of hereditary spherocytosis who presented at the emergency room for pain in the right upper quadrant, jaundice and anemia and was diagnosed with gallbladder stones and common bile duct obstruction

Probabilistic functional tractography of the human cortex revisited

In patients with pharmaco-resistant focal epilepsies investigated with intracranial electroencephalography (iEEG), direct electrical stimulations of a cortical region induce cortico-cortical evoked potentials (CCEP) in distant cerebral cortex, which properties can be used to infer large scale brain connectivity. In 2013, we proposed a new probabilistic functional tractography methodology to study human brain connectivity. We have now been revisiting this method in the F-TRACT project (f-tract.eu) by developing a large multicenter CCEP database of several thousand stimulation runs performed in several hundred patients, and associated processing tools to create a probabilistic atlas of human cortico-cortical connections. Here, we wish to present a snapshot of the methods and data of F-TRACT using a pool of 213 epilepsy patients, all studied by stereo-encephalography with intracerebral depth electrodes. The CCEPs were processed using an automated pipeline with the following consecutive steps: detection of each stimulation run from stimulation artifacts in raw intracranial EEG (iEEG) files, bad channels detection with a machine learning approach, model-based stimulation artifact correction, robust averaging over stimulation pulses. Effective connectivity between the stimulated and recording areas is then inferred from the properties of the first CCEP component, i.e. onset and peak latency, amplitude, duration and integral of the significant part. Finally, group statistics of CCEP features are implemented for each brain parcel explored by iEEG electrodes. The localization (coordinates, white/gray matter relative positioning) of electrode contacts were obtained from imaging data (anatomical MRI or CT scans before and after electrodes implantation). The iEEG contacts were repositioned in different brain parcellations from the segmentation of patients' anatomical MRI or from templates in the MNI coordinate system. The F-TRACT database using the first pool of 213 patients provided connectivity probability values for 95% of possible intrahemispheric and 56% of interhemispheric connections and CCEP features for 78% of intrahemisheric and 14% of interhemispheric connections. In this report, we show some examples of anatomo-functional connectivity matrices, and associated directional maps. We also indicate how CCEP features, especially latencies, are related to spatial distances, and allow estimating the velocity distribution of neuronal signals at a large scale. Finally, we describe the impact on the estimated connectivity of the stimulation charge and of the contact localization according to the white or gray matter. The most relevant maps for the scientific community are available for download on f-tract. eu (David et al., 2017) and will be regularly updated during the following months with the addition of more data in the F-TRACT database. This will provide an unprecedented knowledge on the dynamical properties of large fiber tracts in human.Peer reviewe

Risk factors for infections caused by carbapenem-resistant Enterobacterales: an international matched case-control-control study (EURECA)

Cases were patients with complicated urinary tract infection (cUTI), complicated intraabdominal (cIAI), pneumonia or bacteraemia from other sources (BSI-OS) due to CRE; control groups were patients with infection caused by carbapenem-susceptible Enterobacterales (CSE), and by non-infected patients, respectively. Matching criteria included type of infection for CSE group, ward and duration of hospital admission. Conditional logistic regression was used to identify risk factors. Findings Overall, 235 CRE case patients, 235 CSE controls and 705 non-infected controls were included. The CRE infections were cUTI (133, 56.7%), pneumonia (44, 18.7%), cIAI and BSI-OS (29, 12.3% each). Carbapenemase genes were found in 228 isolates: OXA-48/like, 112 (47.6%), KPC, 84 (35.7%), and metallo-beta-lactamases, 44 (18.7%); 13 produced two. The risk factors for CRE infection in both type of controls were (adjusted OR for CSE controls; 95% CI; p value) previous colonisation/infection by CRE (6.94; 2.74-15.53; <0.001), urinary catheter (1.78; 1.03-3.07; 0.038) and exposure to broad spectrum antibiotics, as categorical (2.20; 1.25-3.88; 0.006) and time-dependent (1.04 per day; 1.00-1.07; 0.014); chronic renal failure (2.81; 1.40-5.64; 0.004) and admission from home (0.44; 0.23-0.85; 0.014) were significant only for CSE controls. Subgroup analyses provided similar results. Interpretation The main risk factors for CRE infections in hospitals with high incidence included previous coloni-zation, urinary catheter and exposure to broad spectrum antibiotics

Boneh-Gentry-Hamburg\u27s Identity-based Encryption Schemes Revisited

BasicIBE and AnonIBE are two space-efficient identity-based encryption (IBE) schemes based on quadratic residues, proposed by Boneh, Gentry, and Hamburg, and closely related to Cocks\u27 IBE scheme. BasicIBE is secure in the random oracle model under the quadratic residuosity assumption, while AnonIBE is secure in the standard model under the interactive quadratic residuosity assumption. In this paper we revise the BasicIBE scheme and we show that if the requirements for the deterministic algorithms used to output encryption and decryption polynomials are slightly changed, then the scheme\u27s security margin can be slightly improved