Open Gap Research Articles

Mercury Azides and the Azide of Millon’s Base

Always look on the bright azide of life: The synthesis of Millon's base azido salt [Hg2N]N3, and the metastable β-Hg(N3)2, along with their full characterization is possible for the first time and closes an open gap in azide chemistry.

Palm top plasma focus device as a portable pulsed neutron source

Development of a palm top plasma focus device generating (5.2 ± 0.8) × 10(4) neutrons∕pulse into 4π steradians with a pulse width of 15 ± 3 ns is reported for the first time. The weight of the system is less than 1.5 kg. The system comprises a compact capacitor bank, a triggered open air spark gap switch, and a sealed type miniature plasma focus tube. The setup is around 14 cm in diameter and 12.5 cm in length. The energy driver for the unit is a capacitor bank of four cylindrical commercially available electrolytic capacitors. Each capacitor is of 2 μF capacity, 4.5 cm in diameter, and 9.8 cm in length. The cost of each capacitor is less than US$ 10. The internal diameter and the effective length of the plasma focus unit are 2.9 cm and 5 cm, respectively. A DC to DC converter power supply powered by two rechargeable batteries charges the capacitor bank to the desired voltage and also provides a trigger pulse of -15 kV to the spark gap. The maximum energy of operation of the device is 100 J (8 μF, 5 kV, 59 kA) with deuterium gas filling pressure of 3 mbar. The neutrons have also been produced at energy as low as 36 J (3 kV) of operation. The neutron diagnostics are carried out with a bank of (3)He detectors and with a plastic scintillator detector. The device is portable, reusable, and can be operated for multiple shots with a single gas filling.

Creepage discharge on pressboards in synthetic and natural ester transformer liquids under ac stress

This study reports experimental studies of creepage discharges on the pressboard (PB) surface in esters under ac divergent electric field. With the help of commercial partial discharges detector, wideband current measurement and high-speed image recorder, the differences of discharge patterns between open gap and on PB surface were studied in esters as well as in mineral oil. The results show that the presence of PB surface tends to promote discharges, especially negative discharges, and enables more discharges to occur at smaller phase angles. It is believed that the promotion effect of PB surface on discharges is caused by surface charges and bubble residences; because of more intense discharges and higher viscosity of esters, this effect is more significant in esters than in mineral oil.

Circularly Polarized Loop Tag Antenna for Long Reading Range RFID Applications

A novel circularly polarized (CP) loop antenna design for a UHF band (902-928 MHz) radio frequency identification (RFID) tag is proposed to overcome the polarization mismatch problem between reader antenna and tag antenna. The structure of the proposed tag antenna is a simple square-loop type loaded with an open gap, two feeding strips, and a matching stub. The open gap and two feeding strips were used to achieve good CP radiation. Desirable impedance matching between the tag antenna and RFID chip was attained by tuning the matching stub. Besides achieving satisfactory 3-dB axial-ratio and 10-dB impedance bandwidths of approximately 5.5%, good antenna gain and reading range of more than 2.8 dBic and 16.3 m, respectively, were also demonstrated.

Improvement of effectiveness of existing Casuarina equisetifolia forests in mitigating tsunami damage

