Reverse Connection Research Articles

A rapid, reliable, and automatable lab-on-a-chip interface

We present a prototype for a universal world-to-chip interface for electrical and fluidic connections to lab-on-a-chip devices. The concept is based on spring supported connections to secure and define the contact force for each wire and tubing. We demonstrate the functionality of a manual system and propose the design of an automated system. The new interface provides several useful characteristics: A reliable and reversible leak-free connection is rapidly achieved. The fluidic interface sealed a PMMA chip up to a maximal pressure of 2,070 kPa and reliably connected a six port glass chip. Damage during chip assembly is prevented by an easy handling procedure in combination with adjustable and reproducible contact forces. Destructive fluid overpressure during chip operation is avoided by the relief valve functionality of the interface. The compression based setup is easily adaptable to other chip designs. It is biocompatible and can be used for analytical measurements due to the exclusive use of certified materials and its adhesive free design. The new interface overcomes one of the main obstacles in miniaturization, the connection of the lab-on-a-chip device with the macro world.

Does cohesin regulate developmental gene expression in Drosophila ?

Cohesin is a conserved protein complex with a well documented role in providing stable but reversible connections between sister chromatids during both mitosis and meiosis. Cohesin consists of two long coiled-coil proteins (SMC1 and SMC3) and two non-SMC subunits (SCC1/Rad21 and SCC3/SA) that combine to form a ring-like structure. Establishment, maintenance, and timely removal of cohesin-mediated cohesion is critical to ensure regular chromosome segregation (1–3). However, recent findings indicate that in higher eukaryotes chromosome segregation may not be the only major function of cohesin. Several studies have shown an effect of reduction in dose or expression of genes encoding cohesin subunits and of the cohesin loading factor Nipped-B/SCC2 on expression of the cut locus in Drosophila (4–6). Two articles published earlier this year demonstrated that cohesin mutations in Drosophila disrupt axon pruning at a postmitotic stage in development of the Drosophila nervous system by inhibiting expression of the Ecdysone-Receptor (EcR) gene (7, 8). In this issue of PNAS, Hallson et al. (9) suggest a considerably broader role of cohesin in gene regulation in Drosophila. Their findings indicate that mutations in the gene encoding the Rad21 cohesin subunit interact with mutations in hedgehog (hh), a signal-transduction gene with multiple developmental roles (10), and in Polycomb (Pc), which encodes a component of a chromatin complex responsible for silencing expression of multiple homeotic genes during development. These phenotypes are characteristic of mutations in trithorax-group (trxG) genes, which encode a diverse group of chromatin proteins required to counteract Polycomb group (PcG)-mediated silencing and maintain appropriate expression of several genes important for proper identity of Drosophila segments and other developmental processes (11–13). Thus, the findings of Hallson et al. (9) suggest that cohesin may play a fundamental role in developmental gene regulation in addition to its established role in chromosome segregation.

The reverse connectivity pattern between Broca's area and the left visual word form area in the processing of Chinese words and English characters

The reverse connectivity pattern between Broca's area and the left visual word form area in the processing of Chinese words and English characters

The Design of the Drive Control Chip for the Solar LED Lighting System

Combining with the application characteristic of solar energy system and the drive characteristic of high-power lighting LED, in this article, we develop a sort of new drive control chip of solar LED lighting system, which not only can be drove by the invariable current of 350mA, but also can realize functions including the regulation of charger and discharge, preventing reverse charge, preventing over charge, preventing over discharge, and preventing reverse connection of the storage battery in the photovoltaic system.

Experimental study of structural fire behaviour of steel beam to concrete filled tubular column assemblies with different types of joints

This paper presents experimental results of structural fire behaviour of steel beam to concrete filled tubular (CFT) column assemblies using different types of joints. The joint types include fin plate, end plate, reverse channel and T-stub. The structural assembly was in the form of a “rugby goalpost”. In each test, loads were applied to the beam and then the structural assembly was exposed to the standard fire condition in a furnace while maintaining the applied loads. In total, 10 tests were carried out. In eight of the 10 tests, fire exposure continued until termination of the fire test, which was mainly caused by structural failure in the joints under tension when the beam was clearly in substantial catenary action. In the other two tests (one using fin plates and one using reverse channels), fire exposure stopped and forced cooling started when the beam was near a state of pure bending and just about to enter into catenary action. The results of the experiments indicate that even the relatively simple joints used in this study were able to allow the beams to develop substantial catenary action so that the final failure times and beam temperatures of the assemblies were much higher than those obtained by assuming the beams in pure bending. At termination of the tests, the beams reached very high deflections (about span/5), even then failure of the assemblies always occurred in the joints. Therefore, to enable the beams to reach their full potential in catenary action, the joints should be made to be much stronger. The results also indicate that reverse channel connection has the potential to be developed into a robust connection characterised by high stiffness, strength, rotational capacity and ductility. The beams in the two cooling tests developed high tension forces, however there was no structural failure in the assemblies. The principal aim of this paper is to present experimental results of joint behaviour in fire (which until now is lacking) to enable development of better understanding and rational design methods for robust construction of joints to resist extreme fire attack.

