Qualitative feature of the low-lying spectrum of intrashell states of 4-valence-electron atoms derived from symmetry consideration

Inherent nodal surfaces existing in the wavefunctions of intrashell states of 4-valence-electron atoms have been investigated. The decisive effect of these surfaces has been demonstrated, the ordering of low-lying levels has been predicted, a primary classification scheme has been proposed, the existence of three rotation bands has been suggested.Comment: 10 pages, no figure

Improving light delivery for optogenetics using wavefront shaping

New developments in neuroscience are enabling us to understand the brain at unprecedented temporal and spatial resolution. One of these exciting new techniques is optogenetics, which allows select neuronal populations of the brain to be targeted to express light sensitive ion channels. These enable optical control of the electrophysiological state of the cell, enabling neurons to be activated or deactivated using light. However, due to the strongly scattering nature of biological tissue in the brain, tightly focusing light to a specific voxel is not possible with conventional optical techniques. In this poster we will present the results of our recent work to develop new optical wavefront shaping tools which enable us to focus light inside strongly scattering media and discuss the outlook for such tools for improving light delivery for techniques such as optogenetics. The focus of our work is to use an optical wavefront shaping technology termed Time-Reversed Ultrasound- Encoded (TRUE) focusing [1,2]. This strategy uses ultrasound to form an ultrasonic focus at depths beyond the optical diffusion limit. This ultrasound focus modulates photons passing through it via the acousto-optic effect, shifting their frequency by the ultrasound frequency. Then, by detecting these ultrasound-tagged photons, we can measure the optical wavefront corresponding to the tagged photons and selectively time-reverse this optical field using a technique called Digital Optical Phase Conjugation (DOPC) [3]. This wavefront is then used to send photons back into the scattering tissue in such a way that they travel in a time-reversed fashion, constructively interfering at the location of the ultrasound focus. This allows us to focus light in highly scattering media beyond the optical diffusion limit at ultrasonic resolution (~30 micrometers at 50 MHz). In this poster we will present results from recent work using the TRUE focusing technique to perform optogenetic stimulation. We demonstrate in 300 and 500 micrometer thick living brain slices that the TRUE focusing technique can be used to improve the spatial resolution of optogenetic stimulation compared to conventional optical methods. Furthermore, we will discuss the outlook and challenges facing the development of wavefront shaping techniques such as TRUE focusing for applications in neuroscience and other areas of biotechnology. References: [1] Xu, Xiao, Honglin Liu, and Lihong V. Wang. Time-reversed ultrasonically encoded optical focusing into scattering media. Nature photonics 5.3 (2011): 154-157. [2] Wang, Ying Min, et al. Deep-tissue focal fluorescence imaging with digitally time-reversed ultrasound- encoded light. Nature communications 3 (2012): 928. [3] Cui, Meng, and Changhuei Yang. Implementation of a digital optical phase conjugation system and its application to study the robustness of turbidity suppression by phase conjugation. Optics express 18.4 (2010)

Time-reversed ultrasonically encoded (TRUE) focusing for deep-tissue optogenetic modulation

The problem of optical scattering was long thought to fundamentally limit the depth at which light could be focused through turbid media such as fog or biological tissue. However, recent work in the field of wavefront shaping has demonstrated that by properly shaping the input light field, light can be noninvasively focused to desired locations deep inside scattering media. This has led to the development of several new techniques which have the potential to enhance the capabilities of existing optical tools in biomedicine. Unfortunately, extending these methods to living tissue has a number of challenges related to the requirements for noninvasive guidestar operation, speed, and focusing fidelity. Of existing wavefront shaping methods, time-reversed ultrasonically encoded (TRUE) focusing is well suited for applications in living tissue since it uses ultrasound as a guidestar which enables noninvasive operation and provides compatibility with optical phase conjugation for high-speed operation. In this paper, we will discuss the results of our recent work to apply TRUE focusing for optogenetic modulation, which enables enhanced optogenetic stimulation deep in tissue with a 4-fold spatial resolution improvement in 800-micron thick acute brain slices compared to conventional focusing, and summarize future directions to further extend the impact of wavefront shaping technologies in biomedicine

Deep tissue optical focusing and optogenetic modulation with time-reversed ultrasonically encoded light

