Total Number Of Junctions Research Articles

String Junction Model, Cluster Hypothesis, Penta-Quark Baryon and Tetra-Quark Meson

Thirty years ago we proposed string junction model of hadrons and examined structure and reaction of hadrons including exotic ones. Mass m of exotic hadrons of light quarks is roughly given by m ∼ NJ · mB ,w hereNJ is the total number of junctions and mB ∼ 1 GeV is the ordinary light baryon mass. In this paper we introduce “cluster hypothesis” into the model by which mass of a complex hadron is given by the sum of masses of clusters composing it. The hypothesis guarantees the established picture that mass differences of hadrons of the same string junction structure are due to those of the constituent quarks. A candidate for penta-quark baryon Θ (1530 MeV, S = +1) including a strange antiquark s and that for tetra-quark meson Z + (4430 MeV) recently reported by the Belle collaboration are examined in parallel. Θ is considered to have non-strange partners, which are lighter by the mass difference Δs between strange and non-strange quarks. Mass of such light penta-quark baryons with NJ = 3 is expected to be about 3 GeV. Several parameters of the model are estimated such as mass of junction of mJ ∼ O(10) MeV. While mass of light tetra-quark meson with NJ = 2 is expected to be about 2 GeV, Z + (4430 MeV) containing (u, c, d, c) gives a clue to determine some parameters of the model, e.g., inter-junction string energy mIJ.

Stress‐Mediated Hormetic Modulation of Aging, Wound Healing, and Angiogenesis in Human Cells

Aging is amenable to intervention and prevention by mild stress-induced hormesis. Previously, we have reported that repeated mild heat stress has antiaging and other beneficial effects on growth and a range of cellular and biochemical characteristics of normal human skin fibroblasts and keratinocytes undergoing aging in vitro. We have also established a model system of sugar-induced premature senescence in human cells, which can be useful for monitoring the protective and hormetic effects of other treatments. We have now initiated studies on testing the hormetic effects of glyoxal and heat shock on the wound-healing capacity of skin fibroblasts and on the angiogenic ability of endothelial cells. The effects of glyoxal on the extent of wound closure in vitro showed a typical biphasic hormetic curve with 20-40% stimulation at lower doses (up to 0.125 mmol) and more than 50% inhibition at concentrations above 0.5 mmol. In the case of angiogenesis by endothelial cells, measured by the standard tube formation assay on Matrigel, a prior exposure to mild heat shock at 41 degrees C for 1 h increased the total tube length and total number of junctions by 30-60% and 10-14%, respectively. In contrast, a severe heat shock at 42.5 degrees C had slightly inhibitory effects on total tube length and the number of junctions. These data add to the ever-growing body of evidence in support of the view that mild stress-induced hormesis can be a useful approach for the modulation, intervention, and prevention of aging and age-related impairments.

Critical current control and microwave-induced characteristics of (NbN/TiN/sub x/)/sub n//NbN stacked junction arrays

Stacked double and triple Josephson junctions with NbN electrodes and TiN/sub x/ barriers were fabricated for the next-generation 10 V programmable Josephson voltage standard. Because of difficulties in the growth of uniform junctions in a stack with a constant barrier thickness, a stack with carefully engineered thicknesses was grown that exhibited uniform junction properties. The junction arrays on these chips were biased with microwave power at 16 GHz resulting in constant-voltage steps consistent with the total number of junctions in the array, including the multiple junctions in the stacks. The steps had a current range greater than 1 mA at 4.2 K.

