Central Hump Research Articles

Phymatoceros Stotler et al. (Anthocerotophyta) newly recorded from India with a new species, P. binsarensis

ABSTRACT Introduction Phymatoceros Stotler et al., one of the 14 extant genera of hornworts, is known from only two species worldwide. During our studies of Indian hornworts, a distinctly variable population was found at Binsar, Uttarakhand, and sharing the same habitat as Phaeoceros himalayensis (Kashyap) Prosk. ex Bapna & G.G.Vyas and Phaeoceros laevis (L.) Prosk. Methods A critical study of the specimens housed at CSIR–NBRI, Lucknow (LWG) was conducted. An SEM study of spores was also carried out to examine their ultramorphological characters. Key results The plants were found to be remarkably characterised by a narrow thallus with prolific stalked tubers arising from the mid-ventral surface; female plants with short involucres; single rounded to irregular chloroplast per cell, without a pyrenoid; and spore distal face with a large, central, single, pitted central hump, and the proximal face with a distinct single dimple on each tetrahedral area between triradiate rays. A detailed morphotaxonomic account is presented, along with detailed SEM observations of spores of the Indian plants. Conclusion Our critical comparative study has revealed that the plants of the newly recorded population belong to the genus Phymatoceros and are distinct from hitherto known species. They are described here as a new species, Phymatoceros binsarensis A.K.Asthana, D.Shukla & Reesa Gupta, and are the first record of Phymatoceros in India. As such, they represent a remarkable and interesting disjunct occurrence of the genus in Asia, separate from its distribution in four other continents (Africa, Europe, and North and South America).

Characteristics of Model-Free Pricing Kernels

This study combines model-free conditional estimators for the risk-neutral and the physical distribution of equity returns to obtain daily measures for the pricing kernel at the monthly time horizon. Despite their time-varying nature, our pricing kernels are non-parametric, forward-looking, agnostic about preferences, economic state variables or their dynamics and rely only on minimal technical constraints. Still, our realized pricing kernel estimates are clearly linked to economic state variables like the term spread, the credit spread or liquidity. We decompose the expected variance of the log pricing kernel and find that jumps contribute a considerable portion to overall pricing kernel risk. Building on statistical tests, we confirm an U-shape in the pricing kernel at all times and find a strong link between variations in its magnitude and the variance risk premium. A central hump in the pricing kernel can be confirmed unconditionally, but appears to fade during crisis times.

Deposition Behavior of Nanostructured WC–23Co Particles in Cold Spraying Process

The nanostructured WC–23Co particles were deposited on three kinds of substrates in different accelerating gas temperature by using cold spraying process. The morphologies of nanostructured WC–23Co splats attached on the polished surface of different substrates were characterized via scanning electron microscopy. It is revealed that the splats are partially embedded in Q235 and stainless steel with a comparative integrated contour similar to that of the original particles. There exist some revers around the splats and some corrugations or ripples on the Q235 and stainless steel substrates. In contrast, the splats on the surface of WC–12Co substrate present clearly a flat shape with central hump surrounded by a ringy band. By comparison of the morphologies of splats deposited on three kinds of substrates with the accelerating gas temperature of 850 ± 10°C and 750 ± 10°C, it can be found that the deformation of nanostructured WC–23Co particles is enhanced by the increment of substrate hardness and gas temperature.

