bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Poincaré problem for a compressible medium
Authors: Gans Roger F. 
Published: March 2006

By the ‘Poincaré problem’ is meant the determination of the free oscillations of a contained rotating fluid, its velocity being linearized around a state of solid rotation. Compressibility requires one to introduce a basic thermodynamic profile as well as a basic velocity distribution. Here the temperature gradient has been supposed proportional to the adiabatic gradient, by introduction of a proportionality constant α (α = 0 in the isothermal case; α = 1 in the adiabatic case). In this formulation the system is reducible to a single second-order ordinary differential equation and its boundary condition.It is proved that if α = 1 the oscillation frequencies in the rotating system cannot equal plus or minus twice the rotation frequency. The negative case is pathological in the sense that there are solutions arbitrarily near the forbidden solution, and a solution curve of frequency as a function of rotation rate crosses the forbidden frequency.The basic system is expanded in terms of a power series in γ − 1, where γ is the ratio of specific heats. The zeroth-order set of equations is solved in terms of confluent hypergeometric functions, and a solvability condition on the first-order set gives frequency shifts as functions of α. Several zeroth-order frequencies have been calculated, together with four first-order frequency shifts.
Effect of ohmic dissipation on internal Alfvén-gravity waves in a conducting shear flow
Authors: Rudraiah N. , Venkatachalappa M. 
Published: March 2006

Internal Alfvén-gravity waves of small amplitude propagating in a Boussinesq, inviscid, adiabatic, finitely conducting fluid in the presence of a uniform transverse magnetic field in which the mean horizontal velocityU(z) depends on heightzonly are considered. We find that the governing wave equation is singular only at the Doppler-shifted frequency Ωd= 0 and not at the magnetic singularities Ωd= ± ΩA, where ΩAis the Alfvén frequency. Hence the effect of ohmic dissipation is to prevent the resulting wave equation from having magnetic singularities. Asymptotic solutions of the wave equation, which is a fourth-order differential equation, are obtained. They show the presence of the magnetic Stokes points Ωd= ± ΩA. The interpretation of upward and downward propagation of waves is also discussed.To study the combined effect of electrical conductivity and the magnetic field on waves at the critical level, we have used the group-velocity approach and found that the waves are transmitted across the magnetic Stokes points but are completely absorbed at the hydrodynamic critical level Ωd= 0. The general expression for the momentum flux is mathematically complicated but will be simplified under the assumption\[ \frac{\partial^2h}{\partial x^2}+\frac{\partial^2h}{\partial y^2}\gg \frac{\partial^2h}{\partial z^2}, \]wherehis the perturbation magnetic field. In this approximation we find that the momentum flux is not conserved and the waves are completely absorbed at Ωd= 0.The general theory is applied to a particular problem of flow over a sinusoidal corrugation and asymptotic solutions are obtained by applying the Laplace transformation and using the method of steepest descent.
Unstable waves on an axisymmetric jet column
Authors: Mattingly G. E. , Chang C. C. 
Published: March 2006

The growth of infinitesimal disturbances on an axisymmetric jet column is investigated theoretically and experimentally. The theoretical analysis is based upon inviscid stability theory, wherein axisymmetric, helical and double helical disturbances are considered from the spatial reference frame. In the jet flow field near the source, the mean velocity profile is observed to have a potential core and a thin, but finite, shear layer between the potential core and the quiescent ambient fluid. With downstream distance, the potential core diameter decreases and the shear-layer thickness increases. To incorporate these variations into the theory, a quasi-uniform assumption is adopted, whereby successive velocity profiles are analysed individually throughout the region in the jet flow where disturbances are observed to be small. The results of the theory indicate that initially, in the jet flow where the shear layer is thin and the potential core is larger, all disturbances considered are unstable. The dominant disturbance in the jet is an axisymmetric one. However, further downstream in the jet, where the half-breadth thickness of the shear layer is 55% of the potential core radius, a helical disturbance is found to dominate the axisymmetric and double helical modes. Nowhere in the jet flow field examined was the double helical disturbance found to be dominant. The cross-stream distributions of velocity and vorticity for the dominant disturbance modes are presented according to the spatial stability theory.The downstream development of the jet column and the characteristics of the disturbances amplifying on it were also studied in a water tank. No artificial stimulation of any particular disturbance was used. The experimental results show good agreement with the results of the theory in the region where the disturbances are small. However, conclusive confirmation of the switch in the hierarchy of dominant disturbances was not found. Half of the time the disturbance observed experimentally exhibits an axisymmetric character and the other half a helical one. This apparently is due to the similar spatial amplification rates experienced by both of these disturbance modes. It is concluded that this switching of dominant modes is, in large part, responsible for (i) the well-known natural drifting of disturbance characteristics in jet flows, and (ii) the wide variety of observations made in previous jet experiments.
Waves and wave resistance of thin bodies moving at low speed: the free-surface nonlinear effect
Authors: Dagan G. 
Published: March 2006