Coupler talk - take 2 [Microwave Bytes

In this paper, it is necessary to invert the phase of one of the signals to obtain the desired 100% power addition in the output coupler. Only in the equal power split case ( i.e., 3-dB couplers) can the same effect be obtained more conveniently by the reverse connection of the two equal power outputs; this property is, of course, widely used to make balanced amplifiers

Bulgarian Turks in the context of neighborhood with other ethnic-religious communities in Bulgaria

The special attention that this article devotes to Bulgarian Muslim Turks is due to at least three important issues: first, this is the second largest ethnic and religious group in the country after the Bulgarian Christian majority, and the problems of this community involve a large portion of the population; second, geopolitical circumstances make this group a significant factor for Bulgaria; third, the Islamic religion is of growing political importance in the world: all of these determine some of the emphasis in the following discussion. We have focused specially on the characteristics and regularities of the neighborhood of the Muslim community with the majority; the reverse connection is examined as a correlative; comparisons with other religious communities have been made only if necessary for specific comparisons.

Gelation-driven component selection in the generation of constitutional dynamic hydrogels based on guanine-quartet formation

The guanosine hydrazide 1 yields a stable supramolecular hydrogel based on the formation of a guanine quartet (G-quartet) in presence of metal cations. The effect of various parameters (concentration, nature of metal ion, and temperature) on the properties of this gel has been studied. Proton NMR spectroscopy is shown to allow a molecular characterization of the gelation process. Hydrazide 1 and its assemblies can be reversibly decorated by acylhydrazone formation with various aldehydes, resulting in formation of highly viscous dynamic hydrogels. When a mixture of aldehydes is used, the dynamic system selects the aldehyde that leads to the most stable gel. Mixing hydrazides 1, 9 and aldehydes 6, 8 in 1:1:1:1 ratio generated a constitutional dynamic library containing the four acylhydrazone derivatives A, B, C, and D. The library constitution displayed preferential formation of the acylhydrazone B that yields the strongest gel. Thus, gelation redirects the acylhydrazone distribution in the dynamic library as guanosine hydrazide 1 scavenges preferentially aldehyde 8, under the pressure of gelation because of the collective interactions in the assemblies of G-quartets B, despite the strong preference of the competing hydrazide 9 for 8. Gel formation and component selection are thermoreversible. The process amounts to gelation-driven self-organization with component selection and amplification in constitutional dynamic hydrogels based on G-quartet formation and reversible covalent connections. The observed self-organization and component selection occur by means of a multilevel self-assembly involving three dynamic processes, two of supramolecular and one of reversible covalent nature. They extend constitutional dynamic chemistry to phase-organization and phase-transition events.

Characterizing uncommon Burkholderia cepacia complex isolates from an outbreak in a haemodialysis unit.

An outbreak of bacteraemia in a haemodialysis unit where 65 episodes of infection involved 35 outpatients is reported. Burkholderia cepacia complex was the agent most frequently recovered from blood. Thirty-three environmental and clinical isolates of B. cepacia complex were characterized by whole-cell protein electrophoresis and recA-RFLP profile. Fourteen isolates were genomovar I and 16 isolates were not classifiable by their recA-RFLP pattern. Ribotyping, random amplification of polymorphic DNA (RAPD) and integron profile were used to explore the clonality of the isolates, and revealed multiple strain genotypes. Four ribotypes and RAPD types and three integron patterns were identified. The water supply was identified as the source of the outbreak, and inappropriate cleaning and a leak in the reverse osmosis tubing connection were the probable causes of contamination. B. cepacia complex was still recovered from blood of patients even after apparently adequate measures were taken and water quality standards were met, suggesting that higher standards for water quality should be adopted in haemodialysis units. The genomovars recovered here were distinct from those commonly reported for cystic fibrosis isolates.

