We propose a new type of concrete for the attenuation of elastic waves induced by dynamic excitation. In this metamaterial, which we call metaconcrete, the stone, sand, and gravel aggregates of ...standard concrete are replaced with spherical inclusions consisting of a heavy metal core coated with a soft outer layer. These engineered aggregates can be tuned so that particular frequencies of a propagating blast wave will activate resonant oscillations of the heavy mass within the inclusions. The resonant behavior causes the system to exhibit negative effective mass, and this interaction between the wave motion and the resonant aggregates results in the attenuation of the applied dynamic loading. We introduce the concept of negative mass by deriving the effective momentum mass for the system and we define the geometrical and material parameters for the design of resonant aggregates. We develop finite element models for the analysis of metaconcrete behavior, defining a section of slab containing a periodic arrangement of inclusions. By computing the energy histories for the system when subject to a blast load, we show that there is a transfer of energy between the inclusions and the surrounding mortar. The inclusions are able to absorb a significant portion of the applied energy, resulting in a reduction in the amount of stress carried by the mortar phase and greatly improving the ability of the material to resist damage under explosive dynamic loading.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Las esperanzas de que la Revolución Mexicana pusiera fin a la dictadura y trajera justicia para trabajadores y campesinos murieron pronto. Muchos investigadores han sugerido que las elecciones ...presidenciales de 1940 fueron el punto de no retorno. Pocos han conectado, sin embargo, las dos muertes que se produjeron ese año: el radicalismo -en la candidatura fallida de Francisco J. Múgica- y el sufragismo -en la desaparición silenciosa de una reforma constitucional-. Este artículo examina el breve período a principios de 1939 cuando dos cosas aún parecían posibles: Múgica podría ser el próximo presidente de México y las mujeres votarían en las elecciones. Con base en estos dos supuestos, Carolina Escudero Luján, secretaria y futura esposa de Múgica, organizó una campaña electoral nacional dirigida a las mujeres promotoras de la candidatura de Múgica. Mirar los dos fracasos uno al lado del otro nos permite ver cómo el mugiquismo y el sufragio femenino eran dos caras de la misma moneda. Vemos cómo y cuándo murió el potencial radical de la Revolución Mexicana.
•ID NOW EUA SARS-CoV-2 assay had an overall agreement of 78.7 % when compared to the standard of care reference methods.•ID NOW had a sensitivity of 71.7 % and specificity of 100 %.•All the ...false-negative results occurred with weakly positive samples, with reference method CT values ≥35.
The SARS-CoV-2 pandemic caused a major surge in needed diagnostic capacity. In response, many EUA assays have become available for clinical laboratories, and more recently, the point of care device, Abbott ID NOW.
To determine the analytical performance of the ID NOW assay for detecting SARS-CoV-2.
Residual NP samples collected in viral transport media were tested by the ID NOW platform in two independent laboratories. Results were compared to either the CDC or New York EUA assays, which served as reference methods.
Overall agreement of ID NOW was 78.7%. Sensitivity was 71.7% and specificity was 100%. Notably, all false-negative results correlated to those samples that were weakly positive.
ID NOW performs well for strong and moderately positive samples but has reduced sensitivity for weakly positive samples. This sensitivity, among other concerns, should be taken into consideration when using this test for patients with a low suspicion for COVID-19 disease.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Effective evaluations of antimicrobial susceptibility tests (ASTs) require robust study design. The Clinical and Laboratory Standards Institute (CLSI) Subcommittee on Antimicrobial Susceptibility ...Testing has recognized that many published studies reporting the performance of commercial ASTs (cASTs) suffer from major design and/or analysis flaws, rendering the results difficult or impossible to interpret. This minireview outlines the current consensus of the Methods Development and Standardization Working Group of the CLSI Subcommittee on Antimicrobial Susceptibility Testing regarding best practices for systematic evaluation of the performance of an AST, including the analysis and presentation of essential data intended for publication.
•Vaccine hesitancy is not homogenous requiring attention from all health communities.•Pregnant women may move between a continuum of vaccine hesitancy.•A framework is available to approach pregnant ...patient’s vaccine hesitations.
Pregnant women are often at higher risk for morbidity and mortality due to contracting vaccine-preventable diseases that result in adverse pregnancy outcomes such as spontaneous abortion, preterm births, and congenital fetal defects. For example, health care provider recommendation is correlated with maternal acceptance of influenza vaccination, however, up to 33 % of pregnant women remain unvaccinated irrespective of provider recommendation. Vaccine hesitancy is a multifactorial problem that both the medical and public health systems need to address synergistically. Vaccine education should incorporate balanced perspectives to deliver vaccine education. This narrative review addresses four questions: 1) what are the primary concerns of pregnant women that lead them to be hesitant about receiving vaccinations; 2) to what extent does the source (e.g. provider, friend, family) of vaccine advice and information influence a pregnant person’s decision to accept a vaccine; 3) how does the delivery method of vaccine education influence their decision; 4) how can categorizing patients into four distinct groups based on their opinions and behavior regarding vaccines be used to improve provider-patient communication and increase vaccine acceptance. Results from the literature show that the three most common reasons for vaccine hesitancy include: i.) fear of side effects or adverse events; ii.) lack of confidence in vaccine safety; iii.) low perception of being at high risk of infection during pregnancy and/or not having previously received the vaccination when not pregnant. We conclude that vaccine hesitancy is dynamic therefore people do not always hold a static level of vaccine hesitancy. People may move between a continuum of vaccine hesitancy for a multifactorial reasons. A framework, characterized by levels of vaccine hesitancy before and during pregnancy, was constructed to help providers find balance between promoting individual health and public health while providing vaccine education.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
COVID-19 disease lies on a spectrum, ranging from completely asymptomatic to mild disease to severe and critical disease. Studies have shown that prolonged shedding or sporadic detection of ...SARS-CoV-2 RNA can occur long after symptom resolution. Adding to these clinical complexities is the demand for testing for SARS-CoV-2 at all stages of diseases, frequently driven by screening of asymptomatic persons, something that traditionally has not been performed for other viral respiratory diseases. This can lead to positive results from nucleic acid amplification tests (NAATs), such as RT-PCR, with late cycle threshold (CT) values near the test's limit of detection. In this commentary, we review unique attributes of COVID-19 and causes of NAAT late CT values. We provide interpretation considerations as well as strategies to aid in test interpretation.
