Time-dependent speckle in holographic optical coherence imaging and the health of tumor tissue

Holographic optical coherence imaging acquires en face images from successive depths inside scattering tissue. In a study of multicellular tumor spheroids the holographic features recorded from a fixed depth are observed to be time dependent, and they may be classified as variable or persistent. The ratio of variable to persistent features, as well as speckle correlation times, provides quantitative measures of the health of the tissue. Studies of rat osteogenic sarcoma tumor spheroids that have been subjected to metabolic and cross-polymerizing poisons provide quantitative differentiation among healthy, necrotic, and poisoned tissue. Organelle motility in healthy tissue appears as super-Brownian laser speckle, whereas chemically fixed tissue exhibits static speckle.     

Electrical and Spectral Characteristics of a Heated Cathode Discharge in Metal Vapors

A new type of discharge in pure metal vapors like copper or titanium is described. A stable discharge is produced between a heated cathode and the anode which has a melted spot on its surface due to the electron bombardment. The spectral characteristics prove that the discharge take place in the vapors of the anode material continuously evaporated from the melted spot on the anode. The discharge has a similar behaviour as the low voltage arc.     

Rheological testing of p-tert-butylphenol epoxy–acrylic resin in the presence of reactive diluents

The rheological testing of synthesized para-tert-butylphenol epoxy–acrylic resin in the presence of reactive diluents based on epoxy–acrylic compounds of phenol, para-tert-butylphenol and para-nonylphenol was carried out with a “Rheotest 2” type viscometer. The synthesized resin, the tested reactive diluents, as well as the mixtures based on the resin and the reactive diluents, show non-Newtonian rheological behaviour of the pseudoplastic type. This behaviour can be explained by taking into consideration the possible interactions among the chains of the phenolic reactive diluents, and with the chain of the resin. These interactions can also be due to –OH phenolic groups. As a result, a false increase is registered in the molecular weight of the systems studied.     

The multiplier ideals of a sum of ideals

We prove that if , are nonzero sheaves of ideals on a complex smooth variety , then for every we have the following relation between the multiplier ideals of , and :

A similar formula holds for the asymptotic multiplier ideals of the sum of two graded systems of ideals.

We use this result to approximate at a given point arbitrary multiplier ideals by multiplier ideals associated to zero dimensional ideals. This is applied to compare the multiplier ideals associated to a scheme in different embeddings.

     

Design of quantum dot-conjugated lipids for long-term, high-speed tracking experiments on cell surfaces

The current study reports the facile design of quantum dot (QD)-conjugated lipids and their application to high-speed tracking experiments on cell surfaces. CdSe/ZnS core/shell QDs with two types of hydrophilic coatings, 2-(2-aminoethoxy)ethanol (AEE) and a 60:40 molar mixture of 1,2-dipalmitoyl- sn-glycero-3-phosphocholine and 1,2-dipalmitoyl- sn-glycero-3-phosphoethanolamine- N-[methoxy(polyethylene glycol-2000], are conjugated to sulfhydryl lipids via maleimide reactive groups on the QD surface. Prior to lipid conjugation, the colloidal stability of both types of coated QDs in aqueous solution is confirmed using fluorescence correlation spectroscopy. A sensitive assay based on single lipid tracking experiments on a planar solid-supported phospholipid bilayer is presented that establishes conditions of monovalent conjugation of QDs to lipids. The QD-lipids are then employed as single-molecule tracking probes in plasma membranes of several cell types. Initial tracking experiments at a frame rate of 30 frames/s corroborate that QD-lipids diffuse like dye-labeled lipids in the plasma membrane of COS-7, HEK-293, 3T3, and NRK cells, thus confirming monovalent labeling. Finally, QD-lipids are applied for the first time to high-speed single-molecule imaging by tracking their lateral mobility in the plasma membrane of NRK fibroblasts with up to 1000 frames/s. Our high-speed tracking data, which are in excellent agreement with previous tracking experiments that used larger (40 nm) Au labels, not only push the time resolution in long-time, continuous fluorescence-based single-molecule tracking but also show that highly photostable, photoluminescent nanoprobes of 10 nm size can be employed (AEE-coated QDs). These probes are also attractive because, unlike Au nanoparticles, they facilitate complex multicolor experiments.