Elastic Wave Fields Generated by Shear Horizontal Piezoelectric Fiber Patch (SH-PFP) Transducers: Parameter Study by Modelling and Laser Vibrometric Measurements

Recently, a novel lightweight and thin piezoelectric transducer was proposed [1-3]. It generates in-plane surface tractions and thus shear horizontal elastic waves in both bulk materials and waveguides. The paper describes the principle of operation of this Shear Horizontal Piezoelectric Fiber Patch (SH-PFP). In continuation of the previous work, several variants of the SH-PFP are studied. The generated wavefield is characterized bywavefield snapshots and directivity functions. Both numerical simulation and measurements by 3D Laser Vibrometry are performed and the results are compared, showing a good agreement. We discuss possible further developments of the SH-PFP transducer to allow 1D directivity and we also discuss various possible sensor applications

Photonic mode density effects on single-molecule fluorescence blinking

We investigated the influence of the photonic mode density (PMD) on the triplet dynamics of individual chromophores on a dielectric interface by comparing their response in the presence and absence of a nearby gold film. Lifetimes of the excited singlet state were evaluated in ordet to measure directly the PMD at the molecules position. Triplet state lifetimes were simultaneously determined by statistical analysis of the detection time of the fluorescence photons. The observed singlet decay rates are in agreement with the predicted PMD for molecules with different orientations. The triplet decay rate is modified in a fashion correlated to the singlet decay rate. These results show that PMD engineering can lead to an important suppression of the fluorescence, introducing a novel aspect of the physical mechanism to enhance fluorescence intensity in PMD-enhancing systems such as plasmonic devices

Endothelial SIRT6 deficiency promotes arterial thrombosis in mice

OBJECTIVE Arterial thrombosis may be initiated by endothelial inflammation or denudation, activation of blood-borne elements or the coagulation system. Tissue factor (TF), a central trigger of the coagulation cascade, is regulated by the pro-inflammatory NF-κB-dependent pathways. Sirtuin 6 (SIRT6) is a nuclear member of the sirtuin family of NAD$^{+}$-dependent deacetylases and is known to inhibit NF-κB signaling. Its constitutive deletion in mice shows early lethality with hypoglycemia and accelerated aging. Of note, the role of SIRT6 in arterial thrombosis remains unknown. Thus, we hypothesized that endothelial SIRT6 protects from arterial thrombosis by modulating inhibition of NF-κB-associated pathways. APPROACH AND RESULTS Using a laser-induced carotid thrombosis model, in vivo arterial occlusion occurred 45% faster in 12-week-old male endothelial-specific Sirt6$^{-/-}$ mice as compared to Sirt6$^{fl/fl}$ controls (n ≥ 9 per group; p = 0.0012). Levels of procoagulant TF were increased in animals lacking endothelial SIRT6 as compared to control littermates. Similarly, in cultured human aortic endothelial cells, SIRT6 knockdown increased TF mRNA, protein and activity. Moreover, SIRT6 knockdown increased mRNA levels of NF-κB-associated genes tumor necrosis factor alpha (TNF-α), poly [ADP-ribose] polymerase 1 (PARP-1), vascular cell adhesion molecule 1 (VCAM-1), and cyclooxygenase-2 (COX-2); at the protein level, COX-2, VCAM-1, TNF-α, and cleaved PARP-1 remained increased after Sirt6 knockdown. CONCLUSIONS Endothelium-specific Sirt6 deletion promotes arterial thrombosis in mice. In cultured human aortic endothelial cells, SIRT6 silencing enhances TF expression and activates pro-inflammatory pathways including TNF-α, cleaved PARP-1, VCAM-1 and COX-2. Hence, endogenous endothelial SIRT6 exerts a protective role in experimental arterial thrombosis

Elastic Wave Fields Generated by Shear Horizontal Piezoelectric Fiber Patch (SH-PFP) Transducers: Parameter Study by Modelling and Laser Vibrometric Measurements

Recently, a novel lightweight and thin piezoelectric transducer was proposed [1-3]. It generates in-plane surface tractions and thus shear horizontal elastic waves in both bulk materials and waveguides. The paper describes the principle of operation of this Shear Horizontal Piezoelectric Fiber Patch (SH-PFP). In continuation of the previous work, several variants of the SH-PFP are studied. The generated wavefield is characterized bywavefield snapshots and directivity functions. Both numerical simulation and measurements by 3D Laser Vibrometry are performed and the results are compared, showing a good agreement. We discuss possible further developments of the SH-PFP transducer to allow 1D directivity and we also discuss various possible sensor applications.</p

