41 research outputs found
Nanoscale Dynamics of Phase Flipping in Water near its Hypothesized Liquid-Liquid Critical Point
Achieving a coherent understanding of the many thermodynamic and dynamic
anomalies of water is among the most important unsolved puzzles in physics,
chemistry, and biology. One hypothesized explanation imagines the existence of
a line of first order phase transitions separating two liquid phases and
terminating at a novel "liquid-liquid" critical point in a region of low
temperature () and high pressure (). Here we analyze a common model of water, the ST2 model, and find
that the entire system flips between liquid states of high and low density.
Further, we find that in the critical region crystallites melt on a time scale
of nanoseconds. We perform a finite-size scaling analysis that accurately
locates both the liquid-liquid coexistence line and its associated
liquid-liquid critical point.Comment: 22 pages, 5 figure
Validation of diffusion tensor MRI measurements of cardiac microstructure with structure tensor synchrotron radiation imaging.
Background
Diffusion tensor imaging (DTI) is widely used to assess tissue microstructure non-invasively. Cardiac DTI enables inference of cell and sheetlet orientations, which are altered under pathological conditions. However, DTI is affected by many factors, therefore robust validation is critical. Existing histological validation is intrinsically flawed, since it requires further tissue processing leading to sample distortion, is routinely limited in field-of-view and requires reconstruction of three-dimensional volumes from two-dimensional images. In contrast, synchrotron radiation imaging (SRI) data enables imaging of the heart in 3D without further preparation following DTI. The objective of the study was to validate DTI measurements based on structure tensor analysis of SRI data.
Methods
One isolated, fixed rat heart was imaged ex vivo with DTI and X-ray phase contrast SRI, and reconstructed at 100 ÎŒm and 3.6 ÎŒm isotropic resolution respectively. Structure tensors were determined from the SRI data and registered to the DTI data.
Results
Excellent agreement in helix angles (HA) and transverse angles (TA) was observed between the DTI and structure tensor synchrotron radiation imaging (STSRI) data, where HADTI-STSRIâ=ââ1.4°â±â23.2° and TADTI-STSRIâ=ââ1.4°â±â35.0° (meanâ±â1.96 standard deviation across all voxels in the left ventricle). STSRI confirmed that the primary eigenvector of the diffusion tensor corresponds with the cardiomyocyte long-axis across the whole myocardium.
Conclusions
We have used STSRI as a novel and high-resolution gold standard for the validation of DTI, allowing like-with-like comparison of three-dimensional tissue structures in the same intact heart free of distortion. This represents a critical step forward in independently verifying the structural basis and informing the interpretation of cardiac DTI data, thereby supporting the further development and adoption of DTI in structure-based electro-mechanical modelling and routine clinical applications
Transcription factor NF-ÎșB is modulated by symbiotic status in a sea anemone model of cnidarian bleaching
Abstract Transcription factor NF-ÎșB plays a central role in immunity from fruit flies to humans, and NF-ÎșB activity is altered in many human diseases. To investigate a role for NF-ÎșB in immunity and disease on a broader evolutionary scale we have characterized NF-ÎșB in a sea anemone (Exaiptasia pallida; called Aiptasia herein) model for cnidarian symbiosis and dysbiosis (i.e., âbleachingâ). We show that the DNA-binding site specificity of Aiptasia NF-ÎșB is similar to NF-ÎșB proteins from a broad expanse of organisms. Analyses of NF-ÎșB and IÎșB kinase proteins from Aiptasia suggest that non-canonical NF-ÎșB processing is an evolutionarily ancient pathway, which can be reconstituted in human cells. In Aiptasia, NF-ÎșB protein levels, DNA-binding activity, and tissue expression increase when loss of the algal symbiont Symbiodinium is induced by heat or chemical treatment. Kinetic analysis of NF-ÎșB levels following loss of symbiosis show that NF-ÎșB levels increase only after Symbiodinium is cleared. Moreover, introduction of Symbiodinium into naĂŻve Aiptasia larvae results in a decrease in NF-ÎșB expression. Our results suggest that Symbiodinium suppresses NF-ÎșB in order to enable establishment of symbiosis in Aiptasia. These results are the first to demonstrate a link between changes in the conserved immune regulatory protein NF-ÎșB and cnidarian symbiotic status
A qualitative inquiry on pregnant womenâs preferences for mental health screening
Abstract Background Approaches to screening can influence the acceptance of and comfort with mental health screening. Qualitative evidence on pregnant womenâs comfort with different screening approaches and disclosure of mental health concerns is scant. The purpose of this study was to understand womenâs perspectives of different mental health screening approaches and the perceived barriers to the communication and disclosure of their mental health concerns during pregnancy. Methods A qualitative descriptive study was undertaken. Fifteen women, with a singleton pregnancy, were recruited from a community maternity clinic and a mental health clinic in Calgary, Canada. Semi-structured interviews were conducted during both the 2nd and 3rd trimesters. Data were analyzed using thematic analysis. Results Preferences for mental health screening approaches varied. Most women with a known mental health issue preferred a communicative approach, while women without a known mental health history who struggled with emotional problems were inclined towards less interactive approaches and reported a reluctance to share their concerns. Barriers to communicating mental health concerns included a lack of emotional literacy (i.e., not recognizing the symptoms, not understanding the emotions), fear of disclosure outcomes (i.e., fear of being judged, fear of the consequences), feeling uncomfortable to be seen vulnerable, perception about the role of prenatal care provider (internal barriers); the lack of continuity of care, depersonalized care, lack of feedback, and unfamiliarity with/uncertainty about the availability of support (structural barriers). Conclusions The overlaps between some themes identified for the reasons behind a preferred screening approach and barriers reported by women to communicate mental health concerns suggest that having options may help women overcome some of the current disclosure barriers and enable them to engage in the process. Furthermore, the continuity of care, clarity around the outcomes of disclosing mental health concerns, and availability of immediate support can help women move from providing âthe best answerâ to providing an authentic answer