Transverse Approaches Research Articles

Transverse momentum dependence of directed particle flow at160AGeV

The transverse momentum ($p_t$) dependence of hadron flow at SPS energies is studied. In particular, the nucleon and pion flow in S+S and Pb+Pb collisions at 160 AGeV is investigated. For simulations the microscopic quark-gluon string model (QGSM) is applied. It is found that the directed flow of pions $v_1(y, \Delta p_t)$ changes sign from a negative slope in the low-$p_t$ region to a positive slope at $p_t \geq 0.6$ GeV/c as recently also observed experimentally. The change of the flow behaviour can be explained by early emission times for high-$p_t$ pions. We further found that a substantial amount of high-$p_t$ pions are produced in the very first primary NN collisions at the surface region of the touching nuclei. Thus, at SPS energies high-$p_t$ nucleons seem to be a better probe for the hot and dense early phase of nuclear collisions than high-$p_t$ pions. Both, in the light and in the heavy system the pion directed flow $v_1(p_t, \Delta y)$ exhibits large negative values when the transverse momentum approaches zero, as also seen experimentally in Pb+Pb collisions. It is found that this effect is caused by nuclear shadowing. The proton flow, in contrary, shows the typical linear increase with rising $p_t$.

Postoperative morbidity in the morbidly obese parturient woman: Supraumbilical and low transverse abdominal approaches

Objective: Our purpose was to determine the differences in postoperative morbidity in obese women who had a supraumbilical or a Pfannenstiel incision at cesarean delivery. Study Design: A case-control retrospective review was conducted of all patients who were at >150% ideal body weight when undergoing cesarean delivery between 1989 and 1995 by means of either a supraumbilical or a Pfannenstiel incision. Patients were excluded if medical records were unavailable. A total of 15 women who had a supraumbilical incision and 54 who had a low transverse incision were included in the analysis. Antenatal complications were examined, as were age, weight, and training level of the surgeon. Postoperative complications were then compared. Results: The groups were similar in age and antepartum complications. However, mean weight and percentage of ideal body weight in the supraumbilical group were both higher ( P < .00001 and P < .0001, respectively), with the supraumbilical group 83 lb heavier on average. No significant differences were seen in any postoperative complication. Conclusion: Postoperative morbidity in morbidly obese women undergoing cesarean delivery does not differ between a supraumbilical approach and the low transverse abdominal incision. (Am J Obstet Gynecol 2000;182:1033-5.)

The general fundamental solution of the sixth-order Reissner and Mindlin plate bending models revisited

The sixth-order differential equation system of the Reissner and Mindlin plate bending models describe mathematically the plate problem, where lines normal to the mid-plane before deformation remain straight and inextensible in the deformed configuration, but not necessarily normal to the reference plane anymore. The non-normality condition is due to the consideration of transverse shearing strains, disregarded in the classical bi-harmonic Kirchhoff plate model. As the plate thickness is reduced and/or the transverse shear modulus is increased, the deformed configuration is less dependent of the transverse shear strains and, in the limit as the plate thickness approaches zero and/or the transverse shear modulus approaches ∞, the transverse shear strain effects vanish and the problem is exactly that described by the classical plate model. In this paper, we investigate the fundamental solutions of both the fourth-order Kirchhoff and the sixth-order Reissner and Mindlin plate models. We consider a transversely isotropic material and show that the fundamental solution of the bi-harmonic problem can be obtained directly from the general fundamental solution of the sixth-order plate problem, in the limit as the plate thickness approaches zero and/or the transverse shear modulus approaches ∞. This solution is in agreement with the analytical solution of an infinite thin clamped circular plate submitted to a unitary concentrated load acting at its center.

