Viscous effects in Rayleigh-Taylor instability

A simple, physical approximation is developed for the effect of viscosity for stable interfacial waves and for the unstable interfacial waves which correspond to Rayleigh‐Taylor instability. The approximate picture is rigorously justified for the interface between a heavy fluid (e.g., water) and a light fluid (e.g., air) with negligible dynamic effect. The approximate picture may also be rigorously justified for the case of two fluids for which the differences in density and viscosity are small. The treatment of the interfacial waves may easily be extended to the case where one of the fluids has a small thickness; that is, the case in which one of the fluids is bounded by a free surface or by a rigid wall. The theory is used to give an explanation of the bioconvective patterns which have been observed with cultures of microorganisms which have negative geotaxis. Since such organisms tend to collect at the surface of a culture and since they are heavier than water, the conditions for Rayleigh‐Taylor instability are met. It is shown that the observed patterns are quite accurately explained by the theory. Similar observations with a viscous liquid loaded with small glass spheres are described. A behavior similar to the bioconvective patterns with microorganisms is found and the results are also explained quantitatively by Rayleigh‐Taylor instability theory for a continuous medium with viscosity

Acetylated Triterpene Glycosides and Their Biological Activity from Holothuroidea Reported in the Past Six Decades

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).Sea cucumbers have been valued for many centuries as a tonic and functional food, dietary delicacies and important ingredients of traditional medicine in many Asian countries. An assortment of bioactive compounds has been described in sea cucumbers. The most important and abundant secondary metabolites from sea cucumbers are triterpene glycosides (saponins). Due to the wide range of their potential biological activities, these natural compounds have gained attention and this has led to their emergence as high value compounds with extended application in nutraceutical, cosmeceutical, medicinal and pharmaceutical products. They are characterized by bearing a wide spectrum of structures, such as sulfated, non-sulfated and acetylated glycosides. Over 700 triterpene glycosides have been reported from the Holothuroidea in which more than 145 are decorated with an acetoxy group having 38 different aglycones. The majority of sea cucumber triterpene glycosides are of the holostane type containing a C18 (20) lactone group and either D7(8) or D9(11) double bond in their genins. The acetoxy group is mainly connected to the C-16, C-22, C-23 and/or C-25 of their aglycone. Apparently, the presence of an acetoxy group, particularly at C-16 of the aglycone, plays a significant role in the bioactivity; including induction of caspase, apoptosis, cytotoxicity, anticancer, antifungal and antibacterial activities of these compounds. This manuscript highlights the structure of acetylated saponins, their biological activity, and their structure-activity relationships

Comments on "Rayleigh–Taylor instability of thin viscous layers"

In a paper by Craik, (1) frequent references are made to our paper (2) which we believe are incorrect. It may also be pointed out that quite unusual circumstances would be required to provide a physical basis for Craik’s analysis; the experiments described in his paper are not appropriately explained by his analysis

A phenomenological hermeneutic investigation into the psychoanalytic psychotherapist's experience of using the psychoanalytic couch