Coastal vegetation can play a significant role in reducing the severity of a tsunami because the energy associated with the tsunami is dissipated when it passes through coastal vegetation. Field surveys were conducted on the eastern coastline of Sri Lanka to investigate which vegetation species are effective against a tsunami and to evaluate the effectiveness of existing Casuarina equisetifolia forests in tsunami mitigation. Open gaps in C. equisetifolia forests were identified as a disadvantage, and introduction of a new vegetation belt in front or back of the existing C. equisetifolia forest is proposed to reduce the disadvantages of the open gap. Among the many plant species encountered during the field survey, ten species were selected as effective for tsunami disaster mitigation. The selection of appropriate vegetation for the front or back vegetation layer was based on the vegetation thickness per unit area (dNu) and breaking moment of each species. A numerical model based on two-dimensional nonlinear long-wave equations was applied to explain the present situation of open gaps in C. equisetifolia forests, and to evaluate the effectiveness of combined vegetation systems. The results of the numerical simulation for existing conditions of C. equisetifolia forests revealed that the tsunami force ratio (R = tsunami force with vegetation/tsunami force without vegetation) was 1.4 at the gap exit. The species selected for the front and back vegetation layers were Pandanus odoratissimus and Manilkara hexandra, respectively. A numerical simulation of the modified system revealed that R was reduced to 0.7 in the combined P. odoratissimus and C. equisetifolia system. However, the combination of C. equisetifolia and M. hexandra did not effectively reduce R at the gap exit. Therefore, P. odoratissimus as the front vegetation layer is proposed to reduce the disadvantages of the open gaps in existing C. equisetifolia forests. The optimal width of P. odoratissimus (W1) calculated from the numerical simulation was W1 = 10 m. R at the exit of a 15-m-wide open gap was 0.8, and therefore the proposed system was appropriate for cases with the highest velocity at the gap exit as well. Establishment of a new front vegetation layer except for open gaps that are essential, such as access roads to the beach, is proposed.

Prognostic Value of TP53 Gene Mutations in Higher Risk MDS Treated with Azacitidine

AbstractAbstract 1706▪▪This icon denotes a clinically relevant abstract Background:TP53 gene mutations in MDS and AML are, with the exception of cases of isolated del 5q, generally associated with complex karyotype, often including del (17p) (with loss of the remaining TP53 allele) and with poor overall outcome (Fenaux, BJH, 1992; Bejar, NEJM, 2011). They are, in MDS and AML, more specifically generally associated with resistance to chemotherapy, including anthracycline-Ara C combinations and low-dose AraC (Wattel, Blood, 1994), but their correlation with treatment outcome with hypomethylating agents has not been studied. Our aim was to assess the prognostic value of TP53 mutations for response to Azacitidine (AZA) in higher risk MDS, AML with 20–30% blasts or advanced CMML (corresponding to the EU label for AZA). Methods:Patients were treated with AZA (75 mg/m2/d, generally during 7 days every 4 weeks) in 2 centers of the Groupe Francophone des Myélodysplasies. TP53 mutations were detected by the functional FASAY technique, which assesses the transcriptional activity of p53 by co-transfecting an open gap repair plasmid with the product of amplification of TP53 from patients in yeasts whose growth is dependent on the functionality of p53. The detection limit of this technique is around 10–15% (Flaman et al, PNAS 1995). The presence of mutations was subsequently confirmed by direct sequencing using the Sanger method and, more recently, by a Next-Generation Sequencing (NGS) assay using pyrosequencing (GS Junior System, Roche with the IRON II plate design). Results:72 pts treated with AZA (median n° of cycles of AZA received 4, range 1–7) were analyzed, including 34 MDS according to WHO classification (IPSS high: 9, int2: 13, int1: 6, undetermined: 6), 33 AML with 20–30% blasts and 5 advanced CMML. According to IPSS, karyotype was favorable in 27%, intermediate in 13% and unfavorable in 60% of the pts, including 47% of complex karyotypes.Response to AZA (according to IWG 2006 criteria) was observed overall in 51% of the pts, including 34% CR, 6% PR, 4% marrow CR, 7% stable disease with HI. Median overall survival (OS) from onset of AZA was 15.6 months, possibly explained by the 47% of complex karyotypes.29 (40%) patients had a TP53 mutation, detected by FASAY technique and subsequently confirmed by Sanger sequencing or NGS (no false positive with FASAY technique was observed). 22 of the 34 (67%) patients with complex karyotype had a TP53 mutation. In the 7 patients with TP53 mutation without complex karyotype, 3 pts had isolated del(5q), 2 had del (17p) (isolated in 1 pt, with del (20q) in 1 pt), 1 had pentasomy 11 and 1 had +8, del(20q). Ten (77%) of the 13 cases with chromosome 17 rearrangement leading to del (17p) were TP53 mutated.Overall Response to AZA (41% vs 57%, p= 0.227) and CR rate (21% vs 42%, p= 0.073) did not significantly differ between TP53 mutated and wild-type patients. Nevertheless, OS was negatively influenced by the presence of TP53 mutation (median 13 vs 21 months, p= 0.0022, figure 1), complex cytogenetics (median 14 vs 18 months, p=0.0120), WHO AML diagnosis (median 13 vs 21 months for WHO-MDS or CMML, p= 0.0014). By multivariate analysis, marrow blast % (HR 1.03 (1.01–1.05) (p<10-4)) and TP53 mutational status (HR 2.29 (1.06–4.97) p=0.035) were the only 2 factors retaining statistical significance for OS. When the analysis was restricted to WHO MDS and CMML patients, only the presence of TP53 mutation was associated with worse OS in multivariate analysis (HR=4.08 (1.31– 12.7), p=0.015)). Conclusion:In higher risk MDS (and AML with 20–30% blasts and advanced CMML) patients treated with AZA, the presence of TP53 mutation appears to constitute an independent prognostic parameter of poorer survival. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Incidence and Prognostic Value of TP53 Mutations in Lower Risk MDS with Del 5q.

