Cholesteric liquid crystals (CLCs) are selectively reflective materials that can exhibit a number of dynamic optical responses. We recently reported on electrically-induced, seven-fold increase in ...bandwidth in polymer stabilized CLCs (PSCLCs) subjected to DC electric fields. Here, the underlying mechanism of the electrically-controllable bandwidth broadening in PSCLCs is isolated by employing a variety of electro-optic experiments. We conclude that the mechanism is ionic charge trapping by the polymer network which subjects the material system to pitch expansion near the positive electrode and pitch compression near the negative electrode resulting in approximately linear pitch variation throughout the cell thickness.
We investigate particle diffusion in a heterogeneous medium limited by a surface where sorption–desorption processes are governed by a kinetic equation. We consider that the dynamics of the particles ...present in the medium are governed by a diffusion equation with a spatial dependence on the diffusion coefficient, i.e., K(x) = D|x|−η, with −1 < η and D = const, respectively. This system is analyzed in a semi-infinity region, i.e., the system is defined in the interval 0,∞) for an arbitrary initial condition. The solutions are obtained and display anomalous spreading, that is, the dynamics may be viewed as anomalous diffusion, which in turn is related, and hence, the model can be directly applied to several complex systems ranging from biological fluids to electrolytic cells.
Molecular profiling studies have enabled discoveries for metastatic prostate cancer (MPC) but have predominantly occurred in academic medical institutions and involved non-representative patient ...populations. We established the Metastatic Prostate Cancer Project (MPCproject,
mpcproject.org
), a patient-partnered initiative to involve patients with MPC living anywhere in the US and Canada in molecular research. Here, we present results from our partnership with the first 706 MPCproject participants. While 41% of patient partners live in rural, physician-shortage, or medically underserved areas, the MPCproject has not yet achieved racial diversity, a disparity that demands new initiatives detailed herein. Among molecular data from 333 patient partners (572 samples), exome sequencing of 63 tumor and 19 cell-free DNA (cfDNA) samples recapitulated known findings in MPC, while inexpensive ultra-low-coverage sequencing of 318 cfDNA samples revealed clinically relevant
AR
amplifications. This study illustrates the power of a growing, longitudinal partnership with patients to generate a more representative understanding of MPC.
Crowdis et al. describe the MPCproject (
mpcproject.org
), a decentralized initiative to partner with patients with metastatic prostate cancer in the US and Canada to accelerate molecular research. The authors describe clinicogenomic results from the first 706 geographically diverse patient partners and lay the foundation for sustained and inclusive partnership in this disease.
This dissertation research is focused on understanding aspects of cholesteric liquid crystals when different effects are taken into account, such as external field, surface alignment effect and guest ...materials, aiming possible applications such as for displays. More specifically, we studied the effect of different chiral dopants on the physical properties of the nematic host, showing that large changes may happen depending on the nature of the dopant, which as a matter of practicality, can be used for designing better displays. We found a naturally occurring chiral dopant that improves many physical parameters of the nematic host, yielding better displays. We also studied the effect of external electric fields and the transitions between cholesteric textures. This study led us to propose driving schemes and display designs, where extensive efforts were made to optimize active and passive matrices for bistable cholesteric displays. We also performed studies on the surface effect for improving the features of cholesteric displays. Furthermore, we used a surface enhanced effect to study the wetting of cholesteric liquid crystals under the isotropic-cholesteric transition and the stripe pattern occurring in the wetting layer. By using experiments and computer simulations we have shows that the delicate anchoring at the isotropic-cholesteric interface induces the pattern observed, depending on the elastic anisotropy and pitch length of the material. We also present a study of reflection broadening induced by DC fields when a small amount of polymer is dispersed in the cholesteric material, which is a great advantage over previous reported methods to induce bandwidth broadening and can be used as a switchable mirror. We propose a mechanism to explain the data. Last we include results on cholesteric phases made with bent-cores, and mixtures of bent-core and rod-like cholesteric liquid crystals. The results found in this last chapter yields the possibility of UV detectors as well as cholesteric displays sensitive to light, temperature and electric field.
