Raman Enhancement on a Broadband Meta-Surface

Cataloged from PDF version of article.Plasmonic metamaterials allow confinement of light to deep subwavelength dimensions, while allowing for the tailoring of dispersion and electromagnetic mode density to enhance specific photonic properties. Optical resonances of plasmonic molecules have been extensively investigated; however, benefits of strong coupling of dimers have been overlooked. Here, we construct a plasmonic meta-surface through coupling of diatomic plasmonic molecules which contain a heavy and light meta-atom. Presence and coupling of two distinct types of localized modes in the plasmonic molecule allow formation and engineering of a rich band structure in a seemingly simple and common geometry, resulting in a broadband and quasi-omni-directional meta-surface. Surface-enhanced Raman scattering benefits from the simultaneous presence of plasmonic resonances at the excitation and scattering frequencies, and by proper design of the band structure to satisfy this condition, highly repeatable and spatially uniform Raman enhancement is demonstrated. On the basis of calculations of the field enhancement distribution within a unit cell, spatial uniformity of the enhancement at the nanoscale is discussed. Raman scattering constitutes an example of nonlinear optical processes, where the wavelength conversion during scattering may be viewed as a photonic transition between the bands of the meta-material

Proteomic and Biological Analysis of the Effects of Metformin Senomorphics on the Mesenchymal Stromal Cells

Senotherapeutics are new drugs that can modulate senescence phenomena within tissues and reduce the onset of age-related pathologies. Senotherapeutics are divided into senolytics and senomorphics. The senolytics selectively kill senescent cells, while the senomorphics delay or block the onset of senescence. Metformin has been used to treat diabetes for several decades. Recently, it has been proposed that metformin may have anti-aging properties as it prevents DNA damage and inflammation. We evaluated the senomorphic effect of 6 weeks of therapeutic metformin treatment on the biology of human adipose mesenchymal stromal cells (MSCs). The study was combined with a proteome analysis of changes occurring in MSCs’ intracellular and secretome protein composition in order to identify molecular pathways associated with the observed biological phenomena. The metformin reduced the replicative senescence and cell death phenomena associated with prolonged in vitro cultivation. The continuous metformin supplementation delayed and/or reduced the impairment of MSC functions as evidenced by the presence of three specific pathways in metformin-treated samples: 1) the alpha-adrenergic signaling, which contributes to regulation of MSCs physiological secretory activity, 2) the signaling pathway associated with MSCs detoxification activity, and 3) the aspartate degradation pathway for optimal energy production. The senomorphic function of metformin seemed related to its reactive oxygen species (ROS) scavenging activity. In metformin-treated samples, the CEBPA, TP53 and USF1 transcription factors appeared to be involved in the regulation of several factors (SOD1, SOD2, CAT, GLRX, GSTP1) blocking ROS

Plasmonic absorbers for multispectral and broadband absorption

We present polarization dependent multispectral and broadband plasmonic absorbers in the visible spectrum. The spectral characteristics of these structures are tunable over a broad spectrum. Experimental results are verified with the FDTD and RCWA analysis methods. These structures are used as surface enhanced raman spectroscopy(SERS) substrates. Designed structures have resonances that span the Raman Stokes and excitation wavelength. Such structures can be used for energy, LED and other spectroscopy applications. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)

Grating coupler integrated photodiodes for plasmon resonance based sensing in fluidic systems

We demonstrate an integrated sensor combining a grating-coupled plasmon resonance surface with a planar photodiode. Plasmon enhanced transmission is employed as a sensitive refractive index (RI) sensing mechanism and monitored via the integrated photodiode. © 2011 OSA

Impact of antimicrobial drug restrictions on doctors' behaviors

Background/aim: Broad-spectrum antibiotics have become available for use only with the approval of infectious disease specialists (IDSs) since 2003 in Turkey. This study aimed to analyze the tendencies of doctors who are not disease specialists (non-IDSs) towards the restriction of antibiotics.Materials and methods: A questionnaire form was prepared, which included a total of 22 questions about the impact of antibiotic restriction (AR) policy, the role of IDSs in the restriction, and the perception of this change in antibiotic consumption. The questionnaire was completed by each participating physician.Results: A total of 1906 specialists from 20 cities in Turkey participated in the study. Of those who participated, 1271 (67.5%) had 5 years of occupational experience in their branch expressed that they followed the antibiotic guidelines more strictly than the JSs (P < 0.05) and 755 of physicians (88%) and 720 of surgeons (84.6%) thought that the AR policy was necessary and useful (P < 0.05).Conclusion: This study indicated that the AR policy was supported by most of the specialists. Physicians supported this restriction policy more so than surgeons did

Bias associated with delayed verification in test accuracy studies: accuracy of tests for endometrial hyperplasia may be much higher than we think!

BACKGROUND: To empirically evaluate bias in estimation of accuracy associated with delay in verification of diagnosis among studies evaluating tests for predicting endometrial hyperplasia. METHODS: Systematic reviews of all published research on accuracy of miniature endometrial biopsy and endometr ial ultrasonography for diagnosing endometrial hyperplasia identified 27 test accuracy studies (2,982 subjects). Of these, 16 had immediate histological verification of diagnosis while 11 had verification delayed > 24 hrs after testing. The effect of delay in verification of diagnosis on estimates of accuracy was evaluated using meta-regression with diagnostic odds ratio (dOR) as the accuracy measure. This analysis was adjusted for study quality and type of test (miniature endometrial biopsy or endometrial ultrasound). RESULTS: Compared to studies with immediate verification of diagnosis (dOR 67.2, 95% CI 21.7–208.8), those with delayed verification (dOR 16.2, 95% CI 8.6–30.5) underestimated the diagnostic accuracy by 74% (95% CI 7%–99%; P value = 0.048). CONCLUSION: Among studies of miniature endometrial biopsy and endometrial ultrasound, diagnostic accuracy is considerably underestimated if there is a delay in histological verification of diagnosis

Combining Optimal Control Theory and Molecular Dynamics for Protein Folding

A new method to develop low-energy folding routes for proteins is presented. The novel aspect of the proposed approach is the synergistic use of optimal control theory with Molecular Dynamics (MD). In the first step of the method, optimal control theory is employed to compute the force field and the optimal folding trajectory for the atoms of a Coarse-Grained (CG) protein model. The solution of this CG optimization provides an harmonic approximation of the true potential energy surface around the native state. In the next step CG optimization guides the MD simulation by specifying the optimal target positions for the atoms. In turn, MD simulation provides an all-atom conformation whose positions match closely the reference target positions determined by CG optimization. This is accomplished by Targeted Molecular Dynamics (TMD) which uses a bias potential or harmonic restraint in addition to the usual MD potential. Folding is a dynamical process and as such residues make different contacts during the course of folding. Therefore CG optimization has to be reinitialized and repeated over time to accomodate these important changes. At each sampled folding time, the active contacts among the residues are recalculated based on the all-atom conformation obtained from MD. Using the new set of contacts, the CG potential is updated and the CG optimal trajectory for the atoms is recomputed. This is followed by MD. Implementation of this repetitive CG optimization - MD simulation cycle generates the folding trajectory. Simulations on a model protein Villin demonstrate the utility of the method. Since the method is founded on the general tools of optimal control theory and MD without any restrictions, it is widely applicable to other systems. It can be easily implemented with available MD software packages