Nanometric depth resolution from multi-focal images in microscopy

We describe a method for tracking the position of small features in three dimensions from images recorded on a standard microscope with an inexpensive attachment between the microscope and the camera. The depth-measurement accuracy of this method is tested experimentally on a wide-field, inverted microscope and is shown to give approximately 8 nm depth resolution, over a specimen depth of approximately 6 µm, when using a 12-bit charge-coupled device (CCD) camera and very bright but unresolved particles. To assess low-flux limitations a theoretical model is used to derive an analytical expression for the minimum variance bound. The approximations used in the analytical treatment are tested using numerical simulations. It is concluded that approximately 14 nm depth resolution is achievable with flux levels available when tracking fluorescent sources in three dimensions in live-cell biology and that the method is suitable for three-dimensional photo-activated localization microscopy resolution. Sub-nanometre resolution could be achieved with photon-counting techniques at high flux levels.     

Quantum dot/plasmonic nanoparticle metachromophores with quantum yields that vary with excitation wavelength

Coupled plasmonic/chromophore systems are of interest in applications ranging from fluorescent biosensors to solar photovoltaics and photoelectrochemical cells because near-field coupling to metal nanostructures can dramatically alter the optical performance of nearby materials. We show that CdSe quantum dots (QDs) near single silver nanoprisms can exhibit photoluminescence lifetimes and quantum yields that depend on the excitation wavelength, in apparent violation of the Kasha-Vavilov rule. We attribute the variation in QD lifetime with excitation wavelength to the wavelength-dependent coupling of higher-order plasmon modes to different spatial subpopulations of nearby QDs. At the QD emission wavelength, these subpopulations are coupled to far-field radiation with varying efficiency by the nanoprism dipolar resonance. These results offer an easily accessible new route to design metachromophores with tailored optical properties.     

Quantum‐Hall to Insulator Transition in Ultra‐Low‐Carrier‐Density Topological Insulator Films and a Hidden Phase of the Zeroth Landau Level

A key feature of the topological surface state under a magnetic field is the presence of the zeroth Landau level at the zero energy. Nonetheless, it is challenging to probe the zeroth Landau level due to large electron–hole puddles smearing its energy landscape. Here, by developing ultra‐low‐carrier density topological insulator Sb₂Te₃ films, an extreme quantum limit of the topological surface state is reached and a hidden phase at the zeroth Landau level is uncovered. First, an unexpected quantum‐Hall‐to‐insulator‐transition near the zeroth Landau level is discovered. Then, through a detailed scaling analysis, it is found that this quantum‐Hall‐to‐insulator‐transition belongs to a new universality class, implying that the insulating phase discovered here has a fundamentally different origin from those in nontopological systems.     

Impaired liver function tests in patients treated with antithymocyte globulin: implication for liver transplantation

Antithymocyte globulin (ATG) is traditionally used as a conventional immunosuppression agent in various pathological states including severe aplastic anaemia (SAA), graft versus host disease (GVHD), and for the prevention and treatment of graft rejection and GVHD post bone marrow and liver transplantation. We reviewed the liver functions of 16 haematological patients with no previous liver disorders who received ATG as part of their pre-bone marrow transplantation (BMT) conditioning regimen, and the liver function tests of five SAA patients who received ATG as part of their treatment. Liver functions were evaluated at day -1 pre-, and days +3 and +10 post-ATG treatment. All patients had normal liver functions before treatment. In the haematological patients, the mean serum lactic dehydrogenase (LDH) levels increased from 408.7 +/- 37.7 U/l pre-treatment to 1394.4 +/- 488.7 U/l 3 days post-treatment (n = 16; p < 0.029), and then declined to 561.4 +/- 61.3 U/l 10 days post-treatment (n = 16; p < 0.043). The mean alanine aminotransferase (ALT) levels increased from 51.9 +/- 11.3 U to 184.6 +/- 74.6 U (n = 16; p < 0.036), and then declined to 121.9 +/- 61.3 U (n = 16; NS). The mean aspartate amino transferase (AST) levels increased from 31.2 + 5.7 U to 152.0 +/- 67.0 U (n = 16; p < 0.44) and then declined to 46.0 +/- 14 (n = 16; p < 0.049). The mean tau-glutamyltransferase (GTP) levels increased from 93.0 +/- 34 to 188.0 +/- 36 (n = 16; p < 0.02), and were 168.0 +/- 37.0 at day +10 (n = 16; NS). The mean bilirubin levels increased from 18.0 +/- 1.9 microM l(-1) to 22.7 +/- 2.8 (n = 16); NS), at day +3 and to 31.9 +/- 6.9 at day +10 (n = 16; NS). In contrast, no significant changes in liver function tests were demonstrated in the SAA patients treated with ATG. The possible pathophysiologic mechanisms and the clinical implications for liver transplantation are discussed.     

