Identical Sheets Research Articles

Laboratory tests on ridging and rafting of ice sheets

The mechanical deformation of a sea ice cover takes place through ridging and rafting. These processes have been studied in an ice basin by pushing two identical ice sheets together. Nonuniform ice sheets consisting of floes of thickness t1 and thin ice of thickness t2 connecting the floes were used. The major thickness t1 and the thickness ratio t2/t1 were varied. Ice sheets of uniform thickness (t2/t1 = 1) never formed ridges; they only rafted. However, when ice sheets of nonuniform thickness were used, initial rafting transformed into ridging. In general, high values of t1 and low values for t2/t1 favored ridging, while low values of t1 and high values for t2/t1 favored rafting. The forces during the tests were measured. During the initial rafting stage the force increased linearly with displacement. The experiments also suggest that the ridging force has a maximum value. This limit can be related to horizontal growth of the ridge or onset of ridging in another site. The relation between force and ice sheet thickness has also been analyzed. Further, from the force and the measured ridge profiles it was possible to estimate the ratio of work to change in potential energy. This ratio was about 15 for ridging and about 35 for rafting.

Experimental Studies on Adaptive Fuzzy Control of a Smart Structure

The present investigation deals with the application of an Adaptive Fuzzy Control Algorithm for active vibration control of an experimental flexible beam. The two-dimensional model of the experimental cantilever beam, given by an orthogonal tetrahedral space truss, represents a slender cantilever aluminum (7075-T6) beam of rectangular cross-section (1145 × 60 × 1.95 mm3). A variety of transient disturbances are introduced to excite the first four modes of the beam. The resulting transverse displacements are observed by a single sheet (50 × 50 mm2) of piezoceramic material placed at the clamped end of the beam. Active control of the beam is provided by one, two or three identical sheets of piezoceramic material collocated with the sensor. The control moments applied by the piezoceramic actuator are made to emulate the behavior of a discrete dynamic vibration absorber. The virtual absorber is tuned to the fundamental frequency using classical methods and the tuning ratios are time-invariant. However, the uniqueness of this approach is that the damping parameters of the emulated absorber are continuously varied by means of a fuzzy logic control algorithm to provide near minimum-time suppression of vibration. It is demonstrated that application of this methodology allows for its real-time implementation and provides relatively quick settling times in the closed-loop.

2-Dimensional sheet structures from linked metal fluoride tetrahedra

Two 2-dimensional lithiumfluoroberyllate compounds, that possess identical anionic sheet topologies, have been synthesised from aqueous solutions under hydrothermal and ambient pressure conditions. The structures of [Li2Be2F8][C2N2H10], 1, and [Li2Be2F8][CH3NH3]2·[H2O]2, 2, consist of inorganic layers, constructed from linked [MF4] (M = Li, Be) tetrahedra with organic templating cations incorporated between the sheets. For the ethylenediammonium cation, 1, the structure is a C-centred monoclinic cell, (space group C2/c), whereas the methylamine hydrate, 2, crystallises in P21/c, The interlayer regions possess corrugated topologies within which the organic moieties lie with the amine groups directed into the larger pockets. Hydrogen bonding exists between ions situated on the protonated amine groups on the templating species and electronegative fluoride ions.