AbstractAbstract 2809 Background:TP53 gene mutations, frequent in AML and MDS with complex karyotype, have recently been found in about 20% of lower risk MDS with del 5q, where they possibly conferred resistance to lenalidomide (LEN), and a higher risk of AML progression (Jadersten, JCO, 2011). We assessed the incidence and prognostic value of TP53 mutations in 79 lower risk MDS with del 5q, treated or not with LEN, and analysed in early disease phase or after progression to higher risk MDS or AML. Methods:IPSS low and int 1 (Lower) risk MDS with del 5q were analysed at diagnosis or onset of LEN (“early phase”) and/or after progression to IPSS high or int 2 (higher) risk MDS or AML. LEN was administered at 5 or 10 mg/d during 16 weeks, and continued in erythroid responders until relapse or disease progression.TP53 mutations were detected by the functional FASAY technique, assessing the transcriptional activity of p53 by co-transfecting an open gap repair plasmid with the product of amplification of TP53 from patients in yeasts whose growth is dependent on p53 functionality. The detection limit of this technique is around 10–15% (Flaman, PNAS 1995). Mutations found by FASAY were confirmed by direct sequencing, using Sanger method and /or (more recently) high sensitivity (1%) Next Generation Sequencing (NGS) by pyrosequencing (GS Junior System-Roche, with the IRON II plate design). Results:79 lower risk MDS with del 5q from 6 French centers of the GFM were analyzed, including 62 at diagnosis or onset of LEN (“early phase”), and 17 after progression to higher risk MDS or AML (5 of the latter were also retrospectively analysed on early phase samples).Overall, 28 (35%) of the 79 patients had TP53 mutation, including 16 (26%) of the 62 pts analyzed at early phase and 12 (70%) of the 17 evaluated after higher risk MDS or AML progression (p= 0.001).The 62 early phase pts had marrow blasts <5% and 5–9% in 91 and 9% of the cases, isolated del 5q, del 5q+1 and del5q+>1 (complex karyotype) in 84, 14 and 2% of the cases, and IPSS low and int 1 in 80 and 20% of the cases, respectively. No significant difference was found between mutated and non mutated cases for baseline characteristics including gender, age, WHO classification, cytogenetic complexity and IPSS. In the 5 pts analysed after progression where early phase samples were available, who all had received LEN, 4 had TP53 mutation at progression. In all of them, TP53 mutation was already detectable during early phase. However, the percentage of mutated colonies found by FASAY increased with progression, from 18 to 75%, 26 to 55%, 12 to 87% and 13 to 23%, respectively, showing an increase of the size of the mutated clone at progression.Among the 43 pts analyzed in early phase who received LEN (we excluded the 5 pts analysed after progression where early phase samples were available, to avoid bias), 36 (84 %) had isolated del 5q, 6 (14%) del 5q+1, and 1 (2%) had complex karyotype. IPSS was low in 73% and int-1 in 27%. 12/43 (28%) had TP53 mutation. 63% of the 43 pts achieved erythroid response, and 9 (47%) of the 19 pts evaluable at erythroid response achieved cytogenetic response. Erythroid response was seen in 45% mutated vs 71% non mutated cases (p= 0.258). Cytogenetic response was seen in 1/8(12%) mutated vs 8/11 (73%) non mutated cases (p=0.020). In those 43 pts who received LEN, the cumulative incidence (CI) of AML evolution, with death as a competitive event, did not significantly differ between patients with or without TP53 mutation (3 year CI of 35% vs 30%, p=0.33). Finally, in those pts, TP53 mutational status had no significant impact on OS (median 49 months in mutated pts vs not reached in non mutated pts, p=0.48, figure 1). Conclusion:We confirm the presence of TP53 mutations in about 25 % of lower risk MDS with del 5q analysed in early disease phase. TP53 mutations, in those patients, were not correlated with other baseline parameters. When treated with LEN, mutated cases had similar hematological response, lower cytogenetic response but no significant difference in progression to higher risk MDS or AML and survival compared to non mutated cases. The high incidence of TP 53 mutations at progression to higher risk MDS/AML (70%), and the increase in the TP53 mutated clone size observed during progression in pts with a baseline mutation support the pathophysiological importance of TP53 mutations in disease progression in lower risk MDS with del 5q. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Debris and consequences in micro electric discharge machining of micro-holes