The recently discovered twist-bend nematic phase, \(\rm N_{tb}\), is a non-uniform equilibrium nematic phase that presents a spontaneous bend with a precession of the nematic director, ...\(\textbf{n}\), on a conical helix with a tilt angle \(\theta\) and helical pitch \(P\). The stability of the \(\rm N_{tb}\) phase has been recently demonstrated from the elastic point of view by extending the Frank elastic energy density of the nematic phase to include the symmetry element of helical axis, \(\bf t\). In the present communication, we investigate the influence of an external bulk field (magnetic or electric) on the pitch of the \(\rm N_{tb}\) phase. For a material with positive magnetic susceptibility anisotropy, when the magnetic field \(\bf{H}\) is parallel to the helical axis, \(\bf{t}\), the field modifies the coupling parameter between the director and the helical axis, thus shifting the interval of values for which this coupling results in the \(\rm N_{tb}\) phase. If \(\bf{H}\) is perpendicular to \(\bf{t}\), it is shown that the pitch of the nematic director \(\bf n\) precession increases with \(\bf{H}\), and at a critical value of \(H_c\) it becomes infinite as in a cholesteric liquid crystal, that is, one gets a uniform orientation of n. Our results include the behaviour of a cholesteric under field as a limiting case.
The twist-bend nematic phase, \(N_{\rm TB}\), may be viewed as a heliconical molecular arrangement in which the director \(\bf n\) precesses uniformly about an extra director field, \(\bf t\). It ...corresponds to a nematic ground state exhibiting nanoscale periodic modulation. To demonstrate the stability of this phase from the elastic point of view, a natural extension of the Frank elastic energy density is proposed. The elastic energy density is built in terms of the elements of symmetry of the new phase in which intervene the components of these director fields together with the usual Cartesian tensors. It is shown that the ground state corresponds to a deformed state for which \(K_{22} > K_{33}\). When the elastic free energy is interpreted in analogy with the Landau theory, it is demonstrated the existence of a second order phase transition between the usual and the twist-bend nematic phase, driven by a new elastic parameter playing a role similar to the one of the main dielectric anisotropy of classical nematics and being closely related to the bulk compression modulus representing the pseudo-layers of twist-bend nematic phases. A phase transition and the value of the nanoscale pitch are predicted in accordance to experimental results.
IntroductionCytomegalovirus (CMV) infection is common among patients with human immunodeficiency virus (HIV) infection. Gastrointestinal (GI) involvement with tumor like lesion is a rare ...presentation. Our patient presented with rectal pain and findings concerning for malignancy. Subsequently our patient was diagnosed with acquired immunodeficiency syndrome (AIDS), CMV viremia and CMV proctitis. CaseA 37-year-old man who reported having sex with men presented with severe proctalgia and hematochezia. Imaging showed irregular rectal wall thickening concerning for malignancy. Sigmoidoscopy revealed a circumferential necrotic lesion suspicious for malignancy. Surprisingly, biopsy showed a cytopathic effect compatible with CMV infection. In addition to testing positive for CMV, patient was newly diagnosed with HIV/AIDS, hepatitis C, syphilis, and gonorrhea. CMV infection was treated with ganciclovir, which resulted in a significant response. Ganciclovir was later replaced with valganciclovir. Valganciclovir was continued and antiretroviral therapy (ART) was started as an outpatient and with resolution of symptoms. DiscussionCMV infection is one of the most common opportunistic infections among patients with HIV infection. Several cases of CMV colitis were reported among immunocompromised patients. Our patient's presenting symptoms and direct visualization of rectal lesion were not only deceptive but also unique. As what looked like a rectal malignancy was later diagnosed as tissue invasive CMV by biopsy. Invasive CMV infection should be managed with ganciclovir. ConclusionGI CMV as the initial presentation of HIV is rare. Moreover, CMV proctitis can masquerade as a rectal cancer and clinicians should be aware of this rare presentation of CMV.
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