IVF treatments and their outcomes in Finland in the 1990s

In vitro fertilization and its variants have become routine infertility treatments in industrialized countries. Our purpose is to summarize the procedures and treatment outcomes in Finland in the 1990s and to compare the results between public and private clinics. The data came from the Finnish IVF statistics for 1992 to 1999. Most analyses were done for the years 1994 to 1998 for which identical data-collection sheets were used. In 1999, 12 of the 19 clinics offering assisted reproductive treatments were private. The number of treatments increased from 2,331 in 1992 to 7,213 in 1999. In total 58% were performed in the private sector. Most treatments were given for women aged 30 to 39 years, but in the private sector women were up to on average two years older. Most often care was given due to tubal factor or unexplained infertility (IVF) and due to male factor or multiple causes (ICSI). The number of transferred embryos decreased during the study period, but the transfer of two embryos was still most frequent. Three out of four IVF and ICSI pregnancies, and two out of three FET pregnancies ended in a live birth. The success rates improved for IVF and for ICSI after adjustment for the number of transferred embryos, but not for FET. Small but inconsistent differences were observed in the success rates between the private and public sectors. There was noticeable variation between clinics. The number of treatment cycles stabilized in the late 1990s. The success rates improved only slightly and the differences in outcome measures between private and public clinics were small. However, neither this nor the large clinical variation could be investigated more thoroughly without collecting individual register data.

Palm Computer Demonstrates a Fast and Accurate Means of Burn Data Collection

Manual biomedical data collection and entry of the data into a personal computer is time-consuming and can be prone to errors. The purpose of this study was to compare data entry into a hand-held computer versus hand written data followed by entry of the data into a personal computer. A Palm (3Com Palm IIIx, Santa, Clara, Calif) computer with a custom menu-driven program was used for the entry and retrieval of burn-related variables. These variables were also used to create an identical sheet that was filled in by hand. Identical data were retrieved twice from 110 charts 48 hours apart and then used to create an Excel (Microsoft, Redmond, Wash) spreadsheet. One time data were recorded by the Palm entry method, and the other time the data were handwritten. The method of retrieval was alternated between the Palm system and handwritten system every 10 charts. The total time required to log data and to generate an Excel spreadsheet was recorded and used as a study endpoint. The total time for the Palm method of data collection and downloading to a personal computer was 23% faster than hand recording with the personal computer entry method (P < 0.05), and 58% fewer errors were generated with the Palm method.) The Palm is a faster and more accurate means of data collection than a handwritten technique.

THE CRYSTAL CHEMISTRY OF URANYL MOLYBDATES. II. THE CRYSTAL STRUCTURE OF IRIGINITE

The structure of synthetic iriginite, [(UO 2 )Mo 2 O 7 (H 2 O) 2 ](H 2 O), a 6.705(1), b 12.731(2), c 11.524(2) A, V 983.6(3) A 3 , Z = 4, has been refined on the basis of F 2 for all unique data collected with monochromatic Mo K α X-radiation and a CCD-based detector. The agreement factor ( R 1) was 3.5%, calculated using 532 unique observed reflections (| F o | ≥ 4σ F ), and the goodness-of-fit ( S ) was 0.92. This study indicates that iriginite crystallizes in space group Pbcm , rather than Pca 2 1 as indicated in a previous investigation. The structure contains one symmetrically distinct U 6+ cation that is strongly bonded to two atoms of O, forming a nearly linear uranyl ion ( Ur ) coordinated by five additional atoms of O arranged at the equatorial corners of pentagonal bipyramids that are capped by the O Ur atoms. The single symmetrically distinct Mo 6+ cation is in a distorted octahedral coordination involving five atoms of O and one H 2 O group. The structure consists of symmetrically identical sheets of edge-sharing Ur ϕ 5 pentagonal bipyramids and Moϕ 6 octahedra (ϕ: unspecified ligand), with composition [(UO 2 )Mo 2 O 7 (H 2 O) 2 ] 0 . The sheets are linked together via H bonds involving interlayer H 2 O groups.