The tip shape of a blind micro-hole produced using micro electrical discharge machining varies with respect to the process parameters used during machining. The usual tip shape is a blunt geometry within the common range of applications, however, under specific machining conditions and machining depths, the tip shape changes drastically to an inverted concaved shape. The origin of such tip deformation in micro electric discharge machining of blind micro-holes was investigated. It was observed that debris particles produced during machining accumulated at the tip, formed a hill and functioned as a tool electrode especially when using fine machining conditions. The phenomena is elaborated experimentally with the affecting parameters to describe the wear mechanism. Open gap voltage, pulse energy and tool rotation speed are examined as varying parameters during the experiments.

Plasma isotopic effect on the damping rate of toroidal Alfvén eigenmodes with intermediate toroidal mode numbers**This paper follows up the contribution presented at the 12th IAEA Technical Committee Meeting on Energetic Particles in Magnetic Confinement Systems (Austin, TX, 8–10 September 2011).

This paper reports on the results of recent experiments performed on the JET tokamak on toroidal Alfvén eigenmodes (TAEs) with toroidal mode number (n) in the range up to |n| = 7. The stability properties of these medium-n TAEs are investigated experimentally using a set of compact in-vessel antennas, providing a direct and real-time measurement of the frequency, damping rate and amplitude for each individual toroidal mode number. The measurements, reported here, of the damping rate (γ/ω) for these medium-n modes were obtained during a deuterium to helium to hydrogen changeover experimental campaign, and are used to infer the effect of the plasma effective isotopic composition (AEFF) on the stability properties of these medium-n TAEs. We find that the damping rate of n = 1 TAEs decreases approximately as γ/ω ∼ 1/AEFF as reported previously, but only for modes whose frequency is close to the centre of the n = 1 toroidal gap and for density and current profiles giving an open gap structure. Conversely, for n ⩾ 3 TAEs we find that their damping rate approximately increases as γ/ω ∼ AEFF.

Preparing for the Road Ahead

The practice of orthopaedic trauma has been considered "a young person's game," but there are many before you who have maintained a fulfilling, successful, and long-lasting career in orthopaedic trauma. The keys to longevity are avoiding burnout and developing a supportive team of practice partners, mentors, and other colleagues. It is important to develop and continually refine a series of "5-year plans" to make sure that you are progressing toward your goals. Develop a specialized niche in 1 or 2 areas that fills an open gap in your community and in which you can really flourish. Finally, it is critical to maintain your skills in a trauma-related discipline that can be built into an elective practice that provides referrals, fills the gaps when trauma slows, and is something that you enjoy.

