Light storage in wavy dielectric grating with Kerr nonlinearity

Periodical corrugation in dielectric slab transfers the two waveguide modes at zero Bloch wave number into a leaky resonant mode and a symmetry protected bound states in the continuum (BIC) with small frequency detune. The leaky resonant mode can be directly excited by weak linearly polarized normally incident optical field. In the presence of Kerr nonlinearity, the BIC can be indirectly excited by an optical bistable response. Two types of bistable operations are considered. For the first type, the intensity of the incident field gradually increases to exceed a critical value, and then decreases to zero. For the second type, the intensity is fixed, while the linear polarization angle of the incident field gradually increases to exceed a critical value, and then decreases to 0$^{o}$. Theoretically, the indirectly excited BIC can store the optical energy without loss, even though the intensity of the incident field decreases to zero. Incidence of an optical field with double frequency or orthogonal linear polarization can erase the stored optical field by destroying the BIC. The proposed optical system could function as optical storage and switching device

Mechanosensing model of fibroblast cells adhered on a substrate with varying stiffness and thickness

Mechanosensing of cells to the surrounding material is crucial for their physiological and pathological processes. However, materials design to guide cellular responses is largely ad hoc due to the lack of comprehensive modelling techniques for quantitative understanding. In this paper, we propose a computational model to study the mechanosensing of fibroblast cells seeded on elastic hydrogel substrates with different stiffness and thickness. We consider the sensing mechanisms of cells to mechanical cues, including the rigidity and deformation of the substrate, and the traction forces of neighboring cells, which regulate the active changes of stress fibers and focal adhesions. This model allows us to predict the coupled effects of substrate stiffness and thickness on stress fiber formation and disassociation, and affinity integrin density. We also examine the combined effect of cell size and substrate thickness on the mechanosensing of fibroblast cells. The results reveal that a cell can sense its neighboring cell by deforming the underlying substrate. Our simulations also provide physical insights in the enhanced mechanosensing capacity of collective cells. The present modelling framework is not only important for profound understanding of cell mechanosensing, but also has the potential to guide the rationale design of biomaterials for tissue engineering and wound healing.</p

Simultaneous measurement of single-cell mechanics and cell-to-materials adhesion using fluidic force microscopy

The connection between cells and their substrate is essential for biological processes such as cell migration. Atomic force microscopy nanoindentation has often been adopted to measure single-cell mechanics. Very recently, fluidic force microscopy has been developed to enable rapid measurements of cell adhesion. However, simultaneous characterization of the cell-to-material adhesion and viscoelastic properties of the same cell is challenging. In this study, we present a new approach to simultaneously determine these properties for single cells, using fluidic force microscopy. For MCF-7 cells grown on tissue-culture-treated polystyrene surfaces, we found that the adhesive force and adhesion energy were correlated for each cell. Well-spread cells tended to have stronger adhesion, which may be due to the greater area of the contact between cellular adhesion receptors and the surface. By contrast, the viscoelastic properties of MCF-7 cells cultured on the same surface appeared to have little dependence on cell shape. This methodology provides an integrated approach to better understand the biophysics of multiple cell types.</p

Major HLA class II alleles/allele groups in mothers and their children.

<p>Major HLA class II alleles/allele groups in mothers and their children.</p

PCR and sequencing primers used for genotyping HLA class II genes.

<p>PCR and sequencing primers used for genotyping HLA class II genes.</p

The major HLA-B-C haplotypes in Pumwani sex worker cohort.

<p>Note: The ‘n’ represents the number of subjects studied; ‘2n’ indicates number of chromosomes; Numbers in parentheses represent percent frequency.</p

Kaplan-Meier plot of HLA class I haplotypes associated with rapid HIV-1 disease progression, along with constituent alleles.

<p>(A) A*30∶02-B*45∶01; (B) A*30∶02; (C) B*45∶01; (D) A*30∶02-C*16∶01; (E) A*30∶02; (F) C*16∶01; (G) B*53∶01-C*04∶01; (H) B*53∶01; (I) C*04∶01; (J) B*15∶10-C*03∶04; (K) B*15∶10; (L) C*03∶04; (M) B*58∶01-C*03∶02; (N) B*58∶01; (O) C*03∶02. Solid line represents women with the specific haplotype or allele. Dashed line represents women without the specific haplotype or allele.</p

Kaplan-Meier plot of HLA class I haplotypes associated with rapid HIV-1 seroconversion, along with constituent alleles.

<p>(A) A*23∶01-C*02∶02; (B) A*23∶01; (C) C*02∶02; (D) B*42∶01-C*17∶01; (E) B*42∶01; (F) C*17∶01; (G) B*07∶02-C*07∶02; (H) B*07∶02; (I) C*07∶02. Solid line represents women with the specific haplotype or allele. Dashed line represents women without the specific haplotype or allele.</p

Backward Cox Regression analysis of haplotype effect on seroconversion.

<p>Backward Cox Regression analysis of haplotype effect on seroconversion.</p

HLA class I haplotypes associated with seroconversion and disease progression in Pumwani sex worker cohort.

<p>HLA class I haplotypes associated with seroconversion and disease progression in Pumwani sex worker cohort.</p