JUABITE, CaCu10(Te4+O3)4(AsO4)4(OH)2(H2O)4: CRYSTAL STRUCTURE AND REVISION OF THE CHEMICAL FORMULA

The crystal structure of juabite, CaCu 10 (Te 4+ O 3 ) 4 (AsO 4 ) 4 (OH) 2 (H 2 O) 4 , triclinic, a 8.9903(7), b 10.1197(8), c 8.9959(7) A, α 102.654(1), β 92.432(1), γ 70.432(1)°, V 752.0(2) A 3 , space group P 1, Z = 1, has been solved by direct methods and refined by least-squares techniques on the basis of F 2 for 3358 unique reflections collected for a microcrystal using graphite-monochromated Mo K α X-radiation and a CCD area detector. The agreement index ( R 1) was 7.3%, calculated for 2288 unique observed [ F ≥ 4σ F ] reflections, and the goodness-of-fit ( S ) was 1.03. The structure determination has shown that the formula originally proposed for juabite is incorrect with regards to the oxidation state of Te, as well as the absence of Ca. The structure contains five unique Cu 2+ positions that are each in square pyramidal coordination. The two symmetrically distinct Te 4+ cations are in the usual one-sided coordination owing to the presence of a lone pair of electrons on the cation; there are three short Te 4+ –O bonds with lengths ~1.9 A in each polyhedron, as well as two or three longer bonds. The structure contains two unique As 5+ cations that are tetrahedrally coordinated by O 2− anions, and one Ca position that is octahedrally coordinated by O 2− anions. Juabite possesses a layered heteropolyhedral framework structure; layers parallel to (010) are weakly bonded in the [010] direction, resulting in a perfect {010} cleavage. Each layer contains all of the cation polyhedra of the structure, and involves two symmetrically identical sheets that contain four of the Cuϕ 5 square pyramids [ϕ: O 2− , (OH) − , H 2 O], both Te 4+ ϕ n polyhedra, and both AsO 4 tetrahedra. The sheets are parallel to (010), and chains of edge-sharing CaO 6 octahedra and Cuϕ 5 square pyramids extending parallel to [001] are sandwiched between adjacent symmetrically identical sheets, such that all anions contained within the chains are also linked to the sheets on either side, resulting in the heteropolyhedral layers.

Networks with hexagonal circuits in co-ordination polymers of metal ions (ZnII, CdII) with 1,1′-(1,4-butanediyl)bis(imidazole)

Three new compounds, [ZnL1.5(H2O)(SO4)]·6H2O 1, [ZnL1.5(H2O)2][NO3]2·2H2O 2 and [CdL1.5(H2O)2(SO4)]·4H2O 3 were obtained from self-assembly of the corresponding metal salts with 1,1′-(1,4-butanediyl)bis(imidazole) (L). In both 1 and 2 zinc ion is five-co-ordinated, showing a less-common trigonal bipyramidal co-ordination polyhedron, while cadmium ion of 3 is six-co-ordinated with a common octahedral arrangement. The sulfate ions of 1 and 3 are co-ordinated, however the nitrate ions of 2 are not. Each of the three compounds is composed of a (6, 3) network with the hexagonal smallest circuit containing six metal ions and six L; each L is co-ordinated to two metal ions, acting as a bridging ligand. In 1 the 2-D sheet of (6, 3) networks is interpenetrated in an inclined mode by symmetry related, identical sheets to give an interlocked 3-D structure, while the (6, 3) networks of both 2 and 3 stack in a parallel fashion to construct frameworks having channels.

Risk factors for early death in acute ischemic stroke and intracerebral hemorrhage: A prospective hospital-based study in Asia. Asian Acute Stroke Advisory Panel.