Quantum mechanics on a Möbius ring: Energy levels, symmetry, optical transitions, and level splitting in a magnetic field

We investigate the quantum mechanical energy levels of an electron constrained to motion on a nanoscale M\"obius ring by solving the Schr\"odinger equation on the curved surface. The dimensions of the ring in terms of the lateral and transverse parameters {$u,v$} for the M\"obius ring allow us to identify the quantum numbers for the levels by $({n}_{u},{n}_{v})$. We show that the energy levels can still be labeled using the quantum numbers of the cylindrical ring of the same dimensions. While the Hamiltonian has invariance under parity in parameter space, the rotational symmetry about any axis in configuration space is lost, so that the double degeneracy of energy levels for azimuthal quantum number ${n}_{u}\ensuremath{\ge}1$, that exists in cylindrical rings, is lifted by a small amount in the M\"obius ring. The pattern of level splitting has been identified in terms of the number of twists $\ensuremath{\sigma}$ to be $2{n}_{u}=s\ensuremath{\sigma}$ where $s$ is an integer. The scaling properties of the energy levels with respect to the dimensions of the ring are derived; using these properties, our numerical results which are given for a specific geometry can be extended to rings of other commensurate dimensions. The absence of rotational invariance for the M\"obius ring manifests itself through the orbital angular momentum ${L}_{z}$ not commuting with the Hamiltonian. Its expectation values are found to have nearly integral as well as half-integral values of $\ensuremath{\hbar}$, and its variances are small. The energy levels with half-integral azimuthal quantum numbers (${n}_{u}$) are also close to the approximate formula for the equivalent cylindrical ring, provided such half-integral quantum numbers are allowed for the cylindrical geometry. The Zeeman splitting of the energy levels in an external magnetic field is displayed, together with wave functions at a level anticrossing. The optical transitions between electronic states on the M\"obius ring are obtained, and a table of oscillator strengths is provided. The results for energy levels for rings with multiple twists are presented. In view of recent technological advances in the production of graphene sheets, we may anticipate the making of such twisted rings with graphene strips of finite width. Graphene strips of finite width have an open band gap at the $K$ points in the Brillouin zone, so that a nonrelativistic treatment with a small effective mass is appropriate. For M\"obius rings of graphene, our results would be directly relevant, and we may anticipate their experimental verification in the near future.

Interplay between gap junctions and K2P‐channels: the switch from PDBu‐elicited contraction to the dilation of the thoracic aorta

Phorbol‐12,13‐dibutyrate (PDBu) an activator of protein kinase C (PKC) was shown to mediate contraction in several vascular beds. PDBu (1μM) increased amplitude of the K+‐currents in freshly isolated myocytes from the aorta. The fraction of PDBu‐elicited K+‐currents was inhibited by “cocktail” of K+‐blockers: TEA (3mM), 4AP (3mM), charibdotoxin (200nM), apamin (1μM) and glibenclamide (10μM) (n=27). The amplitude of the “cocktail” blockers resistive whole cell K+‐currents were reduced partially by Zn (40μM), acid pH (6.5), Ba (300μM) and mercury Hg (5μM). Aorta rings mounted on Mulvany myograph were stretched by step pulse of 8 mN. “Cocktail” of K+‐blockers contracted pre‐stretched aorta. PDBu added cumulatively to the bath solution further contracted aorta. Carbenoxolone (200μM) added to the bath solution prior to the PDBu produced partial dilation of the aorta. PDBu added cumulatively to the carbenoxolone dilated all aorta rings. Go 6983 (20μM) nonselective PKC inhibitor antagonized PDBu‐elicited dilation. Low extracellular pH, zinc and mercury partially antagonized PDBu‐elicited dilation. Our data suggest that PKC contracts the aorta and opens K2P channels simultaneously. PKC dilated the aorta when intercellular coupling via gap junctions was inhibited. We propose that ratio between open gap junctions and K2P channels may switch from PKC mediated vasoconstriction to vasodilation.