Differences Between Chondrocytes and Bone Marrow-Derived Chondrogenic Cells

Implantation of autologous chondrogenic cells has become the mainstay strategy for repairing articular cartilage defects. Because the availability of autologous chondrocytes is extremely limited, many recent studies have used artificially induced mesenchymal stem cells (iMSCs) as substitutes for chondrocytes. In this study, we analyzed the differences between the iMSCs and chondrocytes, including their molecular biological and mechanical properties. Human bone marrow-derived MSCs were collected and induced to exhibit the chondrogenic phenotype by culturing the pelleted MSCs in a chemically defined culture medium supplemented with transforming growth factor-beta 1. The molecular biological properties of iMSCs and culture-expanded chondrocytes, including their mRNA profiles and surface proteomics, were analyzed using reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry, respectively. The biomechanical properties of iMSCs and native chondrocytes, including their surface topology, adhesion force, and membrane stiffness, were analyzed using atomic force microscopy (AFM). Both iMSCs and chondrocytes presented type II collagen and glycosaminoglycan, whereas only chondrocytes presented type X collagen. Flow cytometric assays showed that the expression of type II collagen and integrin-1 was higher in the chondrocytes than in the iMSCs. AFM revealed that the MSCs, iMSCs, and chondrocytes greatly differed in their shape. The MSCs were spindle shaped and easily distinguishable from the spherical chondrocytes. The iMSCs appeared round and resembled the spherical chondrocytes; however, the iMSCs were flatter with a central hump of condensed mass and a surrounding thin and broad pleat. The mean adhesion force and mean surface stiffness were significantly lower for the iMSCs (4.54 nN and 0.109 N/m, respectively) than for the chondrocytes (6.86 nN and 0.134 N/m, respectively). To conclude, although the iMSCs exhibited the chondrogenic phenotype, they differed from the chondrocytes in their molecular biological and mechanical properties.

An Interpretation of Langmuir Probe Floating Voltage Signals in a Cutting Arc

An experimental study of the electrostatic probe floating voltage signals in a cutting arc and its physical interpretation in terms of the arc plasma structure is reported. Sweeping electrostatic probes have been used to register the local floating potential and ion current at 3.5 mm from the nozzle exit in a 30-A arc generated by a high energy density cutting torch with a nozzle bore radius of 0.5 mm and an oxygen mass flow rate of 0.71 g ldr s-1. It is found that the floating potential signal presented a central hump with duration almost similar to that corresponding to the ion current signal but having also lateral wings with much larger duration. Capacitive coupling between the probe and the conducting body of the nozzle and arc as a source for the floating potential signal was discarded. It is assumed that the hump in these probe voltage signals results from the presence of an electrostatic field directed in the radial direction outward the arc axis that is caused by thermoelectric effects. The probe floating voltage signal is inverted using the generalized Ohm's law together with the Saha equation, thus obtaining the radial profiles of the temperature, particle densities, radial electric field, and potential of the plasma at the studied section of the arc. The resulting temperature and density profiles derived from our interpretation are in good agreement with the data published elsewhere in this kind of high-pressure arcs. There is not a straightforward connection between the measured hump amplitude in the floating signal (ap4 V) and the derived increase in the plasma potential between the arc edge and the arc center ( ap10 V), due to the global zero current balance condition established by the finite size of the probe. It is shown, however, that the probe takes a floating potential value close to that corresponding to the plasma temperature at the probe center.

MRI findings in Dyggve‐Melchior‐Clausen syndrome, a rare spondyloepiphyseal dysplasia

We present the case of an 8-year-old female patient with bone dysplasia as part of Dyggve-Melchior-Clausen syndrome (DMCS). MRI was used to evaluate the case. In the spine, odontoid apophysis aplasia was found with no ossification nucleus, vertebrae with central hump, disk protrusions, hypertrophy of the posterior common vertebral ligament, and hidden spina bifida at the S4 level. Morphological anomalies were found in the hips both in the proximal femoral epiphysis, which was located excentrically and laterally to the femoral neck, and in the Y-cartilage, which was greatly enlarged. In the knees, anterior crossed ligaments were not seen, although there were some indirect signs that indicated congenital absence, including hypoplasia of the femoral trochlea and the intercondylar notch. There was bilateral medial patellar plicae and asymmetry in the height of the distal femoral and proximal tibial physes, as well as dysplasia of the facets of the patella. In comparison with radiography, MRI provides a much clearer definition of the aspects of bone dysplasia that are related to DMCS, including morphological changes in the soft tissue and cartilage of the spine, hips, and knees. MRI can enhance our understanding of the pathogenesis and evolution of deformities.

X linked spondyloepiphyseal dysplasia: a clinical, radiological, and molecular study of a large kindred.