Noninvasive light focusing deep inside living biological tissue has long been a goal in biomedical optics. However, the optical scattering of biological tissue prevents conventional optical systems from tightly focusing visible light beyond several hundred micrometers. The recently developed wavefront shaping technique time-reversed ultrasonically encoded (TRUE) focusing enables noninvasive light delivery to targeted locations beyond the optical diffusion limit. However, until now, TRUE focusing has only been demonstrated inside nonliving tissue samples. We present the first example of TRUE focusing in 2-mm-thick living brain tissue and demonstrate its application for optogenetic modulation of neural activity in 800-μm-thick acute mouse brain slices at a wavelength of 532 nm. We found that TRUE focusing enabled precise control of neuron firing and increased the spatial resolution of neuronal excitation fourfold when compared to conventional lens focusing. This work is an important step in the application of TRUE focusing for practical biomedical uses

The Histone Deacetylase Inhibitor Romidepsin Spares Normal Tissues While Acting as an Effective Radiosensitizer in Bladder Tumors in Vivo

Funding Information: This work was funded by Cancer Research UK (CRUK; C5255/A23755). J.L.R. was funded by CRUK (project grant C15140/A19817). C.K.T. was funded by a CRUK DPhil Research Training and Support Grant, the Balliol College Alfred Douglas Stone Scholarship, and the University of Oxford Clarendon Fund. S.K. was funded by a CRUK/MRC Oxford Institute of Radiation Oncology CRUK studentship.Peer reviewedPublisher PD

Oat-based milk alternatives: the influence of physical and chemical properties on the sensory profile

Oat-based milk alternatives (OMAs) have become increasingly popular, perhaps due to their low allergenicity and preferred sensory attributes when compared to other milk alternatives. They may also provide health benefits from unique compounds; avenanthramides, avenacosides, and the dietary fibre beta-glucan. This has led to a variety of commercial options becoming available. Being a fairly new product, in comparison to other plant-based milk alternatives (PBMAs), means little research has been undertaken on the sensory profile, and how it is influenced by the physical and chemical properties

Time-reversed ultrasonically encoded (TRUE) focusing for deep-tissue optogenetic modulation

The problem of optical scattering was long thought to fundamentally limit the depth at which light could be focused through turbid media such as fog or biological tissue. However, recent work in the field of wavefront shaping has demonstrated that by properly shaping the input light field, light can be noninvasively focused to desired locations deep inside scattering media. This has led to the development of several new techniques which have the potential to enhance the capabilities of existing optical tools in biomedicine. Unfortunately, extending these methods to living tissue has a number of challenges related to the requirements for noninvasive guidestar operation, speed, and focusing fidelity. Of existing wavefront shaping methods, time-reversed ultrasonically encoded (TRUE) focusing is well suited for applications in living tissue since it uses ultrasound as a guidestar which enables noninvasive operation and provides compatibility with optical phase conjugation for high-speed operation. In this paper, we will discuss the results of our recent work to apply TRUE focusing for optogenetic modulation, which enables enhanced optogenetic stimulation deep in tissue with a 4-fold spatial resolution improvement in 800-micron thick acute brain slices compared to conventional focusing, and summarize future directions to further extend the impact of wavefront shaping technologies in biomedicine

Large strain compressive response of 2-D periodic representative volume element for random foam microstructures

A numerical investigation has been conducted to determine the influence of Representative Volume Element (RVE) size and degree of irregularity of polymer foam microstructure on its compressive mechanical properties, including stiffness, plateau stress and onset strain of densification. Periodic two-dimensional RVEs have been generated using a Voronoi-based numerical algorithm and compressed. Importantly, self-contact of the foam’s internal microstructure has been incorporated through the use of shell elements, allowing simulation of the foam well into the densification stage of compression; strains of up to 80 percent are applied. Results suggest that the stiffness of the foam RVE is relatively insensitive to RVE size but tends to soften as the degree of irregularity increases. Both the shape of the plateau stress and the onset strain of densification are sensitive to both the RVE size and degree of irregularity. Increasing the RVE size and decreasing the degree of irregularity both tend to result in a decrease of the gradient of the plateau region, while increasing the RVE size and degree of irregularity both tend to decrease the onset strain of densification. Finally, a method of predicting the onset strain of densification to an accuracy of about 10 per cent, while reducing the computational cost by two orders of magnitude is suggested