2,464 research outputs found
Quantum limited particle sensing in optical tweezers
Particle sensing in optical tweezers systems provides information on the
position, velocity and force of the specimen particles. The conventional
quadrant detection scheme is applied ubiquitously in optical tweezers
experiments to quantify these parameters. In this paper we show that quadrant
detection is non-optimal for particle sensing in optical tweezers and propose
an alternative optimal particle sensing scheme based on spatial homodyne
detection. A formalism for particle sensing in terms of transverse spatial
modes is developed and numerical simulations of the efficacy of both quadrant
and spatial homodyne detection are shown. We demonstrate that an order of
magnitude improvement in particle sensing sensitivity can be achieved using
spatial homodyne over quadrant detection.Comment: Submitted to Biophys
Origin of ferromagnetism in (Zn,Co)O from magnetization and spin-dependent magnetoresistance
In order to elucidate the nature of ferromagnetic signatures observed in
(Zn,Co)O we have examined experimentally and theoretically magnetic properties
and spin-dependent quantum localization effects that control low-temperature
magnetoresistance. Our findings, together with a through structural
characterization, substantiate the model assigning spontaneous magnetization of
(Zn,Co)O to uncompensated spins at the surface of antiferromagnetic nanocrystal
of Co-rich wurtzite (Zn,Co)O. The model explains a large anisotropy observed in
both magnetization and magnetoresistance in terms of spin hamiltonian of Co
ions in the crystal field of the wurtzite lattice.Comment: 6 pages, 6 figure
Functional conservation of a forebrain enhancer from the elephant shark (Callorhinchus milii) in zebrafish and mice
Background: The phylogenetic position of the elephant shark (Callorhinchus milii ) is particularly relevant to study the evolution of genes and gene regulation in vertebrates. Here we examine the evolution of Dlx homeobox gene regulation during vertebrate embryonic development with a particular focus on the forebrain. We first identified the elephant shark sequence orthologous to the URE2 cis -regulatory element of the mouse Dlx1/Dlx2 locus (herein named CmURE2). We then conducted a comparative study of the sequence and enhancer activity of CmURE2 with that of orthologous regulatory sequences from zebrafish and mouse.
Results: The CmURE2 sequence shows a high percentage of identity with its mouse and zebrafish counterparts but is overall more similar to mouse URE2 (MmURE2) than to zebrafish URE2 (DrURE2). In transgenic zebrafish and mouse embryos, CmURE2 displayed enhancer activity in the forebrain that overlapped with that of DrURE2 and MmURE2. However, we detected notable differences in the activity of the three sequences in the diencephalon. Outside of the forebrain, CmURE2 shows enhancer activity in areas such as the pharyngeal arches and dorsal root ganglia where its' counterparts are also active.
Conclusions: Our transgenic assays show that part of the URE2 enhancer activity is conserved throughout jawed vertebrates but also that new characteristics have evolved in the different groups. Our study demonstrates that the elephant shark is a useful outgroup to study the evolution of regulatory mechanisms in vertebrates and to address how changes in the sequence of cis -regulatory elements translate into changes in their regulatory activity
Preoperative Kidney Function linked to mortality and readmission outcomes at Day 90 and 30 in Older Emergency Surgical Patients
Grants were received from British Geriatric Society and The Renal Association to support Louis EvansPeer reviewedPublisher PD
Kajian Kandungan Radioisotop Alam dalam Sampel Batuan di Desa Oben Baun Kupang Barat dengan Teknik Analisis Radioaktivitas Lingkungan