X linked spondyloepiphyseal dysplasia (SEDT) is a rare disorder characterised by disproportionate short stature and degenerative changes in the spine and hips. We report a large kindred with 11 affected males and 17 obligate carrier females. We examined clinically and radiographically the seven living affected males and obtained detailed historical information on the four dead. The natural history was characterised by normal growth until late childhood. Decreased growth velocity was the earliest detectable abnormality. In adulthood, four subjects required hip replacements but disability was minimal. Clinical examinations showed a characteristic habitus with short stature (> 2 SD below the mean) and a decreased upper segment to lower segment ratio (> 1 SD below the mean) in all affected subjects. Also noted were scoliosis (6/7), and decreased range of hip rotation (6/7), and decreased range of movement of the lumbar spine (4/7). Radiographic evaluations were available on nine subjects. Radiographic changes were evident in two patients in childhood; findings in adulthood included narrow disc spaces (8/9), platyspondyly (7/9), the characteristic central and posterior hump of the vertebral bodies (6/9), bony spurs (7/ 8), and pelvic abnormalities (7/9). We also systematically evaluated eight obligate carrier females. They could not be distinguished from the general population on clinical and radiographic findings. Linkage analysis showed significant linkage with markers on Xp22, as previously reported. A recombinant event between DXS43 and DXS207 places the locus distal to DXS43.

Detection of artificially created negative ion clouds with incoherent scatter radar

Theoretical incoherent scatter (IS) spectra from collisionless F region plasma are calculated taking into account the effect of negatively charged ions. Such ions can significantly change the composition of the local ionosphere when they are created artificially during active chemical release experiments. If IS radar observations are conducted upon such a modified plasma, the interpretation of the scattered radar signal will be complicated by the negative ions, which are not found in the natural (e.g., O+/e−) ionosphere. Specifically, the presence of heavy negative ions will broaden the IS spectrum, making the shoulder peaks sharper, and creating an additional small central hump. A radar spectral analysis program that assumes only the naturally occurring plasma constituents will erroneously attribute such spectral changes to changes in other plasma parameters, such as the temperature ratio Te/Ti. In order to detect heavy negative ions we fix the temperature structure of the ionosphere to a preevent average measurement and interpret any changes in spectral shape during the experiment as being caused by changes in composition, and not by changes in Te/Ti. The Millstone Hill 440‐MHz IS radar was used to observe the spatial and temporal development of heavy negative ion plasma clouds created during four active chemical release experiments: the Ionospheric Modification Study (IMS) in 1983, the Space‐Plasma Negative Ion Experiments (SPINEX 1 and 2) in 1984 and 1986 (all SF6 releases), and NICARE 1 in 1989 (CF3Br release). Each experiment led to the creation of a region of heavy, negatively charged ions. Concentrations of 10–40% SF6− (146 amu) are reliably detected in the SPINEX 1, SPINEX 2 and IMS data sets. An average uncertainty of ±10% SF6− is present in all three experiments. Concentrations of 30% Br− (80 amu) are further detected in the NICARE 1 release, with uncertainties of ±4%.

Solitons in Newtonian Gravity and Non-Linear Pancake Evolution

It is shown that the solutions for the non-linear equations governing the motion of a stratified self-gravitating isothermal fluid are generated by a sine-Gordon equation (SG) which has well-known soliton solutions. Starting with two solutions of the SG-equation which are related via an auto-Baecklund-transformation, the physical quantities, density, velocity and gravitational potential are expressed in a parametric form in terms of characteristic coordinates. The zero-solution and the one-soliton solution of SG generate a single hump in the density moving with constant velocity. The typical non-linear feature is the relation between amplitude A and width (y = square of the speed of sound). The 1-soliton together with the 2-sollton solution of SG produces two moving humps in the density which come to rest asymptotically. As a result of the interaction the ratio amplitude/width is different from the corresponding ratio of the single soliton. Due to a certain exchange symmetry in the transformation procedure relating the SG to the gravity system it is possible to generate another solution out of the 2-soliton. Which represents a single hump moving on a homogeneous background. The remarkable property is that the density becomes infinite in a finite time depending on the amplitude. The “breather”-solutlon of SG produces a density distribution that represents two pulses colliding onto a central hump at rest which are separated from each other by a discontinuity in the density and the velocity field. These solutions may have applications to the non-linear evolution of flat structures arising in the process of galaxy formation.

