Non-invasive imaging of human skin and human skin tissues by optical coherence tomography (OCT) is a field exciting a great deal of interest especially in terms of day-to-day medical and biomedical diagnostics. We develop rapid scanning OCT system for non-invasive real-time imaging of topical skin tissues in vivo. We investigate the possibility of OCT image enhancement along the transcutaneous diffusion into the skin an optical clearing agent. Diffusion of optical clearing agents, e.g. such as glycerol, temporary increases transparency of topical skin tissues that allows for unrestricted sounding radiation permeating deeper into the skin. Increasing transparency of superficial skin tissues significantly improves depth of imaging, image contrast and spatial resolution. Thus, topical optical clearing of skin enable applying low power light source (0.5 -0.2 mW) and achieve the probing depth up to 1.5 -1.7 mm. Current approach is able providing images of superficial human blood vessels 0.2 -1 mm in diameter that are not visible by conventional OCT at normal conditions. The presented results illustrate, for the first time of our knowledge, the images of topical skin vessels with 12 µm spatial resolution before and after optical clearing.OCT image (2 × 2 mm) of subcutaneous blood vessel in human skin in vivo after 20 minutes of optical clearing
In recent years, time-resolved spectroscopy systems using near infrared pulsed laser have been applied to develop optical computed tomography. We applied this technique to measure the optical properties of osseous tissue. First, we gradually demineralized 10 mm blocks of bovine trabecular bone with EDTA, maintaining the absorption characteristics and structure but varying the hydroxyapatite content, thus creating specimens differing only in light scattering properties. We used computer densitograms to assess light penetration, and analyzed the correlation with bone mineral density (BMD) as with dual-energy X-ray absorptiometry scans. The light penetration increased with decreasing BMD. Second, using the above-mentioned pulsed laser time-resolved spectroscopy system, we investigated the correlation between the BMD and the time response
Absorption coel~cient measurements of strongly scattering and weakly absorbing media have been performed using time resolved transmittance of a 100 fs pulse through a 30 mm slab containing latex spheres suspended in water and absorbing ink solutions. The scattering and absorption coefficients were selected so that the optical properties of the media were similar to those of biological tissues. Measured curves of time-resolved transmittance of the pulse through the media were used to estimate the optical properties of the media. The experiment was made at two different wavelengths, 784 nm and 810 nm. Estimated absorption coefficients were in gcod agreement with those measured in a nonscattering case by a spectrophotometer.
Attackers leverage memory corruption vulnerabilities to establish primitives for reading from or writing to the address space of a vulnerable process. These primitives form the foundation for code-reuse and data-oriented attacks. While various defenses against the former class of attacks have proven effective, mitigation of the latter remains an open problem. In this paper, we identify various shortcomings of the x86 architecture regarding memory isolation, and leverage virtualization to build an effective defense against data-oriented attacks. Our approach, called xMP, provides (in-guest) selective memory protection primitives that allow VMs to isolate sensitive data in user or kernel space in disjoint xMP domains. We interface the Xen altp2m subsystem with the Linux memory management system, lending VMs the flexibility to define custom policies. Contrary to conventional approaches, xMP takes advantage of virtualization extensions, but after initialization, it does not require any hypervisor intervention. To ensure the integrity of in-kernel management information and pointers to sensitive data within isolated domains, xMP protects pointers with HMACs bound to an immutable context, so that integrity validation succeeds only in the right context. We have applied xMP to protect the page tables and process credentials of the Linux kernel, as well as sensitive data in various user-space applications. Overall, our evaluation shows that xMP introduces minimal overhead for real-world workloads and applications, and offers effective protection against data-oriented attacks.
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