2,367 research outputs found
Origin and Control Strategies of Biofilms in the Cultural Heritage
Biodeterioration is defined as the undesirable change in the properties of materials caused by the activity of biological agents. This process is complex and involves alterations in the physicochemical and mechanical properties by the action of organisms and depends on the microorganisms involved, type of substrate, and environmental conditions. The biodeterioration of cultural heritage is the physical or chemical damage caused by microorganisms on objects, monuments, or buildings that belong to the cultural heritage. Among the main materials that can be affected are: stone, metal, ceramic, polymers, and other materials. Among the main undesirable effects to these materials are: discoloration, dissolution, rupture, and efflorescence among others. Biofilms represent the usual form of growth of bacteria and consist of communities of microorganisms that grow attached to an inert surface or a living tissue, surrounded by an extracellular matrix that they themselves synthesize. The importance of biodeterioration by biofilms is mainly related to changes in pH values, ionic concentrations, oxide-reduction reactions in the biofilm thickness, and in the interface with the substrate and enzymatic degradation. This chapter presents evidence of the participation of biofilms and associated mechanisms in biodeterioration as well as the main prevention and control strategies
A Stomach Bug? Not What You May Think: A Case of Post-Viral Gastroparesis Caused by SARS-CoV-2
Gastroparesis has a wide range of etiologies including diabetes, medications, post-surgical, post-viral and idiopathic (1). SARS-CoV-2 can cause gastrointestinal symptoms which typically resolve within the first few weeks of infection (2). However, some sequelae persist beyond the initial infectious period
Degeneracy in excited state quantum phase transitions of two-level bosonic models and its influence on system dynamics
Excited state quantum phase transitions in collective many-body quantum
systems influence the system spectral properties due to changing degeneracy
patterns in different phases. We report a fundamental difference in the nature
of the degeneracy for boson two-level models, depending on the dimension of the
space where the models were defined. To illustrate the consequences, we assess
the validity of an out-of-time-order correlator as a possible order operator
for excited state quantum phase transitions in different models
Non-supersymmetric heterotic model building
We investigate orbifold and smooth Calabi-Yau compactifications of the
non-supersymmetric heterotic SO(16)xSO(16) string. We focus on such Calabi-Yau
backgrounds in order to recycle commonly employed techniques, like index
theorems and cohomology theory, to determine both the fermionic and bosonic 4D
spectra. We argue that the N=0 theory never leads to tachyons on smooth
Calabi-Yaus in the large volume approximation. As twisted tachyons may arise on
certain singular orbifolds, we conjecture that such tachyonic states are lifted
in the full blow-up. We perform model searches on selected orbifold geometries.
In particular, we construct an explicit example of a Standard Model-like theory
with three generations and a single Higgs field.Comment: 1+30 pages latex, 11 tables; v2: references and minor revisions
added, matches version published in JHE
DIVERSIDAD GENÉTICA DEL VIRUS DE INMUNODEFICIENCIA
El Síndrome de Inmunodeficiencia Adquirida (SIDA), es considerado como una pandemia que al igual que otras enfermedades requiere del diagnóstico, vigilancia y tratamiento efectivos. En México como en el resto de los países del mundo, el SIDA es considerado como un serio problema de salud pública, ya que a pesar de todos los esfuerzos que se han hecho para difundir los conocimientos de los aspectos epidemiológicos, de diagnóstico, tratamiento y prevención, el número de casos reales es mayor que el informado por las autoridades; por lo tanto, las consecuencias socioeconómicas son mucho más graves. El VIH-1, es un virus que experimenta una alta variación genética, ésta, causa cambios en el tropismo, virulencia y transmisión de la infección. Nuevas variantes y/o subtipos del VIH-1 se encuentran circulando con un amplio rango de propiedades de virulencia y transmisión que están surgiendo y dispersándose alrededor del mundo en una forma alarmante. El VIH-1 predominante en México es el subtipo B, pero esto no excluye la presencia de otros subtipos en el país, como es la presencia del Subtipo C detectado en un individuo sudafricano. Una adecuada vigilancia epidemiológica del VIH/SIDA incluyendo la identificación, caracterización y análisis de los subtipos predominantes en nuestro país deben ser llevadas a cabo en un esfuerzo para evaluar su diversidad genética y comprender mejor la problemática sobre su diseminación, definir los patrones de distribución geográfica, su epidemiología, sobre el desarrollo de antivirales y sobre todo el diseño de vacunas.Palabras clave: SIDA, VIH, subtipos y formas recombinantes circulantes (FRC). AIDS, HIV, subtypes and Circulating Recombinant Forms(CRF
Obscuration beyond the nucleus: infrared quasars can be buried in extreme compact starbursts
In the standard quasar model, the accretion disk obscuration is due to the
canonical dusty torus. Here, we argue that a substantial part of the quasar
obscuration can come from the interstellar medium (ISM) when the quasars are
embedded in compact starbursts. We use an obscuration-unbiased sample of 578
infrared (IR) quasars at and archival ALMA submillimeter host
galaxy sizes to investigate the ISM contribution to the quasar obscuration. We
calculate SFR and ISM column densities for the IR quasars and a control sample
of submillimeter galaxies (SMGs) not hosting quasar activity and show that: (1)
the quasar obscured fraction is constant up to , and then increases towards higher SFR, suggesting that the ISM
obscuration plays a significant role in starburst host galaxies, and (2) at
, the SMGs and IR quasars have
similarly compact submillimeter sizes () and,
consequently, the ISM can heavily obscure the quasar, even reaching
Compton-thick () levels in extreme cases.
Based on our results, we infer that of the IR quasars with
are obscured solely by the ISM.Comment: Accepted for publication in MNRAS Letter
The Effect of a Physical Activity Program on the Total Number of Primary Care Visits in Inactive Patients: A 15-Month Randomized Controlled Trial
Abstract
Background: Effective promotion of exercise could result in substantial savings in healthcare cost expenses in terms of
direct medical costs, such as the number of medical appointments. However, this is hampered by our limited knowledge of
how to achieve sustained increases in physical activity.
Objectives: To assess the effectiveness of a Primary Health Care (PHC) based physical activity program in reducing the total
number of visits to the healthcare center among inactive patients, over a 15-month period.
Research Design: Randomized controlled trial.
Subjects: Three hundred and sixty-two (n = 362) inactive patients suffering from at least one chronic condition were
included. One hundred and eighty-three patients (n = 183; mean (SD); 68.3 (8.8) years; 118 women) were randomly allocated
to the physical activity program (IG). One hundred and seventy-nine patients (n = 179; 67.2 (9.1) years; 106 women) were
allocated to the control group (CG). The IG went through a three-month standardized physical activity program led by
physical activity specialists and linked to community resources.
Measures: The total number of medical appointments to the PHC, during twelve months before and after the program, was
registered. Self-reported health status (SF-12 version 2) was assessed at baseline (month 0), at the end of the intervention
(month 3), and at 12 months follow-up after the end of the intervention (month 15).
Results: The IG had a significantly reduced number of visits during the 12 months after the intervention: 14.8 (8.5). The CG
remained about the same: 18.2 (11.1) (P = .002).
Conclusions: Our findings indicate that a 3-month physical activity program linked to community resources is a shortduration,
effective and sustainable intervention in inactive patients to decrease rates of PHC visits.
Trial Registration: ClinicalTrials.gov NCT0071483
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