The α-cluster hypernuclei 5ΛHe, 6ΛΛHe, 9ΛBe, 10ΛΛBe and hypernuclear interactions

Variational calculations for 6 ΛΛ He, 9 Λ Be and 10 ΛΛ Be have been made with n α α - n Λ Λ cluster models. Various αΛ potentials are considered, all of which reproduce B Λ ( 5 Λ He ) . Some of the V αΛ are obtained from an αΛ model by a folding procedure using effective ΛN and ΛNN forces; realistic V αΛ are also obtained from 4N-Λ Monte Carlo variational calculations of 5 Λ He. These MC V αΛ include many-body effects which give a central hump even with only Λ N forces. 9 Λ Be is overbound by about one MeV with realistic αα and αΛ potentials, even with reasonable estimates of ΛN exchange effects which give a reduction ≅0.5 MeV. Repulsive ΛNN forces which can account for the overbinding of 5 Λ He give rise to a repulsive ααΛ potential which brings the calculated B Λ ( 9 Λ Be ) into good agreement with the experimental energy. The ΛΛ interaction strengths are obtained from 6 ΛΛ He and 10 ΛΛ Be for a number of ΛΛ potential shapes. The strengths obtained from 10 ΛΛ Be underbind 6 ΛΛ He by more than one MeV for all our ΛΛ and αΛ potentials. The ΛΛ interaction obtained from the well established ΛΛ 10 Be event is found to be quite strongly attractive, comparable to the 1 S 0 NN interaction without OPE, with correspondingly large negative ΛΛ scattering lengths of ≅ −4 to −5 fm.

Vibrational analysis of the hydrogen maleate ion using scaled ab initio force constants

The force field calculated under the ab initio scheme (4–31 basis set) was used to compute (GF formalism) the vibrational frequencies of the hydrogen (and deuterium) maleate (HM) ion in C 2υ symmetry. The scaling factors used to obtain a satisfactory fit to experimental frequencies were within acceptable limits. For the S 5 and S 6 symmetry coordinates (symmetric and antisymmetric OHO stretching) the force constants had to be empirically determined to fit the preassigned frequencies because the proton potential function has a central hump and thus the calculation yields a negative force constant for the S 6 coordinate.The assignments explain well the i.r. and Raman spectra as well as the INS data.

Perturbative technique as an alternative to the WKB method applied to the double-well potential

We give an explicit and complete perturbation theoretical analysis of the solutions and the eigenvalues of the Schrödinger equation for the double-well potential. In particular we demonstrate the matching of various branches of the solutions over the entire range of the independent variable, and we calculate the splitting of eigenvalues due to the finite height of the central hump of the potential.

The microwave spectrum of methyl isothiocyanate

New measurements of microwave transitions of CH 3NCS in the region 14–40 GHz are reported. Assignments of several sets of lines in terms of the transitions expected for a pseudosymmetric-top molecule are suggested and a tentative extension of the analysis to cover all the k = 0 lines in our spectra and in the region 5–11 GHz is proposed. Preliminary calculations using a two-dimensional anharmonic oscillator model lead to a bending potential with a central hump of some 160 cm −1, and a minimum-energy configuration at a CNC bond angle of about 147°. A correlation between rovibrational energy levels of a two-dimensional anharmonic oscillator and those of an asymmetric-top molecule with a bent skeleton and freely rotating methyl group is proposed.

Low-frequency bending motions of the silyl pseudohalides SiH3NCY (Y = O, S, Se). An experimental and theoretical study

We report the observation of far-infrared bands assigned to fundamental and overtone transitions involving the low-frequency bending motions of the title compounds and the simulation of the spectrum of silyl isocyanate using energy levels deduced from a potential function involving a pure quadratic well with a central hump of Lorentzian form. The observed spectra enable this potential to be specified to a higher level of precision than earlier indirect measurements.

Camel's back excitons in GaP

The influence of the recently proposed camel's back structure of the GaP conduction band edge on the exciton spectrum is investigated theoretically. The results are in good agreement with differential absorption data and strongly support a camel's back structure, with a 4 meV central hump. The computed exciton binding energy is 18.5 meV, and when combined with recent experimental data, indicates a binding of about 32 meV for the electron-hole liquid.