Removable tubing interconnects for glass-based micro-fluidic systems made using ECDM

Reversible tubing connections for glass micro-fluidic systems are realized using electro-chemical discharge machining of three-dimensional glass vias. The connections reversibly connect standard sized plastic tubing to holes in borosilicate microscope slides. Tubing connections are demonstrated on a sealed, micro-fluidic channel which is fabricated between two glass slides using SU-8. The connections are experimentally tested to withstand up to 30 psi (~206 kPa) of air pressure without leaking.

A prototype two-dimensional capillary electrophoresis system fabricated in poly(dimethylsiloxane).

A method for carrying out 2D gel electrophoresis in a capillary format is presented. In this method, separation in the first dimension is carried out in a 1D capillary, with this system physically isolated from the capillaries that provide the separation in the second dimension. After completion of the first separation, the 1D channel is physically connected to the 2D capillaries, and a second separation is carried out in an orthogonal set of parallel capillaries. The ability of poly(dimethylsiloxane) (PDMS) to support the fabrication of 3D microfluidic systems makes it possible to produce membranes that both enclose the gel used in the first separation in a capillary and provide passages for the proteins to migrate into the array of orthogonal capillaries. The elastomeric nature of PDMS makes it possible to make reversible connections between pieces of PDMS. The feasibility of this system is demonstrated using a protein mixture containing fluorescein-conjugated carbonic anhydrase, fluorescein-conjugated BSA, and Texas Red-conjugated ovalbumin. This work suggests one type of design that might form the basis for a microfabricated device for 2D capillary electrophoresis.

Flow reversal through the anaesthetic machine back bar: an unusual assembly fault

A new SIMS PneuPac 550 anaesthetic machine (Luton, UK) and Datex AS/3 (Instrumentation Corp, Finland) anaesthetic monitor were commissioned for use in the back-up operating theatre in our maternity unit. This theatre is mostly used for short procedures, e.g. surgical evacuation of the retained products of conception and suturing of vaginal tears, but is occasionally used for␣Caesarean sections when the main obstetric operating theatre is in use. Shortly after the installation of this equipment, it was noticed that the␣monitored concentration of volatile anaesthetic agent delivered to the patient, via a parallel Lack circuit, exceeded that dialled on the vaporiser. The␣problem appeared to resolve after the␣monitor was recalibrated, but appeared to recur a few days later. Over the␣following weeks, the monitor was calibrated again, the vaporiser changed, the monitor serviced and a portable gas analysis␣system used. It was noted that an increase in fresh gas flow resulted in an increase in agent concentration after a short time and it eventually became apparent that the problem lay within the anaesthetic machine. Prior to this realisation, 100 general anaesthetics had been administered using the machine. Fortunately, intravenous maintenance of anaesthesia was used in the vast majority of cases, contributing to the delay in identifying the source of the problem. It was discovered that the back bar of␣the anaesthetic machine had been incorrectly connected, with the input pipe from the flow meters attached to the back bar outlet connection and the back bar inlet pipe attached to the fresh gas outlet pipe. This effectively reversed the flow through the back bar and any attached vaporiser. This fault was the result of an assembly error, as the design of the anaesthetic machine is such that both the inlet and outlet connectors are on the same side of the machine and were unlabelled elbow connectors. The design has since been modified, such that the inlet pipe is attached directly to the back bar and the outlet pipe is attached via a straight connector. The two pipes are of different diameters (10 mm and 8 mm outer diameters) and the screw threads are also different between the two connections (Fig. 5). This should make the potential for reverse connections impossible. In␣addition, the test block, simulating the␣attachment of a vaporiser during assembly and service checks, has been modified to include a one-way valve, blocking gas flow through the test block should reverse flow occur. These modifications have satisfied PneuPac quality control and the Medical Devices Agency that such an error is unlikely to occur again. Inlet and output connectors of the pneuPAC 550 anaesthetic back bar after modifications to prevent future episodes of reverse connection. Reproduced with kind permission of pneuPAC. Twenty-six anaesthetic machines of this specific design had been produced and all were examined for this fault, which was found to be an isolated incident. Reverse flow through a vaporiser may occur with either misconnection of freestanding vaporisers [1, 2] or misconnection during servicing [3]. The delivered agent concentration has been reported as either being unaffected [2] or doubling [1, 3] following a reversal of flow. Our experience with an Ohmeda Tec 4 (West Yorkshire, UK) isoflurane vaporiser is intermediate, as we saw expected delivered concentrations initially, followed by a drift to approximately double the dialled␣concentration. This could potentially lead to problems␣if the volatile anaesthetic concentrations are not monitored in situations where high inspired concentrations are undesirable, e.g. elderly, cardiac disease, obstetrics. This incident highlights the importance of vigilance by anaesthetic personnel in the use of all equipment, especially new equipment and that which has been recently serviced. As we use multiple pieces of increasingly sophisticated equipment, the potential for faults increases, yet it may be difficult to ascertain where the fault lies. The standard anaesthetic equipment check, as published by the Association of Anaesthetists [4], remains essential, but it may not detect assembly faults such as this. Is it time for the development of specific guidelines for the checking of equipment prior to initial commissioning and after each routine service? The assembly fault described may have been detected earlier by the use of vaporisers with non-return valves and has been prevented from recurring by the introduction of changes in the design of the back bar connections, combined with improvements in test equipment and test procedures. This emphasises the importance of simple measures in the overall safety of anaesthesia.