The aim of this study was to describe and critically explore the psychoanalytic, psychotherapist's lived experience of the technique of using the couch. Through examination of the literature a question was formulated that would disclose the analyst's experience of the technique of using the couch. Four experienced psychoanalytic practitioners who could be operationally defined as 'analysts' were interviewed. Using a phenomenological method the protocols were comprehensively analyzed to produce descriptions of the general structure of the experience. These were then texturally enhanced using interleaved direct citations from the interviews. The structural and textural 'findings ' so produced were then hermeneutically dialogued with contemporary psychoanalytic notions of critical discourse and intersubjectivity. The phenomenological ' findings ' of the study disclosed the meaning of the couch as context-based, paradoxical and ambiguous. The couch was found to be a symbol of the analyst as analyst and the process as authentic analysis. Furthermore, at its best, the couch was found to mediate a mode of being that is containing and intimate and in which psychological life may be evoked, tracked and interpreted. The most significant contributor to this mode of being was found to be privacy, which, in particular, helps the analyst maintain an analytic attitude. The couch was also found to be significantly implicated in the generation of an intersubjective analytic third and to support reverie. These 'findings' were hermeneutically dialogued with literature on the couch as well as contemporary psychoanalytic theoretical notions. The dialogue fell into three foci. The first focus entailed deconstructing the meaning of the couch as context-based and ambiguous and not essential. The second pursued critiques of the role that the couch plays in domination, of its function as a symbol/evocative object and of the way in which it shapes being-together, bodily attunement, privacy, the intersubjective analytic third and reverie. Finally the 'findings' were critically examined in terms of both Lacan's notion 'analytic discourse ' and its role in revealing/concealing the analysand as subject. The study concludes with an examination of its own limitations and suggestions for further research

The phase of pre-stimulus alpha oscillations influences the visual perception of stimulus timing

AbstractThis study examined the influence of pre-stimulus alpha phase and attention on whether two visual stimuli occurring closely in time were perceived as simultaneous or asynchronous. The results demonstrated that certain phases of alpha in the period immediately preceding stimulus onset were associated with a higher proportion of stimuli judged to be asynchronous. Furthermore, this effect was shown to occur independently of both visuo-spatial attention and alpha amplitude. The findings are compatible with proposals that alpha phase reflects cyclic shifts in neuronal excitability. Importantly, however, the results further suggest that fluctuations in neuronal excitability can create a periodicity in neuronal transfer that can have functional consequences that are decoupled from changes in alpha amplitude. This study therefore provides evidence that perceptual processes fluctuate periodically although it remains uncertain whether this implies the discrete temporal framing of perception

Leptomeningeal Metastases in High-Grade Adult Glioma: Development, Diagnosis, Management, and Outcomes in a Series of 34 Patients

Leptomeningeal metastases (LM) in the setting of glioma have often been thought to carry a particularly poor prognosis. We sought to better characterize this phenomenon through a review of patients with glioma seen in our institution over the preceding 10 years. We focus here on 34 cases with LM due to grade III or IV glioma. Over the period in question we estimate a prevalence of almost 4% in those affected by grade IV tumors. Leptomeningeal spread was present at the time of initial diagnosis in 4 patients. In the others, LM occurred at the time of first progression of disease in 17. The median time to development of LM (excluding those where it was present at initial diagnosis) was 16.4 months (95% confidence interval (CI) 8.2-43.9). The median time to further progression of disease following LM was 4.9 months (95% CI 3.1- 6.9). 25 patients were known to have died at the time of writing. Thus median overall survival (OS) was 10.2 months (95% CI 8.8-14.7) following LM. At the time of diagnosis of LM, some form of treatment (chemotherapy and/or radiation vs. no treatment) increased OS (median 11.7 vs. 3.3 months, p\u3c0.001 by log-rank test). Use of radiation therapy (vs. no radiation) also increased OS, although the effect was more modest (7.8 vs. 16.8 months, p=0.07). Higher Karnofsky Performance Status (KPS) at the time of diagnosis of LM was associated with OS (p=0.007, median OS for KPS ‰¥90 19 months vs. 7.8 for KPS \u3c90). In a two-variable model incorporating the use any treatment (vs. none) and KPS, KPS tended to be a more significant predictor of survival (p=0.22 vs. p=0.06 by likelihood-ratio test). This was also true for radiation (vs. none) and KPS (p=0.27 vs. p=0.02). No significant benefit could be demonstrated for the use of chemotherapy considered alone, either systemic or intrathecal. It should be noted that 4 of 9 patients receiving intrathecal chemotherapy had a ventriculoperitoneal shunt in place during these injections, which may have reduced its effectiveness