A novel piezoelectric fibre patch transducer for shear horizontal wave modes

Elastic waves in solids interact with scatterers and structure features, thus giving information about appearance of defects and structural changes. This is widely used in Non-destructive Testing of Materials and in Structural Health Monitoring. Relevant wave modes in isotropic bulk materials are longitudinal and shear waves which can be vertically or horizontally (with respect to the coupling surface) polarized. Guided elastic waves in plate like and pipe like structures are a superposition of several of - in general dispersive – wave modes of the Lamb wave and Shear Horizontal wave type. Horizontal polarized shear waves as the SH0 plate wave and the SH wave in isotropic solids have several advantages: they are dispersion free and don’t experience mode conversion while reflected at a backwall. For generation of SH waves, electromagnetic acoustic transducers (EMAT) are commonly used as well as piezoelectric and magnetostrictive based transducers. All these types are rather bulky and heavy, either due to the need of a backing material or to strong magnets. The paper presents a novel, lightweight and thin alternative transducer for shear horizontal elastic waves. Due to its characteristics it is most appropriate for applications where low mass and small sensor dimensions are desired. The principle of the shear horizontal (SH) wave transducer based on piezoelectric fibre patches (PFP) is described. Numerical simulation results are given for the elastic wave field in a plate generated by such an SHPFP-transducer. These results demonstrate the dominance of the SH0 mode. 3D-Laser vibrometry measurements of the wave field are in good agreement with the simulation. We discuss possible further developments of the SHPFP transducer to allow 1D directivity and we also discuss various possible sensor applications

Neurological Symptoms in Type A Aortic Dissections

Background and Purpose— Aortic dissection typically presents with severe chest or back pain. Neurological symptoms may occur because of occlusion of supplying vessels or general hypotension. Especially in pain-free dissections diagnosis can be difficult and delayed. The purpose of this study is to analyze the association between type A aortic dissection and neurological symptoms. Methods— Clinical records of 102 consecutive patients with aortic dissection (63% male, median age 58 years) over 7.5 years were analyzed for medical history, preoperative clinical characteristics, treatment and outcome with main emphasis on neurological symptoms. Results— Thirty patients showed initial neurological symptoms (29%). Only two-thirds of them reported chest pain, and most patients without initial neurological symptoms experienced pain (94%). Neurological symptoms were attributable to ischemic stroke (16%), spinal cord ischemia (1%), ischemic neuropathy (11%), and hypoxic encephalopathy (2%). Other frequent symptoms were syncopes (6%) and seizures (3%). In half of the patients, neurological symptoms were transient. Postoperatively, neurological symptoms were found in 48% of all patients encompassing ischemic stroke (14%), spinal cord ischemia (4%), ischemic neuropathy (3%), hypoxic encephalopathy (8%), nerve compression (7%), and postoperative delirium (15%). Overall mortality was 23% and did not significantly differ between patients with and without initial neurological symptoms or complications. Conclusion— Aortic dissections might be missed in patients with neurological symptoms but without pain. Neurological findings in elderly hypertensive patients with asymmetrical pulses or cardiac murmur suggest dissection. Especially in patients considered for thrombolytic therapy in acute stroke further diagnostics is essential. Neurological symptoms are not necessarily associated with increased mortality

Application of a synchrotron microprobe to the analytical characterization of ion-implanted material

A synchrotron microprobe has been used to characterize ion implantations of nickel and cobalt in silicon (100) or (111) wafers. The synchrotron radiation is collimated by means of a rigid cylindrical glass capillary of 110 mm length, 5 mm outer and 30 μm or 10 μm inner diameter. The beam is pointed at the wafer sample and the emitted radiation of X-rays is detected by an energy dispersive spectrometer. Line scans are recorded step by step over the implantation areas and across their borders. The sharpness of the borders is characterized at a lateral resolution of 13 μm and the edge lengths ranging from 0.6 to 8 mm are determined with an accuracy better than ± 20 μm. The signal intensity and implantation dose of cobalt ranging from 1 × 1015 to 1 × 1017 ions cm−2 show a linear relationship as is to be expected for the micrometre thin implanted layers