Inaccuracy in manual multisegmental irradiation in coronary arteries

Purpose: Retrospective evaluation of the accuracy of manual multisegmental irradiation with a source train for irradiation of long (re)stenotic lesions in coronary arteries, following percutaneous transluminal coronary angioplasty (PTCA). Material and methods: Thirty-six patients were treated with intracoronary irradiation following PTCA with manual multisegmental irradiation. These patients were included in the multicenter, multinational ‘European Surveillance Registry with the Novoste Beta-Cath system’ (RENO). In all 36 patients the target length (i.e. PTCA length plus 5-mm margin at each side) was too long for the available source train lengths (30 and 40 mm). In 33 patients the radiation delivery catheter was manually positioned twice and in three patients three times in series, trying to avoid any gap or overlap. The total number of junctions was 39. Following a successful PTCA procedure the site of angioplasty was irradiated using the Novoste Beta-Cath afterloader with a 5-F non-centered catheter which accommodates the sealed beta-emitting 90Sr/ 90Y source train or dummy source train. Radiation was delivered first to the distal part of the target length. Fluoroscopic images of this source position were stored in the computer memory. For irradiation of the proximal part of the target length, the delivery catheter had to be retracted over a distance equal to the source length used for the distal part. This was done by a continuous overlay video loop with ECG-gated replay of the image stored in the computer memory. The dummy source was used to position the delivery catheter so that the junction between both source positions was as precise as possible. Measurements of gap or overlap between the source positions were performed retrospectively on printed images. Doses were calculated, in accordance with the Novoste study protocol, at a distance of 2 mm from the source axis (=dose prescription distance) in several points along the irradiated length. Results: Interventional or PTCA length varied between 33 and 95 mm. The lesion sites were in the left anterior descending artery, ( n=6), right coronary artery ( n=20), left circumflex artery ( n=6) and one vein graft. The administered radiation dose was determined by the vessel diameter and the presence of a stent. This dose, prescribed at a distance of 2 mm from the source axis, varied between 16 and 22 Gy. No gap or overlap was seen between the two source trains in only two out of 39 cases. In 16 cases there was a gap ranging between 0.6 and 9.6 mm and 18 cases showed an overlap of 0.5–14.4 mm. In three patients the measurement was not possible. In case of a gap the minimal dose calculated at 2 mm from the source axis varies between 0 and 87% of the prescribed dose, depending on the distance between both sources. In case of overlap the maximal dose varies between 110 and 200% of the prescribed dose at 2 mm from the source axis. Conclusions: The results show the inaccuracy of manual multisegmental irradiation using a source train in coronary arteries, causing unacceptable dose inhomogeneities at a distance of 2 mm from the source axis at the junction between both source positions. Moreover, a perfect junction will never be possible due to movement of the non-centered radiation delivery catheter in the vessel lumen, as applied in this study. Manual multisegmental irradiation is therefore not recommended. Using longer line sources or source trains or preferably an automated stepping source is a more reliable and safer technique for treatment of long lesions.

Suitability of gap frequencies for the Josephson voltage standard

We report theoretical investigations of Shapiro step formation at high microwave drive frequencies. A drive frequency equal to the gap frequency or its first subharmonic generates current-voltage characteristics that are especially well suited for Josephson voltage standards. Such drive frequencies increase the stability of the reference voltage and reduce the total number of junctions required to produce a given voltage. In contrast to conventional series-array voltage standards, the dc current bias has to be chosen on the order of the critical current.

Three-dimensional reconstruction of a rat stage V Sertoli cell: III. A study of specific cellular relationships.

Specific Sertoli--Sertoli and Sertoli--germ-cell contacts and/or junctions were investigated employing micrographs used to reconstruct serially a model of a rat stage V Sertoli cell. The Sertoli--Sertoli junctional contact areas occurred in a belt-like arrangement near the base of the Sertoli cell. This configuration is consistent with their proposed function as a sealing element limiting the passage of materials toward the tubular lumen. Sertoli ectoplasmic specializations also formed a continuous belt, or band, around the reconstructed cell at the junctional contact area. Eighteen Sertoli--Sertoli tubulobulbar complexes were found; some (12 in number) invaginated the reconstructed cell, while others (6) emanated from it. Of 37 round germ cells that were sectioned in their entirety and adjoined the reconstructed cell, 23 displayed desmosome-gap junctions with either the reconstructed cell or an adjoining cell. Since there were multiple junctions connecting some germ cells to Sertoli cells, the total number of junctions was much greater (35). Desmosome-gap junctions of the Sertoli cell were numerous connecting pachytene spermatocytes, less numerous connecting type B spermatogonia, and even less numerous connecting step 5 spermatids; and none was seen joining Sertoli cells with elongate spermatids. Most desmosome-gap junctions join germ cells to the body of the Sertoli cell at its basal aspect. Their numbers and position indicate that they play a role in the maintenance of the integrity of the seminiferous epithelium and may provide a route for cell-to-cell communication. Ectoplasmic specializations of the reconstructed cell were seen facing only 3 of 37 round germ cells, and 7 ectoplasmic specializations from adjoining Sertoli cells faced these germ cells, all of which were step 5 spermatids. That there were no ectoplasmic specializations facing pachytene cells indicates that ectoplasmic specializations are not acquired as these cells pass through Sertoli--Sertoli junctions, but are acquired later in spermatogenesis.