Synchronized, continuous-flow zone electrophoresis

A new method for performing continuous electrophoretic separation of complex mixtures in microscale devices is proposed. Unlike in free-flow electrophoresis devices, no mechanical pumping is requiredboth fluid transport and separation are driven electrokinetically. This gives the method great potential for on-a-chip integration in multistep analytical systems. The method enables us to collect fractionated sample and tensfold purification is possible. The model of the operation is presented and a detailed description of the optimal conditions for performing purification is given. The chip devices with 10-μm-deep separation chamber of 1.5 mm × 4 mm in size were fabricated in glass. A standard microchip electrophoresis setup was used. Continuous separation of rhodamine B, rhodamine 6G, and fluorescein was accomplished. Purification was demonstrated on a mixture containing rhodamine B and fluorescein, and the recovery of both fractions was achieved. The results show the feasibility of the method

Area distribution of two-dimensional random walks on a square lattice

The algebraic area probability distribution of closed planar random walks of length N on a square lattice is considered. The generating function for the distribution satisfies a recurrence relation in which the combinatorics is encoded. A particular case generalizes the q-binomial theorem to the case of three addends. The distribution fits the L\'evy probability distribution for Brownian curves with its first-order 1/N correction quite well, even for N rather small.Comment: 8 pages, LaTeX 2e. Reformulated in terms of q-commutator

One-step sculpting of silicon microstructures from pillars to needles for water and oil repelling surfaces

Surfaces that repel both water and oil effectively (contact angles > 150°) are rare. Here we detail the microfabrication method of silicon surfaces with such properties. The method is based on careful tuning of the process conditions in a reactive etching protocol. We investigate the influence of SF6, O2 and CHF3 gases during the etching process using the same pitch of a photolithographic mask. Varying the loading conditions during etching, we optimized the conditions to fabricate homogeneous pedestal-like structures. The roughness of the microstructures could also effectively be controlled by tuning the dry plasma etching conditions. The wetting behavior of the resulting microstructures was evaluated in terms of the water and oil contact angles. Excitingly, the surfaces can be engineered from superhydrophobic to omniphobic by variation of the aforementioned predefined parameter

PHYSIOLOGICAL MONITORING OF FLUID SHIFTS DURING ORTHOSTATIC TILT

BACKGROUND While the etiology of the Spaceflight Associated Neuro-ocular Syndrome (SANS) is currently unknown, headward fluid shifts due to the removal of all gravitational vectors in space is hypothesized to be a major contributing factor. A countermeasure (CM) that can successfully redistribute body fluids similar to the upright position on Earth may thus be important for the prevention of SANS. Our SPACE-CENT Study (Studying the Physiological and Anatomical Effects of Centrifugation and Head-Down Tilt) seeks to investigate the cerebral, ocular and vestibular effects of 60-day exposure to strict 6o head-down tilt bed rest as a spaceflight analog with and without daily centrifugation. METHODS This study is part of the ongoing AGBRESA study at the DLR :envihab facility. As one component of our SPACE-CENT project, near-infrared spectroscopy (NIRS) derived total hemoglobin concentrations ([HbT]) from 4 body locations (head, chest, thigh, and calf) was measured before, during and after the international-standard orthostatic tilt test: tilt from supine to +80o, maintain for 15 min, then increase lower-body negative pressure (LBNP) by +10 mmHg every 3 minutes until subjects exhibit pre-syncope signs via a simultaneous drop in blood pressure and heart rate. RESULTS As of October 2019, the entire protocol has been completed on n=12 subjects (4 females), 5 days before bed rest onset and on R+0 following 60 days of -6o HDT bed rest. Significant shifts in [HbT]—proportional to blood volume—were observed from the head towards the feet during tilt to +80o in all subjects (Figure 1). All subjects had tests terminated sooner on R+0 (462±346 sec) than on BDC-5 (1105±464 sec), although the inter-subject variability was large (range=125-1751 sec). Interestingly, a subset of subjects (n=3) exhibited an initial increase in cerebral [HbT] at the onset of +80o, whereas the remainder showed no change or a decrease in cerebral [HbT] following tilt onset, which was predictive of longer orthostatic trials (t=2.46, p=0.022). All subjects exhibited an accelerating decrease in cerebral [HbT] that preceded test termination by 59±54 sec. CONCLUSIONS This represents preliminary findings from the first campaign of the study (12 of a planned 24 subjects). As such, final conclusions are not yet possible. However, the consistency of findings across subjects suggests that NIRS-based measures of fluid shifts along the body axis—and particularly out of the head—can predict the onset of pre-syncope by up to nearly a minute. Such data could be combined with the simultaneously acquired European Space Agency measurements of blood pressure to improve predictions of orthostatic tolerance