Generalized radial basis function networks for classification and novelty detection: self-organization of optimal Bayesian decision

By adding reverse connections from the output layer to the central layer it is shown how a generalized radial basis functions (GRBF) network can self-organize to form a Bayesian classifier, which is also capable of novelty detection. For this purpose, three stochastic sequential learning rules are introduced from biological considerations which pertain to the centers, the shapes, and the widths of the receptive fields of the neurons and allow a joint optimization of all network parameters. The rules are shown to generate maximum-likelihood estimates of the class-conditional probability density functions of labeled data in terms of multivariate normal mixtures. Upon combination with a hierarchy of deterministic annealing procedures, which implement a multiple-scale approach, the learning process can avoid the convergence problems hampering conventional expectation-maximization algorithms. Using an example from the field of speech recognition, the stages of the learning process and the capabilities of the self-organizing GRBF classifier are illustrated.

Reversible merger of membranes at the early stage of influenza hemagglutinin-mediated fusion.

Fusion mediated by influenza hemagglutinin (HA), a prototype fusion protein, is commonly detected as lipid and content mixing between fusing cells. Decreasing the surface density of fusion-competent HA inhibited these advanced fusion phenotypes and allowed us to identify an early stage of fusion at physiological temperature. Although lipid flow between membranes was restricted, the contacting membrane monolayers were apparently transiently connected, as detected by the transformation of this fusion intermediate into complete fusion after treatments known to destabilize hemifusion diaphragms. These reversible connections disappeared within 10-20 min after application of low pH, indicating that after the energy released by HA refolding dissipated, the final low pH conformation of HA did not support membrane merger. Although the dynamic character and the lack of lipid mixing at 37 degrees C distinguish the newly identified fusion intermediate from the intermediate arrested at 4 degrees C described previously, both intermediates apparently belong to the same family of restricted hemifusion (RH) structures. Because the formation of transient RH structures at physiological temperatures was as fast as fusion pore opening and required less HA, we hypothesize that fusion starts with the formation of multiple RH sites, only a few of which then evolve to become expanding fusion pores.

Dynamic Combinatorial Chemistry and Virtual Combinatorial Libraries

The reversible connection between sets of basic components allows the generation of a large collection of compounds constituted by all possible combinations that are potentially available. It makes virtual combinatorial libraries of substances accessible through a dynamic approach to combinatorial chemistry. The thermodynamically-driven evolution of the system leads to the actual expression of the constituent(s) that present(s) the best binding to/molecular recognition with the target site (see diagram). The general concept of this methodology has wide applications in a variety of areas of science and technology.

Non-persistence of Homoclinic Connections for Perturbed Integrable Reversible Systems

The dynamics of an analytic reversible vector field \(V\)(X,μ) is studied in \(\mathbb{R}^4 \) with one real parameter μ close to 0; X=0 is a fixed point. The differential Dx\(V\)(0,0) generates an “oscillatory” dynamics with a frequency of order 1—due to two simple, opposite eigenvalues lying on the imaginary axis—and it also generates a “slow” dynamics which changes from a hyperbolic type—eigenvalues are \( \pm \sqrt { - \mu } \)—to an elliptic type—eigenvalues are \( \pm {\text{ }}i{\text{ }}\sqrt \mu \)—as μ passes trough 0. The existence of reversible homoclinic connections to periodic orbits is known for such vector fields. In this paper we study a particular subclass of such vector fields, obtained by small reversible perturbations of the normal form. We give an explicit condition on the perturbation, generically satisfied, which prevents the existence of a homoclinic connections to 0 for the perturbed system. The normal form system of any order admits a reversible homoclinic connection to 0, which then does not survive under perturbation of higher order. It will be seen that normal form essentially decouples the hyperbolic and elliptic part of the linearization to any chosen algebraic order. However, this decoupling does not persist arbitrary reversible perturbation, which finally causes the appearance of small amplitude oscillations.