A simple generator of a stationary flow of non-equilibrium atmospheric-pressure plasma

A simple design of a plasma discharge set up, providing a stationary flow of non-equilibrium atmospheric-pressure plasma is proposed. The non-equilibrium state of plasma is maintained by using a cathode with a weakly conducting liquid like tap water. The anode is formed with a cooled metal ring-shaped inserted in a dielectric barrel. This assembly is fixed at ∼ 1 cm above the water surface. The velocity of the air flow through the anode hole may be changed from 0 m/s up to ∼ 10 m/s. The studied discharge in the open air gap between the tap water surface and the anode ring is powered by direct current I ∼ 0.1 A. The voltage on the air gap is ≥ 1 kV. Measurements of current-voltage characteristics at different flow velocities were carried out. Spectra of radiation of the discharge column and the torch above the anode were measured. The measurement results were compared with the results of radiation spectra modeling for non-equilibrium plasma of humid air. The comparison made possible to determine the characteristics of plasma. The characteristics of the plasma depending on the speed of the airflow and the current are studied.

Cut-loading: A Useful Tool for Examining the Extent of Gap Junction Tracer Coupling Between Retinal Neurons

In addition to chemical synaptic transmission, neurons that are connected by gap junctions can also communicate rapidly via electrical synaptic transmission. Increasing evidence indicates that gap junctions not only permit electrical current flow and synchronous activity between interconnected or coupled cells, but that the strength or effectiveness of electrical communication between coupled cells can be modulated to a great extent1,2. In addition, the large internal diameter (~1.2 nm) of many gap junction channels permits not only electric current flow, but also the diffusion of intracellular signaling molecules and small metabolites between interconnected cells, so that gap junctions may also mediate metabolic and chemical communication. The strength of gap junctional communication between neurons and its modulation by neurotransmitters and other factors can be studied by simultaneously electrically recording from coupled cells and by determining the extent of diffusion of tracer molecules, which are gap junction permeable, but not membrane permeable, following iontophoretic injection into single cells. However, these procedures can be extremely difficult to perform on neurons with small somata in intact neural tissue.Numerous studies on electrical synapses and the modulation of electrical communication have been conducted in the vertebrate retina, since each of the five retinal neuron types is electrically connected by gap junctions3,4. Increasing evidence has shown that the circadian (24-hour) clock in the retina and changes in light stimulation regulate gap junction coupling3-8. For example, recent work has demonstrated that the retinal circadian clock decreases gap junction coupling between rod and cone photoreceptor cells during the day by increasing dopamine D2 receptor activation, and dramatically increases rod-cone coupling at night by reducing D2 receptor activation7,8. However, not only are these studies extremely difficult to perform on neurons with small somata in intact neural retinal tissue, but it can be difficult to adequately control the illumination conditions during the electrophysiological study of single retinal neurons to avoid light-induced changes in gap junction conductance.Here, we present a straightforward method of determining the extent of gap junction tracer coupling between retinal neurons under different illumination conditions and at different times of the day and night. This cut-loading technique is a modification of scrape loading9-12, which is based on dye loading and diffusion through open gap junction channels. Scrape loading works well in cultured cells, but not in thick slices such as intact retinas. The cut-loading technique has been used to study photoreceptor coupling in intact fish and mammalian retinas7, 8,13, and can be used to study coupling between other retinal neurons, as described here.

Cut-loading: A Useful Tool for Examining the Extent of Gap Junction Tracer Coupling Between Retinal Neurons