Anatomy of a nanoscale conduction channel reveals the mechanism of a high-performance memristor

By employing a precise method for locating and directly imaging the active switching region in a resistive random access memory (RRAM) device, a nanoscale conducting channel consisting of an amorphous Ta(O) solid solution surrounded by nearly stoichiometric Ta(2) O(5) is observed. Structural and chemical analysis of the channel combined with temperature-dependent transport measurements indicate a unique resistance switching mechanism.     

Testing Periodicity

We study the string-property of being periodic and having periodicity smaller than a given bound. Let Σ be a fixed alphabet and let p,n be integers such that p ￡ \fracn2p\leq \frac{n}{2} . A length-n string over Σ, α=(α ₁,…,α _n ), has the property Period(p) if for every i,j∈{1,…,n}, α _i =α _j whenever i≡j (mod p). For an integer parameter g ￡ \fracn2,g\leq \frac{n}{2}, the property Period(≤g) is the property of all strings that are in Period(p) for some p≤g. The property Period( ￡ \fracn2)\mathit{Period}(\leq \frac{n}{2}) is also called Periodicity.     

The Meaning of ‘Build Back Better’: Evidence From Post‐Tsunami Aceh and Sri Lanka

The 26 December 2004 tsunami disaster around the Indian Ocean provided an opportunity to see if decades of knowledge and experience on post‐disaster settlement and shelter could be applied to match the tagline which many groups gave to the post‐tsunami reconstruction: ‘build back better’ (or ‘building back better’). This paper uses evidence from field work completed on implementing settlement and shelter in post‐tsunami Aceh and Sri Lanka to examine whether or not the theory and practice of ‘build back better’ were witnessed. Focusing on settlement and shelter, four areas are examined: (i) safety, security, and livelihoods; (ii) how post‐disaster settlement and shelter could have an improved connection with permanent housing and communities (the ‘transition to what?’ question); (iii) fairness and equity; and (iv) connecting relief and development by tackling root causes of vulnerability. Based on the field work, addressing these four areas is suggested as how ‘build back better’ could be implemented. Recommendations are

• 1 Community involvement is essential, but that does not necessarily mean community control.
• 2 Organizations involved in implementing transitional settlement and shelter need to consider their capacity and links to other sectors.
• 3 Thinking ahead is necessary by integrating relief and development through long‐term planning and disaster risk reduction.

Overall, ‘building back safer’ might be a preferable tagline to ‘building back better’ because ‘better’ has multiple interpretations, many of which caused further problems, whereas ‘safer’ provides a clearer goal on which to focus for post‐disaster settlement and shelter.     

Requirement for homologous rabbit reticulocyte initiation factor 3 for initiation of alpha- and beta-globin mRNA translation in a crude protozoal cell-free system

Experimental evidence showing specificity of rabbit reticulocyte initiation factor 3 (EIF-3) for selective initiation of mRNA translation is presented. A new cell-free system was developed from Crithidia fasciculata. The crude postmitochondrial supernatant fluid was treated with puromycin and 0.5 M KCl to dissociate mRNA from polysomes and ribosomes into subunits. The drug and salt were removed by gel filtration on Sephadex G-25. Additions of amino acids and energy source initiate protein synthesis. All synthesis starts at the initiation site. This treatment brought about a shift in MgCl2 optimum from 6 to 3 mM. Exogenously supplied rabbit reticulocyte globin mRNA is faithfully translated in this system. However, crithidial EIF-3 has a low affinity for globin mRNA as evidenced by a 6-fold increase in the rate of globin synthesis after the addition of rabbit reticulocyte EIF-3 in the range at which globin synthesis is linear to the amount of globin mRNA added to the system. It is also shown that in a reconstituted system in which ribosomal subunits are depleted from initiation factors, EIF-3 from rabbit reticulocytes has a higher affinity for globin mRNA, as measured by the formation of polysomes during the linear time of amino acid incorporation. These results are taken to indicate that initiation factor EIF-3 action should be considered as an enzyme catalyzed reaction for which various mRNAs serve as different substrate analogs. Therefore, specificity is most likely to be expressed as an affinity of enzyme to substrate and would show as rate difference rather than an all-or-none phenomenon.     

The Choice of Manufacturing Technology in the Presence of Dynamic Demand and Experience Effects

This study investigates the intertemporal manufacturing policy of a firm faced with dynamic demand conditions and experience effects in production. We consider a demand structure characterized by a Mansfield-like product diffusion process and examine two manufacturing processes: a low-volume, high-variable, low-fixed cost function, and a high-volume, low-variable, high-fixed cost function. An investment and production model that incorporates these tradeoffs is formulated and analyzed as a two-phase optimal control problem. The major findings relate to the production rate, the duration of each manufacturing phase, and the switching policies from one phase to the other. Illustrations of the methodology are provided and. discussed.