Ultrasound-Guided Cryotherapy for Retinal Tears in Patients With Vitreous Hemorrhage

The goal was to utilize ultrasound-guided cryotherapy as an immediate, low-risk, noninvasive, precise method of treating retinal tears obscured by vitreous hemorrhage. Eleven patients with sudden onset of vitreous hemorrhage were referred for diagnosis and management. Ophthalmoscopy with scleral depression was unsuccessful at localizing peripheral retinal tears, and all of the patients were examined with ultrasound using the techniques of standardized echography. The cryoprobe was positioned for cryotherapy using both transverse and longitudinal B-scan approaches following the indentation of the globe as it appeared on the oscilloscope. On follow-up examination after the vitreous hemorrhage cleared, 10 of the 11 tears were examined by ophthalmoscopy and were thought to have been adequately treated. One patient had a retinal detachment after remaining stable for 3 months. Two patients were treated with laser to enhance the cryotherapy seal. One patient was observed by another physician and underwent vitrectomy due to vitreous hemorrhage that persisted 2 months following cryotherapy. After vitrectomy, the physician reported a successful cryotherapy reaction at the treated tear. One final patient in the series required vitrectomy and scleral buckle before the hemorrhage had cleared, and the treatment did not appear to be complete. Ultrasound-guided cryotherapy provides a noninvasive, inexpensive treatment alternative for retinal tears obscured by vitreous hemorrhage.

Videotunneler for minimal and direct access aortoiliac reconstructive surgery.

Despite improvements in surgical practice and postoperative care, the large vertical midline or transverse transperitoneal approaches used in abdominal aortic surgery are still associated with a relatively high perioperative morbidity and mortality rate even in patients who are considered good risks for undergoing aortic surgery. This significant perioperative morbidity is partly caused by the major surgical trauma. To decrease the surgical stress on these patients we have developed a less-extensive procedure for this type of vascular reconstruction. The abdominal aorta is explored using a special retractor through a short upper median minilaparotomy utilizing modified conventional surgical hand instruments. For an aortobifemoral graft implantation, a retroperitoneal tunnel is necessary. During the creation of this tunnel special care should be exercised to avoid troublesome hemorrhage with iliac and other vein lacerations. To overcome these difficulties, we have developed a new tunneling device, which allows us to have visual control of the tunneling procedure. This prototype device contains a semiflexible tube with an inflatable balloon and a flexible videoendoscope. It is introduced along the external iliac artery into the retroperitoneal space and creates a tunnel through step-by-step inflation of the balloon. After this, the graft is implanted in the usual manner. To date, 19 abdominal vascular reconstructions have been performed with this method.

Retroperitoneal "Mini" Approach for Aortoiliac Reconstructive Surgery

The large vertical midline or transverse transperitoneal approaches used in the conven tional aortoiliac reconstruction are accompanied with a relatively high postoperative morbidity and mortality rate (2% to 5%), even in patients who are good risks under going aortic surgery. The purpose of this study was develop a new technique for aorto bifemoral bypass operation to minimize the operative stress on these patients. Methods: The recommended left paramedian or transmuscular retroperitoneal approach, using 5-6 cm skin incision and a special retractor with three-dimensional vision and with modified surgical instruments directly under eye control, offers the possibility of decreasing the operative stress significantly and of sufficiently controlling the serious bleeding that might occur. If necessary, this exposure can be immediately converted to a conventional approach by simple enlargement of the incision. Results: In the authors' first cases the functional results were very good, and conse quently, hospitalization time and the convalescence period were short. Conclusion: This minimal access approach appears to diminish the catabolic response, and it is hoped that it will be associated with accelerated recovery and virtual abolition of large wound-related complications. It could become the procedure of choice for selected patients with obstructive or aneurysmal aortoiliac disease.

Equivalent transverse shear stiffness of honeycomb cores

This work deals with the influence of geometry on the equivalent transverse shear stiffness of honeycomb sandwich plates. First, it presents the analytical solution for a two-dimensional basic cell of honeycomb structures by the two scale method of homogenization for periodic media. This solution gives the first order equivalent transverse shear modulus of honeycomb structures. Then the equivalent transverse shear stiffness of a regular honeycomb core is evaluated by the unite element method using a three-dimensional basic cell and the analytical solution for honeycomb structures. The equivalent transverse shear stiffness of a honeycomb core, in general, depends on the geometry of the sandwich plate. However, when the core depth is large compared to the hexagonal size, the aspect ratio of face panel thickness to hexagon wall thickness has little influence, and the transverse shear stiffness approaches the solution of honeycomb cellular structures. Based on the numerical study, an improved lower limit for the equivalent transverse shear stiffness of honeycomb cores is proposed, and an improved local shear stress of honeycombs is presented.

Quantum phase transitions in XY spin models.