In addition to chemical synaptic transmission, neurons that are connected by gap junctions can also communicate rapidly via electrical synaptic transmission. Increasing evidence indicates that gap junctions not only permit electrical current flow and synchronous activity between interconnected or coupled cells, but that the strength or effectiveness of electrical communication between coupled cells can be modulated to a great extent1,2. In addition, the large internal diameter (~1.2 nm) of many gap junction channels permits not only electric current flow, but also the diffusion of intracellular signaling molecules and small metabolites between interconnected cells, so that gap junctions may also mediate metabolic and chemical communication. The strength of gap junctional communication between neurons and its modulation by neurotransmitters and other factors can be studied by simultaneously electrically recording from coupled cells and by determining the extent of diffusion of tracer molecules, which are gap junction permeable, but not membrane permeable, following iontophoretic injection into single cells. However, these procedures can be extremely difficult to perform on neurons with small somata in intact neural tissue. Numerous studies on electrical synapses and the modulation of electrical communication have been conducted in the vertebrate retina, since each of the five retinal neuron types is electrically connected by gap junctions3,4. Increasing evidence has shown that the circadian (24-hour) clock in the retina and changes in light stimulation regulate gap junction coupling3-8. For example, recent work has demonstrated that the retinal circadian clock decreases gap junction coupling between rod and cone photoreceptor cells during the day by increasing dopamine D2 receptor activation, and dramatically increases rod-cone coupling at night by reducing D2 receptor activation7,8. However, not only are these studies extremely difficult to perform on neurons with small somata in intact neural retinal tissue, but it can be difficult to adequately control the illumination conditions during the electrophysiological study of single retinal neurons to avoid light-induced changes in gap junction conductance. Here, we present a straightforward method of determining the extent of gap junction tracer coupling between retinal neurons under different illumination conditions and at different times of the day and night. This cut-loading technique is a modification of scrape loading9-12, which is based on dye loading and diffusion through open gap junction channels. Scrape loading works well in cultured cells, but not in thick slices such as intact retinas. The cut-loading technique has been used to study photoreceptor coupling in intact fish and mammalian retinas7, 8,13, and can be used to study coupling between other retinal neurons, as described here.

Discrete spectrum of quantum Hall effect Hamiltonians II: Periodic edge potentials

We consider the unperturbed operator H0 := (−ir − A) 2 + W, self-adjoint in L 2 (R 2 ). Here A is a magnetic potential which generates a constant magnetic field b > 0, and the edge potential W = W is a T -periodic non constant bounded function depending only on the first coordinate x 2 R of (x,y) 2 R 2 . Then the spectrum �(H0) of H0 has a band structure, the band functions are bT -periodic, and generically there are infinitely many open gaps in �(H0). We establish explicit sufficient conditions which guarantee that a given band of �(H0) has a positive length, and all the extremal points of the corresponding band function are non degenerate. Under these assumptions we consider the perturbed operators H� = H0 � V where the electric potential V 2 L 1 (R 2 ) is non-negative and decays at infinity. We investigate the asymptotic distribution of the discrete spectrum of Hin the spectral gaps of H0. We introduce an effective Hamiltonian which governs the main asymptotic term; this Hamiltonian could be interpreted as a 1D Schrodinger operator with infinite-matrix-valued potential. Fur- ther, we restrict our attention on perturbations V of compact support. We find that there are infinitely many discrete eigenvalues in any open gap in the spectrum of �(H0), and the convergence of these eigenvalues to the corresponding spectral edge is asymptotically Gaussian.

Micro free-flow electrophoresis with injection molded chips

In this work we present an approach towards economic free-flow electrophoresis chips fabricated by injection molding as mass replication process. This is achieved by the development of a free-flow electrophoresis chip design suitable for one step molding fabrication. Integrated partitioning bars are incorporated as key elements for bubble segregation. A defined open gap of 20 μm in height and 500 μm in width was integrated between the separation chamber and the electrode channels, acting as a barrier for gas bubbles while maintaining electrical contact by the fluidic junction. Additionally, we present an approach to avoid internal electrodes in FFE microchips for a facile mass production process. The injection molded thermoplastic μFFE chips are ready to use without subsequent labor-intensive implementation of membranes or comparable structures serving as salt bridges.