Brown Beauty: Body Image, Latinas, and the Media

This paper examines the understudied Latina population and the effects of media on their body image. To date, research has ignored this population or aggregated all Latin-American sub-cultures into one general category, missing the nuances of each culture. A review of current literature utilizing cultivation theory and social comparison theory is offered. Important findings suggest that social support and ethnic identity may offer a buffering effect between media exposure and body dissatisfaction, but more research needs to clarify this process. The effects of media and the internalization of the ‘thin ideal’ become stronger the longer Latina women live in the United States and acculturate to mainstream culture. Implications for body image research include psychological issues, such as lower self-esteem, depression, and anxiety, and can often lead to disordered eating. Future directions for studies are discussed

The usefulness of the story of the alchemical vessel in the understanding and psychotherapy of borderline conditions: a case study

The principal intention of this study was to explore the heuristic value of the story of the alchemical vessel in understanding borderline conditions and pursuing their psychotherapy. It establishes the pertinence of the case study as a method of exploring the content and process of psychotherapy. The essential nature of story-telling is examined and the hypothesis is made that psychotherapy, borderline conditions, the myth of the alchemical vessel and the case study all reflect instances of story-telling. Towards the end of examining their mutual reflection, and thus heuristic value, elements of Jungian theory, the phenomenology of borderline conditions and case material are examined. Through the examination of certain shared themes which emerge from the story of the alchemical vessel and the material of psychotherapy it is established that there is indeed a metaphoric resonance between the different stories. Furthermore this resonance is useful in that it provides a secure vantage point as well as guidance towards effecting transformation for the client. The validity of the metaphoric resonance is examined and areas of weakness highlighted. Some suggestions are made concerning further research

The usefulness of the story of the alchemical vessel in the understanding and psychotherapy of borderline conditions: a case study

The principal intention of this study was to explore the heuristic value of the story of the alchemical vessel in understanding borderline conditions and pursuing their psychotherapy. It establishes the pertinence of the case study as a method of exploring the content and process of psychotherapy. The essential nature of story-telling is examined and the hypothesis is made that psychotherapy, borderline conditions, the myth of the alchemical vessel and the case study all reflect instances of story-telling. Towards the end of examining their mutual reflection, and thus heuristic value, elements of Jungian theory, the phenomenology of borderline conditions and case material are examined. Through the examination of certain shared themes which emerge from the story of the alchemical vessel and the material of psychotherapy it is established that there is indeed a metaphoric resonance between the different stories. Furthermore this resonance is useful in that it provides a secure vantage point as well as guidance towards effecting transformation for the client. The validity of the metaphoric resonance is examined and areas of weakness highlighted. Some suggestions are made concerning further research

Selection of microbes for control of Rhizoctonia root rot on wheat using a high throughput pathosystem

© 2017 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http:// creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 12 month embargo from date of publication (July 2017) in accordance with the publisher’s archiving policyThe promise of microbial biological control of soilborne fungal pathogens of crops has yet to be fully realised with only a few strains commercialised and available to growers. One bottleneck is the availability of suitable methods to screen microorganisms for disease control efficacy relevant to controlling disease in the field. A 3-phase in planta pathosystem containing field soil was developed to screen 2310 microorganisms for control of Rhizoctonia root rot on wheat. Test strains were added to seeds as a suspension at planting and plant growth assessed at two weeks. Strains increasing plant height and number of roots (185) were tested in a replicated Rhizoctonia pot bioassay with five wheat seedlings grown for four weeks and assessed for plant growth and root disease. Forty-three strains (1.9% of strains tested) performed better than our benchmark strains and were reassessed in pot bioassays at three inoculation levels. These tested strains represented a wide diversity of microbial genotypes including fungi, (Trichoderma, Aspergillus and Cylindrocarpon) and bacteria encompassing four phyla (Actinobacteria, Firmicutes, Proteobacteria, Bacteroidetes). These results show that microbes can be successfully and rapidly screened directly for disease control on plants