The ground state of an $\mathrm{XY}$ model changes at a critical transverse field, above which there is a gap from the fully polarized ground state to the first excitation. We investigate the phase transition from this ``Mott insulator'' phase as the transverse field approaches its critical value. We calculate exactly some Green's functions and critical exponents for $d$-dimensional ferromagnetic lattices and for the Sherrington-Kirkpatrick spin-glass model. Finite-dimensional spin glasses are also discussed.

Surface orientation of polypropylene. I. Theoretical considerations for the application of internal reflection spectroscopy

AbstractA theoretical consideration of the orientation of the transverse magnetic and the transverse electric polarization vectors of the evanescent field in attenuated total reflection spectroscopy was made. It was demonstrated that near the critical angle of total reflection the transverse magnetic polarization vector approaches a purely normal orientation to the interface between the sample and internal reflection element surfaces, while the transverse electric vector is parallel to this interface. With an appropriate experimental design a set of three orthogonal electric vectors can be obtained for the analysis of surface orientations. A method to obtain high‐quality infrared spectra of polypropylene surfaces at a fraction of a degree above the critical angle was developed using a KRS‐5 internal reflection element specially cut with a 40° entrance aperture. The surface orientation of uniaxially extended polypropylene films was studied by using the proposed experimental design. It was shown that the orientation of the helix axis of the macromolecular chains of polypropylene could be qualitatively detected. A method employing the 841‐ and 809‐cm−1 bands of polypropylene was used to show that the ratio of absorbances of these bands reflects the surface orientation of the uniaxially extended polypropylene films for a set of films extended 0–500%.

A semi-empirical pressure analysis for anatomy constrained by elastic support

A mathematical foundation is developed for the computation of pressures exerted on portions of the anatomy constrained by elastic fabric support. General formulae are derived for curvatures of an ellipsoidal model corresponding to orthogonal tension components at the point of measurement. It is found that the pressure contributions from both tension components are significant to first order in the longitudinal variation of circumference over an axial test zone, because, while the transverse curvature approaches the zeroth order cylindrical approximation, its longitudinal counterpart does not.

Thermal expansion behaviour of hydrostatically extruded linear polyethylene

The thermal expansion behaviour of a series of oriented linear polyethylenes has been measured over the temperature range −180 to + 70° C. With increasing deformation ratio the axial thermal expansion coefficient approaches that of the crystal unit cell, and the transverse expansion coefficient approaches that of the average in the crystal a- and b-axis directions. The implications of these results are discussed in terms of present understanding of the structure of these materials.

First observation of hadron production in e +e − collisions at 13 and 17 GeV CMS energy with the pluto detector at petra : Pluto Collaboration

First results from the magnetic detector PLUTO at the new e +e − storage ring PETRA are shown. The ratio R of the cross section for hadron production to that for μ-pair production has been measured to be R = 5.0 ± 0.5 at 13 GeV and 4.3 ±0.5 at 17 GeV. Both values have an additional systematic error of 20%. The events show a typical 2-jet structure. The mean transverse momentum approaches a constant value with increasing energy implying a shrinkage of the jet opening angle.