Rehabilitation system in neurologic motor deficiency with using of curative potential of kinesiotherapy

It was developed an optimal and pathogenetically proved system of rehabilitation in neurologic motor deficiency (NMD) in 124 patients with different forms of NMD (results of acute brain circulation disorders, trauma of brain and spinal cord, cerebral paralysis). 35 patients of the control group with the analogous motor pathology were treated by traditionally used method of neurorehabilitation. In the therapeutic programme basic principles of active kinesiotherapy according to H.Kabat and B.Bobath with increasing of their curative effect through stimuli (biologic reverse connection, transcranial magnetic stimulation, conductive therapy). Usage of the offered system of neurorehabilitation resulted in significant improvement of lost motor functions in 29% of cases, in the control group in 14%.

Tolerance for antibiotics’ piiag’s lysis and virulence in hospital strains of staphylococcus aureus

The correlative analysis between tolerance for antibiotics phages lysis and manifestation of pathogenicity factors in. 635 strains S. aureus is performed. The reliable reverse connection between poliresistance to antibiotics of staphylococcus aureus and phages lysis is established. The intimate direct correlation between poll- resistance to antibiotics and the evidence of microbe pathogenicity as hemolytic fibrinolytic activity and chromogenesis is revealed.

Spatial reciprocity of connections between areas 17 and 18 in the cat.

We examined whether the interconnections between areas 17 and 18 are spatially reciprocal, i.e., whether a column of cells in area 17 receives from the same region of area 18 as it sends projections to, and vice versa. We addressed this question by making side by side injections of retrograde fluorescent tracers in area 18, calculating the convergence and divergence of the connections from area 17 to 18. We compared these values with previously reported values of divergence and convergence of the projections from area 18 to area 17. The results demonstrate that there is a good match between the convergence and divergence of the area 17 to area 18 connection and, respectively, the divergence and convergence of the reverse connection. We confirmed directly the spatial reciprocity by injecting simultaneously in area 17 a retrograde and an anterograde tracer and by analyzing quantitatively the density of anterograde and retrograde labeling across the surface of area 18. There was an excellent match between the density maps of retrogradely labeled cells and anterogradely labeled axon terminals in area 18. Connections between areas 17 and 18 therefore exhibit large degrees of convergence and divergence and are spatially reciprocal. Thus, a given column of cells within one of these two areas is reciprocally interconnected with a large region of the opposite area. Such an organization may provide the basis for synchronization of firing of neurons across these two areas, as revealed by cross-correlation studies.

Product dependence of deuterium isotope effects in enzyme-catalyzed reactions.

Theory for enzyme-catalyzed reactions is developed for the dependence on product concentration of deuterium isotope effects on V and V/K. Generally, a product that decreases the off-rate for a second product to zero causes the isotope effect on V/K to decrease to DKeq and that on V to decrease to a value between 1 and DKeq. If the second product off-rate is decreased to a finite value, DV and D(V/K) will decrease to a value greater than DKeq, while if there is no effect on the off-rate for the second product, DV and D(V/K) will not change. Interestingly, for a ping-pong mechanism, the presence of the product that provides a reversible connection between the isotope-sensitive step and the isotope-insensitive half-reaction will give an isotope effect on V/K for the latter. (In the absence of the product, the isotope effect on V/K for the isotope-insensitive half-reaction will be unity.) Theory is supported with data for alcohol and lactate dehydrogenases. For lactate dehydrogenase, D(V/Kpyruvate) decreases from 1.93 +/- 0.02 at zero to 1.16 +/- 0.02 at infinite lactate concentration, while DV decreases from a value of 1.75 +/- 0.03 at zero to a value of 0.93 +/- 0.05 at infinite lactate concentration. Thus, it appears that the pathway in which lactate is released first is greatly preferred, but the pathway in which NAD+ is released before lactate is observed at high lactate concentration.(ABSTRACT TRUNCATED AT 250 WORDS)