Masalah pokok yang dikaji dalam penelitian ini adalah pemetaan dan analisis aktivitas jenis massa kandungan radioisotop dalam deposit mineral di Desa Oben Baun Kupang Barat. Tujuan Penelitian meliputi: menentukan kisaran cacah radiasi radioisotop alam di beberapa titik pengukuran di lapangan dan pengukuran di laboratorium, menentukan kisaran aktivitas jenis massa (C) kandungan radioisotop dalam sampel batuan, memetakan sebaran cacah dan aktivitas jenis massa radioisotop pada luasan daerah tertentu yang terjangkau survei di lapangan, dan mengestimasi tingkat kontaminasi radioaisotop pada lingkungan. Metode penelitian meliputi: observasi/ survei, mapping, sampling, analisis, interpretasi. Hasil-hasil penelitian: Kisaran cacah radiasi nuklir radioisotop di lapangan dan dilaboratorium dalam deposit mineral di Oben Baun Kupang Barat berturut-turut berkisar antara 15 cpm sampai dengan 93 cpm dan 28 cpm sampai dengan 92 cpm. Kisaran aktivitas jenis massa (C) kandungan radioisotop dalam 45 cuplikan sampel batuan di Oben Baun Kupang Barat berkisar antara 0,099 x 10-5 µCi/gram sampai dengan 0,316 x 10-5 µCi/gram. Sebaran atau distribusi kandungan radioisotop di Desa Oben Baun Kupang Barat yang dapat dijangkau survei terdistribusi lebih tinggi dari arah timur dan cenderung menurun ke arah barat. Distribusi tersebut masih cenderung tinggi ke arah utara di bagian timur lokasi survei. Kontaminasi radioisotop pada lingkungan masih tergolong kontaminasi rendah untuk radiasi alpha dan beta, dan secara umum cacah radiasi radioisotop di lapangan masih bersesuaian dengan batas toleransi, walaupun perlu diwaspadai beberapa titik ukur dengan cacah radiasi melebihi standar.
Kata Kunci: Radioisotop, Aktivitas Jenis Massa, Daerah Kontaminasi.  
The role of tank-treading motions in the transverse migration of a spheroidal vesicle in a shear flow
The behavior of a spheroidal vesicle, in a plane shear flow bounded from one
side by a wall, is analysed when the distance from the wall is much larger than
the spheroid radius. It is found that tank treading motions produce a
transverse drift away from the wall, proportional to the spheroid eccentricity
and the inverse square of the distance from the wall. This drift is independent
of inertia, and is completely determined by the characteristics of the vesicle
membrane. The relative strength of the contribution to drift from tank-treading
motions and from the presence of inertial corrections, is discussed.Comment: 16 pages, 1 figure, Latex. To appear on J. Phys. A (Math. Gen.
Chinese and African migrant entrepreneur's articulation shaped by African agency
Much has been written on the relationship of China and Africa in the past decade. However, the subject of Chinese migrant entrepreneurs in Africa and their articulation with African counterparts was little explored up to the early 2010s. Apparently, this research gap has been closed, as shown by four publications in recent years: three edited volumes and one monography, focusing on this subject. In view of early prejudices on the passive or even disapproving reception of Chinese migrants by Africans, the state of the art underlines the importance and scope of African agency vis à vis Chinese migrant entrepreneurs in Africa. This has been underlined unison in the four books under review. Book review of:(1) Giese, Karsten, Marfaing, Laurence (eds) (2016): Entrepreneurs Africains et Chinois. Les impacts sociaux d’une rencontre particulière. Paris: Karthala. (2) Gadzala, Aleksandra W. (ed) (2015): Africa and China: how Africans and their governments are shaping relations with China. Lanham/Md.: Rowman & Littlefield. (3) Mohan, Giles, Lampert, Ben et al (eds) (2014): Chinese Migrants and Africa's Development: new imperialists or agents of change? London: Zed books. (4) French, Howard W. (2015): China's Second Continent: how a million migrants are building a new empire in Africa. London: Penguin Random House / New York: Knopf.On a beaucoup écrit sur la relation entre la Chine et l'Afrique dans la dernière décennie. Cependant, le sujet des entrepreneurs migrants chinois en Afrique et leur articulation avec leurs homologues africains a été peu exploré jusqu'au début des années 2010. Apparemment, cet écart de recherche a été fermé, comme indiqué par quatre publications au cours des dernières années: trois volumes édités et une monographie, en se concentrant sur ce sujet. Compte tenu des premiers préjugés sur la réception passive ou même désapprobateur des migrants chinois par les Africains, l'état de l'art souligne l'importance et la portée de l'agence africaine vis-à-vis des entrepreneurs migrants chinois en Afrique
- …