AbstractA new type of concrete, named metaconcrete, has been developed for the attenuation of shock waves induced by dynamic excitation. Inspired by the metamaterials used for the manipulation of ...electromagnetic and acoustic waves, this new metamaterial for the mitigation of shock waves utilizes the activation of resonance within engineered inclusions. Metaconcrete replaces the standard stone and gravel aggregates of regular concrete with spherical inclusions consisting of a heavy core coated in a compliant outer layer. Finite-element analyses of metaconcrete slabs for the case of purely elastic constituents reveal trapping of the supplied energy within the inclusions and a reduction in mortar stress, indicating the presence of resonance behavior within the aggregates. Mortar is, however, a brittle material and the fracture properties under dynamic loading should also be considered. Thus, the models used in the elastic analyses are extended by incorporating brittle fracture through the use of an eigenerosion scheme, which erodes elements satisfying an energy-based fracture criterion. The effect of different fracture parameters on the performance of the slab is investigated through parametric studies, looking at the change in slab behavior caused by various aggregate geometry and material configurations. These studies indicate that mechanical energy is captured by the aggregates, reducing the transmission of energy through the slab, the extension of the zone damaged by fracture, and the longitudinal stress within the mortar matrix. The understanding gained from these analyses incorporating fracture characteristics will enable more informed design of metaconcrete aggregates for dynamic loading applications, such as blast shielding and impact protection.
•Investigation of the transmission behavior of a new type of concrete metamaterial.•Metaconcrete consists of spherical engineered resonant aggregates suspended in mortar.•A transmission ratio is ...computed based on the absorption of wave energy.•Large dips in transmission ratio are observed at or near resonant frequencies.
A new type of modified concrete, termed metaconcrete, has been shown to exhibit trapping of wave energy and a reduction in mortar stress when subjected to dynamic loading. Metaconcrete replaces the standard stone and gravel aggregates of regular concrete with spherical inclusions consisting of a heavy core coated with a compliant outer layer. These new layered aggregates resonate at designed frequencies by allowing for relative motion between the heavy core and the mortar matrix, which causes the aggregate to absorb energy and therefore reduce stress within the mortar phase of the composite material. The transmission of wave energy through a metaconcrete slab can be used to visualize the effect of resonant behavior within the metaconcrete aggregates. To quantify this behavior we compute a transmission coefficient, which is a method of measuring the absorption of wave energy as an applied forcing of known frequency travels through the material. The transmission coefficient is plotted against forcing frequency for four different aggregate material and geometry configurations. A reduction in transmission ratio is observed at or near the computed natural modes of the aggregate, indicating the activation of resonance within the inclusions. This behavior is consistent with observations from studies on sonic metamaterials containing resonant inclusions with a similar layered structure. The frequency location and width of the dip in transmission coefficient will aid in the design of metaconcrete aggregates for specific forcing applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Penicillin-binding proteins (PBPs) play critical roles in cell wall construction, cell shape maintenance, and bacterial replication. Bacteria maintain a diversity of PBPs, indicating that despite ...their apparent functional redundancy, there is differentiation across the PBP family. Apparently-redundant proteins can be important for enabling an organism to cope with environmental stressors. In this study, we evaluated the consequence of environmental pH on PBP enzymatic activity in
. Our data show that a subset of PBPs in
change activity levels during alkaline shock and that one PBP isoform is rapidly modified to generate a smaller protein (i.e., PBP1a to PBP1b). Our results indicate that a subset of the PBPs are favored for growth under alkaline conditions, while others are readily dispensable. Indeed, we found that this phenomenon could also be observed in
, implying that it may be generalizable across additional bacterial species and further emphasizing the evolutionary benefit of maintaining many, seemingly-redundant periplasmic enzymes.IMPORTANCEMicrobes adapt to ever-changing environments and thrive over a vast range of conditions. While bacterial genomes are relatively small, significant portions encode for "redundant" functions. Apparent redundancy is especially pervasive in bacterial proteins that reside outside of the inner membrane. While conditions within the cytoplasm are carefully controlled, those of the periplasmic space are largely determined by the cell's exterior environment. As a result, proteins within this environmentally exposed region must be capable of functioning under a vast array of conditions, and/or there must be several similar proteins that have evolved to function under a variety of conditions. This study examines the activity of a class of enzymes that is essential in cell wall construction to determine if individual proteins might be adapted for activity under particular growth conditions. Our results indicate that a subset of these proteins are preferred for growth under alkaline conditions, while others are readily dispensable.
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