In Asia, there has been no international study to investigate the risk factors for early death in patients with ischemic stroke and intracerebral hemorrhage. We conducted a prospective study of consecutive patients with acute stroke who were admitted to 36 participating hospitals in China, India, Indonesia, Korea, Malaysia, the Philippines, Singapore, Taiwan, Thailand, and Vietnam. With the use of a simple identical data sheet, we recorded the demographics and cardiovascular risk factors of each patient. Early death was defined as death on discharge from the acute hospital. We enrolled 2403 patients with ischemic stroke and 783 patients with intracerebral hemorrhage. Among patients with ischemic stroke, previous use of antiplatelet drugs (adjusted odds ratio [OR] 0.53; 95% confidence interval [CI] 0. 30 to 0.95) and relatively young age group 56 to 75 years (OR 0.65; 95% CI 0.42 to 1.00) were protective factors; atrial fibrillation (OR 2.23; 95% CI 1.40 to 3.57), ischemic heart disease (OR 2.03; 95% CI 1.37 to 3.05), diabetes (OR 1.52; 95% CI 1.04 to 2.22), and ex-smoker status (OR 2.18; 95% CI 1.18 to 4.05) were risk factors for early death. Among patients with intracerebral hemorrhage, hypertension (OR 0.56; 95% CI 0.38 to 0.82) and young age group 56 to 75 years old (OR 0.55; 95% CI 0.34 to 0.87) were associated with lower death rate, whereas diabetes (OR 1.74; 95% CI 1.01 to 2.98) was a risk factor for early death. In Asian patients with stroke, previous use of antiplatelet drugs nearly halved the risk of early death in patients with ischemic stroke, whereas atrial fibrillation, ischemic heart disease, diabetes, and ex-smoker status were risk factors for early death. Among patients with intracerebral hemorrhage, diabetes was associated with early death, whereas young age group and hypertension were associated with lower death rates, though no clear explanation for the hypertension association could be discerned from the data available.

Packing similarities of three isosteric molecules: 4,5-dichlorophthalic anhydride, 4,5-dibromophthalic anhydride and 5,6-dichlorobenzfurazan 1-oxide, including three polymorphs of 5,6-dichlorobenzfurazan 1-oxide.

4,5-Dichlorophthalic anhydride (CPA) lies on a twofold axis in space group C2/c; the molecules pack as stacks of two-dimensional sheets. Polymorph A of 5,6-dichlorobenzfurazan 1-oxide (CBF; systematic name 5,6-dichloro-2,1,3-benzoxadiazole 1-oxide) is isomorphous with CPA with disordered CBF molecules being pseudo-isosteric with the CPA molecule. Polymorph C of CBF has similar unit-cell dimensions but the arrangement of the molecules in the cell is different. 4,5-Dibromophthalic anhydride occurs in space group P1; in a structure derived from the CPA structure. The four structures all have similar two-dimensional sheets of molecules, but differ, in addition to the disorder of the CBF molecules, in the stacking of successive sheets. There are three polymorphs of 5,6-dichlorobenzfurazan 1-oxide. In all three the molecules are disordered about twofold or pseudo-twofold axes. In all three the molecules form chains involving similar Cl.O contacts along the direction of the twofold axis. In polymorphs A and C these chains form virtually identical two-dimensional sheets with inter-chain C-H.O, C-H.N and Cl.Cl contacts, but with different stacking arrangements between the sheets. In polymorph B the chains are associated in face-to-face pairs with the same face-to-face overlap as in A, at an average distance of 3.42 Å compared to an average distance of 3.38 Å in A (cf. Table 8); there are no two-dimensional sheets.

Rafting and ridging of thin ice sheets

Rafting and pressure ridging are important processes in the deformation of sea ice that occur when two ice sheets are pushed together. In this study a two‐dimensional computer model of the rafting and ridging process is used to simulate a situation in which two identical ice sheets are pushed together at constant speed. Each model ice sheet is composed of two thicknesses of ice. The ratio of the thicknesses is varied to obtain degrees of inhomogeneity. The accuracy of the simulations is assessed by comparison with a series of similar physical experiments performed in a refrigerated basin. Following this comparison, the computer model is used to perform an extensive series of simulations to explore the effect of the thickness and the thickness inhomogeneity of the model ice sheets on the likelihood of occurrence of ridging and rafting. During the simulations the energy consumption and forces are explicitly calculated. The energy consumed during the simulations is used to demonstrate the smooth transition between ridging and rafting that occurs when the homogeneity of the sheets is varied.

Women's smoking behaviour--caught by a cigarette diary.

