On Two Models of the Light Pulse Delay in a Saturable Absorber

A comparative analysis of two approaches to description of the light modulation pulse delay in a saturable absorber is presented. According to the simplest model, the delay of the optical pulse is a result of distortion of its shape due to absorption self-modulation in the nonlinear medium. The second model of the effect, proposed at the beginning of our century, connects the pulse delay with the so-called "slow light" resulting from the group velocity reduction under conditions of the coherent population oscillations. It is shown that all the known experimental data on the light pulse delay in saturable absorbers can be comprehensively described in the framework of the simplest model of saturable absorber and do not require invoking the effect of coherent population oscillations with spectral hole-burning and anomalous modifications of the light group velocity. It is concluded that the effect of group velocity reduction under conditions of coherent population oscillations has not received so far any experimental confirmation, and the assertions about real observation of the "slow light" based on this mechanism are groundless.Comment: Regretfully, the journal version of the paper (in Optics and Spectroscopy) appeared to be strongly corrupted due to ignorant editing. In particular, "coherent population oscillations" (CPO) was replaced by "population coherent oscillations" (PCO), "bleaching" - by "clearing", and "bleachable absorber " - by "clearable absorber". Here we present original version of the pape

Considerations for Post-processing Parameters in Mixed-Method 3D Analyses: A Mesolithic Mandibular Case Study

The production of three-dimensional (3D) digital meshes of surface and computed tomographic (CT) data has become widespread in morphometric analyses of anthropological and archaeological data. Given that processing methods are not standardized, this leaves questions regarding the comparability of processed and digitally curated 3D datasets. The goal of this study was to identify those processing parameters that result in the most consistent fit between CT-derived meshes and a 3D surface model of the same human mandible. Eight meshes, each using unique thresholding and smoothing parameters, were compared to assess whole-object deviations, deviations along curves, and deviations between specific anatomical features on the surface model when compared with the CT scans using a suite of comparison points. Based on calculated gap distances, the mesh that thresholded at “0” with an applied smoothing technique was found to deviate least from the surface model, although it is not the most biologically accurate. Results have implications for aggregated studies that employ multimodal 3D datasets, and caution is recommended for studies that enlist 3D data from websites and digital repositories, particularly if processing parameters are unknown or derived for studies with different research foci. La producción de mallas digitales tridimensionales (3D) de superficie e información tomográfica computarizada (TC) se ha generalizado en los analisis morfométricos de datos antropológicos y arqueológicos. Dado que los métodos de procesamiento no están estandarizados quedan dudas sobre la comparabilidad de conjuntos de datos 3D procesados y curados digitalmente. El objetivo de este estudio fue identificar los parámetros de procesamiento que tienen la compatibilidad más consistente entre mallas derivadas de TC y un modelo de superficie 3D de la misma mandibula humana. Fueron comparadas ocho mallas cada una con parámetros únicos de umbralización y suavizado, para evaluar las desviaciones de todo el objeto, las desviaciones a lo largo de las curvas y las desviaciones entre características anatómicas específicas en el modelo de superficie, en comparación con cada una de las tomografías computarizadas utilizando un conjunto de puntos de comparación. Con base en las distancias de separación calculadas, aunque no las más precisas desde el punto de vista biológico, se encontró que la malla con umbral en “0” con una técnica de suavizado aplicada se desvía menos de la superficie modelo. Los resultados tienen implicaciones para los estudios agregados que emplean conjuntos de datos 3D multimodales y se recomienda precaución para los estudios que incluyen datos 3D de sitios web y repositorios digitales, especialmente si los parámetros de procesamiento son desconocidos o derivados de estudios con diferentes focos de investigación

Representative bureaucracy: does female police leadership affect gender-based violence arrests?

Representative bureaucracy theory postulates that passive representation leads to active representation of minority groups. This article investigates the passive representation of female police officers at leadership levels and the active representation of women vis-a-vis gender-based violence arrest rates in the UK. Much of the extant research on representative bureaucracy is located at street level, with evidence showing that discretionary power of minority bureaucrats can lead to active representation. This article is focused on leadership levels of a public bureaucracy. The empirical research is based upon a panel dataset of female police officers as an independent variable and gender-based violence arrest rates as a dependent variable. The analysis reveals that there is little evidence of active representation of women by female police leadership

Lightweight sidewalls for aircraft interior noise control

A theoretical and experimental study was performed to devise lightweight sidewalls for turboprop aircraft. Seven concepts for new sidewalls were analyzed and tested for noise reduction using flat panels of 1.2 m x 1.8 m (4 ft x 6 ft), some of which were aircraft-type constructions and some of which were simpler, easier-to-construct panels to test the functioning of an acoustic principle. Aircraft-application sidewalls were then conceived for each of the seven concepts, and were subjectively evaluated for their ability to meet aircraft nonacoustic design requirements. As a result of the above, the following sidewall concepts were recommended for further investigation: a sidewall in which the interior cavity is vented to ceiling and underfloor areas; sidewalls with wall-mounted resonators, one having a conventional trim panel and one a limp one; and a sidewall with a stiff outer wall and a limp trim panel. These sidewalls appear to promise lower weights than conventional sidewalls adjusted to meet similar acoustic requirements, and further development may prove them to be practical

Experimental and Computational Study of Area and Perimeter Contributions to Radiometer Forces