IDPpi:Protein-protein interaction analyses of human intrinsically disordered proteins

Intrinsically disordered proteins (IDPs) are characterized by the lack of a fixed tertiary structure and are involved in the regulation of key biological processes via binding to multiple protein partners. IDPs are malleable, adapting to structurally different partners, and this flexibility stems from features encoded in the primary structure. The assumption that universal sequence information will facilitate coverage of the sparse zones of the human interactome motivated us to explore the possibility of predicting protein-protein interactions (PPIs) that involve IDPs based on sequence characteristics. We developed a method that relies on features of the interacting and non-interacting protein pairs and utilizes machine learning to classify and predict IDP PPIs. Consideration of both sequence determinants specific for conformational organizations and the multiplicity of IDP interactions in the training phase ensured a reliable approach that is superior to current state-of-the-art methods. By applying a strict evaluation procedure, we confirm that our method predicts interactions of the IDP of interest even on the proteome-scale. This service is provided as a web tool to expedite the discovery of new interactions and IDP functions with enhanced efficiency. © 2018 The Author(s)

Quantum Mechanics and Thermodynamics of Particles with Distance Dependent Statistics

The general notion of distance dependent statistics in anyon-like systems is discussed. The two-body problem for such statistics is considered, the general formula for the second virial coefficient is derived and it is shown that in the limiting cases it reproduces the known results for ideal anyons.Comment: 9 pages, LATEX Kiev Institute for Theoretical Physics preprint ITP-93-5E, January 199

Boundary Liouville theory at c=1

The c=1 Liouville theory has received some attention recently as the Euclidean version of an exact rolling tachyon background. In an earlier paper it was shown that the bulk theory can be identified with the interacting c=1 limit of unitary minimal models. Here we extend the analysis of the c=1-limit to the boundary problem. Most importantly, we show that the FZZT branes of Liouville theory give rise to a new 1-parameter family of boundary theories at c=1. These models share many features with the boundary Sine-Gordon theory, in particular they possess an open string spectrum with band-gaps of finite width. We propose explicit formulas for the boundary 2-point function and for the bulk-boundary operator product expansion in the c=1 boundary Liouville model. As a by-product of our analysis we also provide a nice geometric interpretation for ZZ branes and their relation with FZZT branes in the c=1 theory.Comment: 37 pages, 1 figure. Minor error corrected, slight change in result (1.6

Rhyolitic tephra horizons in northwestern Europe and Iceland from the AD 700s-800s: a potential alternative for dating first human impact

The distribution and geochemistry of four rhyolitic tephra horizons from Iceland dated to the ad 700s–800s is assessed. These include the rhyolitic phase of the Landnám tephra (ad 870s), the ad 860 layer, a previously unrecorded tephra called the GA4–85 layer (c. ad 700–800) and the Tjïrnuvík tephra (c. ad 800s). The ad 860 and GA4–85 layers were first found in peat bogs in north Ireland. They are here correlated with equivalent horizons on Iceland which were found below the Landnám tephra (c. ad 870s). This time period is considered important in the North Atlantic region, because it coincides with a phase of human settlement in Iceland and the Faroe Islands. The establishment of a detailed tephrochronology may provide a tool for exact dating of sediment successions and sediments associated with archaeological excavations. Caution must be taken especially on Iceland where the Landnám tephra is often used for dating archaeological sites. This investigation show that several rhyolitic tephra horizons occur close in time to the Landnám tephra, and that mistakes can be made if detailed geochemical analyses are not carried out, especially in areas which are distal to the source of the Landnám tephra (the Veidivötn and Torfajökull volcanic systems, southern Iceland)