This study explores women's smoking behaviour in relation to mood, activity and social context. A particular aim was to design a 'cigarette diary', useful for research as well as for practical purposes. Fifty male nurses and secretaries kept a diary for one to three typical work days. Diaries consisted of a set of identical sheets, each of which related to one cigarette. Pre-smoking mood and the context of smoking were carefully noted. It was hypothesized that smoking is positively related to perceived stress. Results partly supported this hypothesis, but they also showed that a majority of the cigarettes were smoked in a state of happiness and relaxation.

The Psycholinguistic Status of the Root in Modern Hebrew

In this paper we describe an experiment designed to reveal the psycholinguistic status of the root in Modern Hebrew. The experiment was motivated by the following factors: (1) Major morphological theories set word-based (WB) constraints on possible morphological grammars, and certain theories address the lexical storage vs. decomposition debate. Prominent advocates of WB theory support the elimination of the root from contemporary Hebrew grammar, assuming that the stem and not the root and the pattern are stored in the lexicon. (2) Empirical research on this question conducted by linguists and psycholinguists necessitates such an experiment. A review of the above concepts is followed by a report on our experiment. We gave a coloring task to four groups: university students who were native speakers of Hebrew; primary school pupils who were native speakers of Hebrew; university students who were native speakers of Arabic; and university students who were native speakers of Russian. All Ss were given an identical sheet containing sixteen clearly typed Hebrew words. Ss were instructed to selectively color letters according to their free will. Statistical processing of the coloring outcomes revealed that, as opposed to the statistical null (H 0 ) hypothesis, letters were not colored at random: native Hebrew speakers selected letters that constitute the root of the words; native Russian speakers were ignorant of the root structure; and the Arabic-speaking group fell in between. The coloring of letters following other linguistic and non-linguistic criteria resulted statistically non-significant

Itinerancy of Quasiequilibria in One-Dimensional Gravitating Systems

One-dimensional self-gravitating many-body systems consist of N identical parallel sheets which have uniform mass density m and infinite in extent in the (y, z) plane. We call the sheets particles in this paper. The particles are free to move along x axis and accelerate as a result of their mutual gravitational attraction. The Hamiltonian of this system has a form of where m, vi, and xi are the mass (surface density), velocity, and position of ith particle respectively.

Phosphorus Nitride P3N5

Pure, stoichiometric, hydrogen-free, and crystalline phosphorus nitride P3N5 has been obtained for the first time by reaction of (PNCl2)3 and NH4Cl between 770 and 1050 K. The compound has been characterized by elemental analyses, 31P and 15N MAS NMR, EXAFS, IR spectroscopy, X-ray powder diffraction, and electron microscopy. In the solid a three-dimensional cross-linked network structure of corner sharing PN4 tetrahedra has been identified with 2/5 of the nitrogen atoms bonded to three P atoms and 3/5 of the nitrogen atoms bonded to two P atoms. By electron diffraction (ED) and high-resolution transmission electron microscopy (HRTEM) two distinguishable modifications α-P3N5 and β-P3N5 have been identified which differentiate only by the stacking order of identical sheets similar to the polytypes of SiC.

Phosphorus Nitride P3N5: Synthesis, Spectroscopic, and Electron Microscopic Investigations

Pure, stoichiometric, hydrogen-free, and crystalline phosphorus nitride P3N5 has been obtained for the first time by reaction of (PNCl2)3 and NH4Cl between 770 and 1050 K. The compound has been characterized by elemental analyses, 31P and 15N MAS NMR, EXAFS, IR spectroscopy, X-ray powder diffraction, and electron microscopy. In the solid a three-dimensional cross-linked network structure of corner sharing PN4 tetrahedra has been identified with 2/5 of the nitrogen atoms bonded to three P atoms and 3/5 of the nitrogen atoms bonded to two P atoms. By electron diffraction (ED) and high-resolution transmission electron microscopy (HRTEM) two distinguishable modifications α-P3N5 and β-P3N5 have been identified which differentiate only by the stacking order of identical sheets similar to the polytypes of SiC.