The two-dimensional anharmonic oscillator

Abstract Newly observed data on the rotational constants of carbon su☐ide in excited vibrational states of the low-wavenumber bending vibration ν 7 have been successfully interpreted in terms of the two-dimensional anharmonic oscillator wavefunctions associated with this vibration. By combining these results with published infrared and Raman spectra the vibrational assignment has been extended and a refined bending potential for ν 7 has been derived: this has a minimum at a bending angle of about 24° at the central C atom, with an energy maximum at the linear configuration some 23 cm −1 above the minimum. From similar data on the combination and hot bands of ν 7 with ν 4 (1587 cm −1 ) and ν 2 (786 cm −1 ) the effective ν 7 bending potential has also been determined in the one-quantum excited states of ν 4 and ν 2 . The effective ν 7 potential shows significant changes from the ground vibrational state; the central hump in the ν 7 potential surface is increased to about 50 cm −1 in the v 4 = 1 state, and decreased to about 1 cm −1 in the v 2 = 1 state. In the light of these results vibrational assignments are suggested for most of the observed bands in the infrared and Raman spectra of C 3 O 2 .

Cooperative Phenomena in the Triangular Lattice

A three-point triangle cluster and a W-shaped five-point cluster are used as the bases of the cluster-variation method in the triangular lattice, and the results are used to predict the properties to be obtained by the rigorous calculation. The following systems are treated using the same mathematical formulations: (a) the lattice-gas—liquid system, (b) the phase-separating binary alloy, and (c) the Ising model. In the pressure-versus-density isotherm of (a), the van der Waals-type loop shrinks as the approximation is improved and shows a tendency to approach the flat coexisting line. The central hump of the excess free energy in (b) lowers as the approximation is improved, and tends toward the flat line connecting the minima of the free-energy curve. The free energy of the Ising model (c) as a function of the long-range order parameter behaves in the same manner. When the binary alloy system (b) is quenched, the central hump remains in the free-energy curve (i.e., it does not become flat) in the rigorous treatment. It is pointed out that this nonequilibrium free energy is the quantity to be used in the treatment of the spinodal decomposition.

Fundamental Absorption Bands of the Deuteroammonias

The four fundamental vibration bands of N${\mathrm{D}}_{3}$ have been observed in infrared absorption, ${\ensuremath{\nu}}_{3}$ being a double band as in N${\mathrm{H}}_{3}$. The frequencies of the parallel vibrations, expressed in ${\mathrm{cm}}^{\ensuremath{-}1}$, are ${\ensuremath{\nu}}_{1}=2420$, ${\ensuremath{\nu}}_{3}=749.2 \mathrm{and} 745.8$, and of the perpendicular vibrations, ${\ensuremath{\nu}}_{2}=2556$ and ${\ensuremath{\nu}}_{4}=1191.3$. The rotational structure for ${\ensuremath{\nu}}_{3}$ is completely resolved. The perpendicular bands consist of many components with zero branches spaced at intervals of 1.7 ${\mathrm{cm}}^{\ensuremath{-}1}$ in ${\ensuremath{\nu}}_{2}$ and 5.2 ${\mathrm{cm}}^{\ensuremath{-}1}$ in ${\ensuremath{\nu}}_{4}$. The former cannot be resolved: they coalesce into a broad central absorption region, but the spacing of the most intense rotation lines in the composite band indicates the interval between centers. These frequency intervals agree well with the predictions of Johnston and Dennison. The moments of inertia for N${\mathrm{D}}_{3}$ are determined from the structure of the band ${\ensuremath{\nu}}_{3}$, by comparison with observations upon N${\mathrm{H}}_{3}$. They are $C=8.985\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}$ g ${\mathrm{cm}}^{2}$ with respect to the symmetry axis, and $A=5.397\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}$ g ${\mathrm{cm}}^{2}$ for any perpendicular axis. From these the molecular dimensions are obtained. The height of the pyramid is 0.360\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ cm and the distance between hydrogen atoms is 1.645\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ cm. New information regarding the potential curve is obtained (1) from observations upon the doubling of the first excited levels in the four varieties of ammonia, and (2) from the positions of higher excited levels in N${\mathrm{D}}_{3}$. Four vibration levels are located which lie above the central potential hump, and correspond to oscillations of the nitrogen atom from side to side through the plane formed by the hydrogen atoms.