THE INFLUENCE OF RARE EARTH IONS ON FERRIMAGNETIC RESONANCE

本文利用关联函数的方法(久保理论),讨论了强交换耦合系统的亚铁磁共振,给出了系统总磁化率张量的一般表达式,由此可以定出铁磁支与交换支的共振场H0(或共振频率)和峯宽2△ω。所得结果表明,所谓快弛豫及慢弛豫机理不过是铁磁共振的两个分支(横分支与纵分支)。横分支相应于J及S的横向磁矩之间的耦合运动J,S分别为希土离子及铁离子的磁矩),而纵分支相应于J的纵向分量与S的横向分量之间的耦合运动。由于晶场及各向异性交换场的作用,J的量子化方向与S的量子化方向偏离一个角度φ。此外由于交换作用的各向异性,在交换作用哈密顿J·λ·S中,张量λ的非对角元可以相当大。结果表明,纵分支对峯宽的贡献近似地正比于φ2及λi3(i=1,2)。根据2△ω的一般表达式,在极低温下(4.2°K以下),峯宽主要是由横分支决定的。沿某些晶轴方向?a,当希土离子最低两个能级接近“交叉”时,共振场及峯宽应该出现反常峯值,这在实验上已经得到了证实。当温度升高时,纵分支将逐渐“压过”横分支。当纵向弛豫频率达到高频场的频率ω时,峯宽将出现极大值,一般实验中观察到的就是这个极大值。当温度继续升高时,横分支又将起主要作用。当横向弛豫频率接近相应于希土离子最低两个能级之间的间距ω21时(?=1),峯宽将出现第二个极大值。实验上只有沿希土离子最低两个能级接近交叉的方向进行测量时,才有可能观测到第二个峯值。当频率足够高,满足|ω21(?a)-ω|<<ω的条件时,在极低温下,将出现由横分支决定的尖锐的峯宽极大值。根据所得理论结果,除上述现象外,还可以统一地解释在希土石榴石铁氧体中观测到的下列实验事实:有效旋磁比随温度的显著变化;在抵消点附近峯宽的急剧上升;在镱铁氧体中观测到的在峯宽极大值出现的温度共振场显著上升等。指出了经典磁矩运动方程的局限性,在铁氧体中,晶场的作用与交换场其大小可以相比时,利用经典方程求解所得出的结果只能定性地解释某些与希土离子具体能级结构无关的现象。

Note on a fragment of a Teleosaurian snout from Kimmeridge Bay, Dorset

This piece of a Teleosaurian snout, which fell last winter from the cliff in Kimmeridge Bay, and was lately entrusted to me by J. C. Mansel, Esq., F.G.S., seems to me worthy of a short notice, as it is the first indication of this genus which, within Mr. Mansel9s knowledge, has been discovered at Kimmeridge; and I do not find in the British Museum any Teleosaurian fossils from this locality, nor are any mentioned in Mr. Seeley9s recent catalogue of the fossil Reptilia in the Woodwardian Museum, although in both these collections there are Teleosaurian remains from other Kimmeridge-clay localities. The fragment, 17 inches long, represents a very long and slender snout tapering gradually and slightly (its breadth decreases only 0·5 in. through a distance of 15-5 in.) to behind the external nostril, where the prmmaxillm suddenly and largely expand. The nostril, wholly inclosed in these bones, is dilated, strietly terminal, and directed obliquely forwards; its lower margin is interrupted by a prominent median tubercle formed of the swollen praemaxillary suture; and a shallow convex lobe projeets from the middle of the upper margin. The prmmaxillm ascend 2·5 in. above the nostril, and end in an acute point, the maxill· composing all the remainder of the fragment. The upper surface of the snout is convex transversely, more so in front than posteriorly, where it becomes depressed; but its transverse section nowhere approaches the semicircular form of the stouter-snouted 8teneosauru, Mansdii, which I described last session. The lateral margins are slightly

Note on a Fragment of a Teleosaurian Snout from Kimmeridge Bay, Dorset

T his piece of a Teleosaurian snout, which fell last winter from the cliff in Kimmeridge Bay, and was lately entrusted to me by J. C. Mansel, Esq., F.G.S., seems to me worthy of a short notice, as it is the first indication of this genus which, within Mr. Mansel's knowledge, has been discovered at Kimmeridge; and I do not find in the British Museum any Teleosaurian fossils from this locality, nor are any mentioned in Mr. Seeley's recent catalogue of the fossil Reptilia in the Woodwardian Museum, although in both these collections there are Teleosaurian remains from other Kimmeridge-clay localities. The fragment, 17 inches long, represents a very long and slender snout tapering gradually and slightly (its breadth decreases only 0·5 in. through a distance of 15-5 in.) to behind the external nostril, where the prmmaxillm suddenly and largely expand. The nostril, wholly inclosed in these bones, is dilated, strietly terminal, and directed obliquely forwards; its lower margin is interrupted by a prominent median tubercle formed of the swollen præmaxillary suture; and a shallow convex lobe projeets from the middle of the upper margin. The prmmaxillm ascend 2·5 in. above the nostril, and end in an acute point, the maxill· composing all the remainder of the fragment. The upper surface of the snout is convex transversely, more so in front than posteriorly, where it becomes depressed; but its transverse section nowhere approaches the semicircular form of the stouter-snouted 8teneosauru, Mansdii, which I described last session. The lateral margins are slightly