Study of structurally efficient graphite-thermoplastic trapezoidal-corrugation sandwich and semisandwich panels

The structural efficiency of compression-loaded trapezoidal-corrugation sandwich and semi-sandwich composite panels is studied to determine their weight savings potential. Sandwich panels with two identical face sheets and a trapezoidal corrugated core between them, and semi-sandwich panels with a corrugation attached to a single skin are considered. An optimization code is used to find the minimum weight designs for critical compressive load levels ranging from 3,000 to 24,000 lb/in. Graphite-thermoplastic panels based on the optimal minimum weight designs were fabricated and tested. A finite-element analysis of several test specimens was also conducted. The results of the optimization study, the finite-element analysis, and the experiments are presented.

Impact-Damaged Graphite-Thermoplastic Trapezoidal-Corrugation Sandwich and Semi-Sandwich Panels

The results of a study of the effects of impact damage on compression- loaded trapezoidal-corrugation sandwich and semi-sandwich graphite-thermoplastic panels are presented. Sandwich panels with two identical face sheets and a trapezoidal corrugated core between them, and semi-sandwich panels with a corrugation attached to a single skin are considered in this study. Panels were designed, fabricated and tested. The panels were made using the manufacturing process of thermoforming, a less-commonly used technique for fabricating composite parts. Experimental results for unimpacted con trol panels and panels subjected to impact damage prior to loading are presented. Little work can be found in the literature about these configurations of thermoformed panels.

A PHYSICAL SCALE MODEL STUDY OF THE COMPARATIVE PERFORMANCE OF TWO MODES OF OPERATION FOR FIXED‐LOOP TURAM‐TYPE EM SYSTEMS1

AbstractThe results of a physical scale model study of the conventional mode of operation of fixed loop electromagnetic systems and an alternative mode called the tx‐parallel mode in which traverses are run parallel to the long axis of the rectangular transmitter loop are presented. The results show that over thick or dipping conductors, the tx‐parallel configuration provides coupling with the target which is comparable with that provided by the conventional configuration. In addition, the tx‐parallel configuration is shown to provide more consistent indications of the direction and magnitude of conductor dip. Over wide conductors, where separate conventional surveys are needed to define the opposite edges of such conductors, it is shown that only a single tx‐parallel survey is needed to locate both edges of the conductor.The tx‐parallel results were found to allow better resolution of the individual anomalies due to closely spaced parallel conductors.The tx‐parallel response of identical sheet conductors of opposite dip indicated that the response of the separate sheets could be recognized even when the two sheets were placed at zero separation. This was found to be due in part to spatial displacement of the individual current vortices within each conductor owing to their mutual repulsion.

Use of plexiglas sheets coated with wavelength-shifter dyes for detection of atmospheric Cherenkov radiation

A 900 cm 2 area plexiglas sheet coated with a thin film of a combination of wavelength shifter dyes is used for detection of atmospheric Cherenkov ultraviolet photons in extensive air showers at Cosmic Ray Laboratory, Ooty in southern India. The response of the coated sheet is compared with an otherwise identical but uncoated plexiglas sheet in showers of different primary energies and at different distances from the axes. It is shown that the coated sheet is an efficient detector of Cherenkov UV photons in showers of energies > 10 14 eV. Based on these observations it is suggested that an array of detectors made from plexiglas sheets, coated with wavelength-shifter dyes, with interseparations of about 50 m can be effectively used as a large area detector for studies of cosmic sources of gamma rays of energies > 10 13 eV. Using the relative timing technique such an array can provide a large collection area, good angular resolution and wide aperture. The advantages of this new technique, relative to conventional detectors such as large area reflectors for Cherenkov photons and arrays of particle detectors for air showers, are discussed.