Towards efficient modelling of optical micromanipulation of complex structures

Computational methods for electromagnetic and light scattering can be used for the calculation of optical forces and torques. Since typical particles that are optically trapped or manipulated are on the order of the wavelength in size, approximate methods such as geometric optics or Rayleigh scattering are inapplicable, and solution or either the Maxwell equations or the vector Helmholtz equation must be resorted to. Traditionally, such solutions were only feasible for the simplest geometries; modern computational power enable the rapid solution of more general--but still simple--geometries such as axisymmetric, homogeneous, and isotropic scatterers. However, optically-driven micromachines necessarily require more complex geometries, and their computational modelling thus remains in the realm of challenging computational problems. We review our progress towards efficient computational modelling of optical tweezers and micromanipulation, including the trapping and manipulation of complex structures such as optical micromachines. In particular, we consider the exploitation of symmetry in the modelling of such devices.Comment: 5 pages, 4 figure

Modelling optical micro-machines

A strongly focused laser beam can be used to trap, manipulate and exert torque on a microparticle. The torque is the result of transfer of angular momentum by scattering of the laser beam. The laser could be used to drive a rotor, impeller, cog wheel or some other microdevice of a few microns in size, perhaps fabricated from a birefringent material. We review our methods of computationally simulating the torque and force imparted by a laser beam. We introduce a method of hybridizing the T-matrix with the Finite Difference Frequency Domain (FDFD) method to allow the modelling of materials that are anisotropic and inhomogeneous, and structures that have complex shapes. The high degree of symmetry of a microrotor, such as discrete or continuous rotational symmetry, can be exploited to reduce computational time and memory requirements by orders of magnitude. This is achieved by performing calculations for only a given segment or plane that is repeated across the whole structure. This can be demonstrated by modelling the optical trapping and rotation of a cube.Comment: 4 pages, 3 figure

Reflections, Resilience, and Recovery: A qualitative study of the COVID-19 impact on an international general population’s mental health and priorities for support

The impact of the coronavirus 2019 (COVID-19) pandemic on different countries and populations is well documented in quantitative studies, with some studies showing stable mental health symptoms and others showing fluctuating symptoms. However, the reasons behind why some symptoms are stable and others change are under-explored, which in turn makes identifying the types of support needed by participants themselves challenging. To address these gaps, this study thematically analysed 925 qualitative responses from five open-ended responses collected in the UCL-Penn Global COVID Study between 17 April to 31 July 2021 (wave 3). Three key themes comprised of 13 codes were reported by participants across countries and ages regarding the impact of COVID-19 on their health, both mental and physical, and livelihoods. These include: 1) Outlook on self/life, 2) Self-improvement, and 3) Loved ones (friends and family). In terms of support, while 2.91% did not require additional support, 91% wanted support beyond financial. Other unexpected new themes were also discussed regarding vulnerable populations suffering disproportionately. The pandemic has brought into sharp focus various changes in people’s mental health, physical health, and relationships. Greater policy considerations should be given to supporting citizens’ continued access to mental health when considering pandemic recovery

Quality of life measurement in women with cervical cancer: implications for Chinese cervical cancer survivors

<p>Abstract</p> <p>Background</p> <p>Women with cervical cancer now have relatively good 5-year survival rates. Better survival rates have driven the paradigm in cancer care from a medical illness model to a wellness model, which is concerned with the quality of women's lives as well as the length of survival. Thus, the assessment of quality of life among cervical cancer survivors is increasingly paramount for healthcare professionals. The purposes of this review were to describe existing validated quality of life instruments used in cervical cancer survivors, and to reveal the implications of quality of life measurement for Chinese cervical cancer survivors.</p> <p>Methods</p> <p>A literature search of five electronic databases was conducted using the terms <it>cervical/cervix cancer</it>, <it>quality of life</it>, <it>survivors</it>, <it>survivorship</it>, <it>measurement</it>, and <it>instruments</it>. Articles published in either English or Chinese from January 2000 to June 2009 were searched. Only those adopting an established quality of life instrument for use in cervical cancer survivors were included.</p> <p>Results</p> <p>A total of 11 validated multidimensional quality of life instruments were identified from 41 articles. These instruments could be classified into four categories: generic, cancer-specific, cancer site-specific and cancer survivor-specific instruments. With internal consistency varying from 0.68-0.99, the test-retest reliability ranged from 0.60-0.95 based on the test of the Pearson coefficient. One or more types of validity supported the construct validity. Although all these instruments met the minimum requirements of reliability and validity, the original versions of these instruments were mainly in English.</p> <p>Conclusion</p> <p>Selection of an instrument should consider the purpose of investigation, take its psychometric properties into account, and consider the instrument's origin and comprehensiveness. As quality of life can be affected by culture, studies assessing the quality of life of cervical cancer survivors in China or other non-English speaking countries should choose or develop instruments relevant to their own cultural context. There is a need to develop a comprehensive quality of life instrument for Chinese cervical cancer survivors across the whole survivorship, including immediately after diagnosis and for short- (less than 5 years) and long-term (more than 5 years) survivorship.</p