The relative contribution to the radiometric force of the area and perimeter of the vane is studied experimentally and numerically. Experimentally, a circular vane, a low-aspect rectangular vane, and a high-aspect rectangular vane were all tested on a force balance, with nano-Newton resolution, placed in a stagnant gas. The computational results were obtained through 2-D simulations using the direct simulation Monte Carlo method, as well as a discrete ordinate solution of the ES model kinetic equation. Gas pressure was varied from 0.006 to 6 Pa, which was a broad enough range to observe the characteristic peak force production of a radiometer in the transition regime, where the peak occurs at Kn ~ 0.1. It was found that the area of a radiometer vane is responsible for a significant amount ofthe total force production through a wide range of operating pressures. It is only at the highest background pressures, well after force production has peaked, that the vane perimeter appears to dominate the operation of the radiometer

A golden orb-weaver spider (Araneae: Nephilidae: Nephila) from the Middle Jurassic of China

Nephila are large, conspicuous weavers of orb webs composed of golden silk, in tropical and subtropical regions. Nephilids have a sparse fossil record, the oldest described hitherto being Cretaraneus vilaltae from the Cretaceous of Spain. Five species from Neogene Dominican amber and one from the Eocene of Florissant, CO, USA, have been referred to the extant genus Nephila. Here, we report the largest known fossil spider, Nephila jurassica sp. nov., from Middle Jurassic (approx. 165 Ma) strata of Daohugou, Inner Mongolia, China. The new species extends the fossil record of the family by approximately 35 Ma and of the genus Nephila by approximately 130 Ma, making it the longest ranging spider genus known. Nephilidae originated somewhere on Pangaea, possibly the North China block, followed by dispersal almost worldwide before the break-up of the supercontinent later in the Mesozoic. The find suggests that the palaeoclimate was warm and humid at this time. This giant fossil orb-weaver provides evidence of predation on medium to large insects, well known from the Daohugou beds, and would have played an important role in the evolution of these insects

Impact of Storage at -80°C on Encapsulated Liver Spheroids After Liquid Nitrogen Storage

For many bioengineered tissues to have practical clinical application, cryopreservation for use on demand is essential. This study examined different thermal histories on warming and short holding periods at different subzero temperatures on subsequent functional recoveries of alginate encapsulated liver spheroids (ELS) for use in a bioartificial liver device. This mimicked transport at liquid nitrogen (-196°C) or dry ice (∼-80°C) temperatures. Holding at -80°C on warming after -196°C storage resulted in ELS expressing significant (p < 0.001) damage compared with direct thaw from liquid nitrogen, with viable cell number falling from 74.0 ± 8.4 million viable cells/mL without -80°C storage to 1.9 ± 0.6 million viable cells/mL 72 h post-thaw after 8 days storage at -80°C. Even 1 day at -80°C after -196°C storage resulted in lower viability (down 21% 24 h post-thaw), viable cell count (down 29% 24 h post-thaw), glucose, and alpha-1-fetoprotein production (reduced by 59% and 95% 24 h from 1 day post-thaw, respectively). Storage at -80°C was determined to be harmful only during the warming cycle. Chemical measurements of the alginate component of ELS were unchanged by cryogenic exposure in either condition

Extracellular fluid viscosity enhances liver cancer cell mechanosensing and migration

The extracellular fluid (ECF) is a crowded environment containing macromolecules that determine its characteristic density, osmotic pressure, and viscosity, which greatly differ between tissues. Precursors and products of degradation of biomaterials enhance ECF crowding and often increase its viscosity. Also, increases in ECF viscosity are related to mucin-producing adenocarcinomas. However, the effect of ECF viscosity on cells remains largely unexplored. Here we show that viscosity-enhancing polymer solutions promote mesenchymal-like cell migration in liver cancer cell lines. Also, we demonstrate that viscosity enhances integrin-dependent cell spreading rate and causes actin cytoskeleton re-arrangements leading to larger cell area, nuclear flattening, and nuclear translocation of YAP and β-catenin, proteins involved in mechanotransduction. Finally, we describe a relationship between ECF viscosity and substrate stiffness in determining cell area, traction force generation and mechanotransduction, effects that are actin-dependent only on ≤ 40 kPa substrates. These findings reveal that enhancing ECF viscosity can induce major biological responses including cell migration and substrate mechanosensing

Defining the Realized Niche of the Two Major Clades of \u3ci\u3eTrichodesmium\u3c/i\u3e: A Study on the West Florida Shelf

The cyanobacterium Trichodesmium plays an essential role supporting ocean productivity by relieving nitrogen limitation via dinitrogen (N-2) fixation. The two common Trichodesmium clades, T. erythraeum and T. thiebautii, are both observed in waters along the West Florida Shelf (WFS). We hypothesized that these taxa occupy distinct realized niches, where T. thiebautii is the more oceanic clade. Samples for DNA and water chemistry analyses were collected on three separate WFS expeditions (2015, 2018, and 2019) spanning multiple seasons; abundances of the single copy housekeeping gene rnpB from both clades were enumerated via quantitative PCR. We conducted a suite of statistical analyses to assess Trichodesmium clade abundances in the context of the physicochemical data. We observed a consistent coastal vs. open ocean separation of the two clades: T. erythraeum was found in shallow waters where the concentrations of dissolved iron (dFe) and the groundwater tracer Ba were significantly higher, while T. thiebautii abundance was positively correlated with water column depth. The Loop Current intrusion in 2015 with entrained Missisippi River water brought higher dFe and elevated abundance of both clades offshore of the 50 m isobath, suggesting that both clades are subject to Fe limitation on the outer shelf. Whereas, previous work has observed that T. thiebautii is more abundant than T. erythraeum in open ocean surface waters, this is the first study to examine Trichodesmium niche differentiation in a coastal environment. Understanding the environmental niches of these two key taxa bears important implications for their contributions to global nitrogen and carbon cycling and their response to global climate change