System design of a small OpenPET prototype with 4-layer DOI detectors

We have proposed an OpenPET geometry which consists of two axially separated detector rings. The open gap is suitable for in-beam PET. We have developed the small prototype of the OpenPET especially for a proof of concept of in-beam imaging. This paper presents an overview of the main features implemented in this prototype. We also evaluated the detector performance. This prototype was designed with 2 detector rings having 8 depth-of-interaction detectors. Each detector consisted of 784 Lu(2x)Gd(2(1-x))SiO₅:Ce (LGSO) which were arranged in a 4-layer design, coupled to a position-sensitive photomultiplier tube (PS-PMT). The size of the LGSO array was smaller than the sensitive area of the PS-PMT, so that we could obtain sufficient LGSO identification. Peripheral LGSOs near the open gap directly detect the gamma rays on the side face in the OpenPET geometry. Output signals of two detectors stacked axially were projected onto one 2-dimensional position histogram for reduction of the scale of a coincidence processor. Front-end circuits were separated from the detector head by 1.2-m coaxial cables for the protection of electronic circuits from radiation damage. The detectors had sufficient crystal identification capability. Cross talk between the combined two detectors could be ignored. The timing and energy resolutions were 3.0 ns and 14%, respectively. The coincidence window was set 20 ns, because the timing histogram showed that not only the main peak, but also two small shifted peaks were caused by the coaxial cable. However, the detector offers the promise of sufficient performance, because random coincidences are at a nearly undetectable level for in-beam PET experiments.

Gap Junction-Mediated Communications Regulate Chromatin Remodeling During Bovine Oocyte Growth and Differentiation Through cAMP-Dependent Mechanism(s)1

Oocyte development is characterized by impressive changes in chromatin structure and function in the germinal vesicle (GV) that are crucial in conferring to the oocyte meiotic and developmental competence. During oogenesis, oocyte and follicular cells communicate by paracrine and junctional mechanisms. In cow, cumulus-enclosed oocytes (CEOs) isolated from early antral follicles have uncondensed chromatin (GV0), functionally open gap junction (GJ)-mediated communications, and limited meiotic competence. The aim of the present study was to analyze the role of GJ communications on the chromatin remodeling process during the specific phase of folliculogenesis that coincides with the transcriptional silencing and the sequential acquisition of meiotic and developmental capability. CEOs were cultured in a follicle-stimulating hormone-based culture system that sustained GJ coupling and promoted oocyte growth and transition from GV0 to higher stages of condensation. When GJ functionality was experimentally interrupted, chromatin rapidly condensed, and RNA synthesis suddenly ceased. These effects were prevented by the addition of cilostamide, a phosphodiesterase 3 inhibitor, indicating that the action of GJ-mediated communication on chromatin structure and function is mediated by cAMP. Prolonging GJ coupling during oocyte culture before in vitro maturation enhanced the ability of early antral oocytes to undergo meiosis and early embryonic development. Altogether, the evidence suggests that GJ-mediated communication between germinal and somatic compartments plays a fundamental role in the regulation of chromatin remodeling and transcription, which in turn are related to competence acquisition.

Effect of applied field and rate of voltage rise on surface breakdown of oil-immersed polymers

In sub-systems of high-voltage, pulsed-power machines, the introduction of a solid into bulk liquid insulation located between two conductors is often necessary to provide mechanical support. Breakdown events on or around the surface of the solid can result in permanent damage to the insulation system. Described in the present paper are experimental results pertaining to surface breakdown of five different solid dielectrics held between plane-parallel electrodes immersed in mineral oil. The effect of varying level of peak applied field from 200 kV/cm (dV/dt 70 kV/μs) to 1 MV/cm (dV/dt 350 kV/μs) is investigated, and the breakdown voltages and times to breakdown are compared to those for an open oil gap. The time to breakdown is shown to be reduced by the introduction of a solid spacer into the gap. Rexolite and Torlon samples suffered significant mechanical damage, and consistently showed lower breakdown voltage than the other materials ¿ average streamer propagation velocity up to 125 km/s was implied by the short times to breakdown. Although ultra-high molecular weight polyethylene yielded the longest times to breakdown of the five types of liquid-solid gap, breakdown events could be initiated at lower levels of applied field for spacers of this material than those with permittivity closely matched to that of the surrounding mineral oil. Polypropylene and low-density polyethylene are concluded to provide the most stable performance in mineral oil. Due to the similarity of the applied voltage wave-shape (1/6.5 μs) to short-tail lightning impulses, the results may also be of interest to high-voltage system designers in the power industry.