The linearized theory of free-surface gravity flow past submerged or floating bodies is based on a perturbation expansion of the velocity potential in the slenderness parameterewith the Froude numberFkept fixed. It is shown that, although the free-wave amplitude and the associated wave resistance tend to zero asF→ 0, the linearized solution is not uniform in this limit: the ratio between the second- and first-order terms becomes unbounded asF→ 0 with ε fixed. This non-uniformity (called ‘the second Froude number paradox’ in previous work) is related to the nonlinearity of the free-surface condition. Criteria for uniformity of the thin-body expansion, combining ε andF, are derived for two-dimensional flows. These criteria depend on the shape of the leading (and trailing) edge: as the shape becomes finer the linearized solution becomes valid for smallerF.Uniform first-order approximations for two-dimensional flow past submerged bodies are derived with the aid of the method of co-ordinate straining. The straining leads to an apparent displacement of the most singular points of the body contour (the leading and trailing edges for a smooth shape) and, therefore, to an apparent change in the effective Froude number.
Fluid shielding of low frequency convected sources by arbitrary jets
Authors: Balsa T. F. 
Published: March 2006

A low frequency asymptotic theory is proposed for the shielding of noise by jets of arbitrary cross-section. The results of the theory provide a qualitative explanation for the appearance of the quiet and noisy planes of a slot jet. The arguments in favour of this explanation are derived from a model problem in which a pulsating mass source is convecting along the axis of an infinitely long column of fluid of arbitrary cross-section. The jet velocity is represented by a uniform velocity profile (i.e. slug flow). The method of matched asymptotic expansions is applied to derive expressions for the acoustic pressure and the radiative power of the source.The solution for the elliptic jet indicates that the radiative power in the horizontal plane (containing the major axis) is less than that in the vertical plane (containing the minor axis). This difference in power varies with source Strouhal number and jet Mach number. The effects of jet temperature are also included in the analysis. The theoretical results are in good qualitative agreement with experimental findings for slot nozzles. The theory indicates that the noise shielding offered by jets is negligible at low frequencies and low Mach numbers.
Evidence for scale similarity of internal intermittency in turbulent flows at large Reynolds numbers
Authors: Van Atta C. W. , Yeh T. T. 
Published: March 2006

Some new measurements and a reassessment of previous data on statistical properties of the breakdown coefficients qr,l in high Reynolds number turbulence show the existence of a range of scale similarity for scales larger than those in the viscous range (l [ges ] 36η). The rate of variation of the probability density p(qr,l) with changing outer scale l/η decreases as l/η increases, becoming fairly insignificant for the largest values of l/η. Measurements of characteristic functions of the probability densities show a substantial degree of statistical independence for sequential adjoint values of qr,l, consistent with the small values of the correlation coefficients for these variables. The data for the moments of qr,l exhibit a behaviour very close to that predicted by the scale-similarity theory when only data for r [ges ] 36η are considered, i.e. data for smaller inner length scales are excluded. The moments and corresponding values of the parameters μp are in good agreement with our previous results and with some earlier data of Kholmyansky, but some rather large unresolved differences in the probability densities of qr,l are found on comparing the present data with those of Kholmyansky. The present measurements of breakdown coefficients for ζ1 = [uscr ]− 1∂u/∂t = ∂(In [uscr ])/∂tand ζ2 = U−1∂u/∂t the time derivatives of the streamwise velocity and its logarithm measured in the atmospheric boundary layer, resolve some previous questions concerning the sensitivity of the results obtained to the choice of positive variable, varying sampling rates and the values of external parameters.For low sampling rates, a systematic change in the shape of the probability densities p(qr,l) with varying digital sampling rate is found using either ζ1 or ζ2. For sufficiently high sampling rates, the probability densities are independent of the sampling rate; and invariant results are obtained when the sampling rate is at least one-quarter of the Kolmogorov frequency associated with the viscous length scale based on the turbulent dissipation rate. The probability densities p(qr,l) measured using either ζ1 or ζ2 are very similar to the corresponding spectra of ζ1 or ζ2 respectively. Comparison of the mean-square values of ζ1 and ζ2 with an extended form of Taylor's hypothesis shows that the variable ζ1 is not a good approximation to the true spatial derivative ∂u/∂x, and the use of such an approximation can lead to results that are both qualitatively and quantitatively incorrect.
A technique to identify and preserve the spinal accessory nerve during neck dissection
Authors: Chaukar D A , Pai A , D'Cruz A K 
Published: March 2006

Introduction: Preservation of the spinal accessory nerve during neck dissection should be the rule rather than the exception. Despite the presence of many described techniques to locate the nerve, a tedious dissection is often required; as a consequence, it remains vulnerable to damage.Method: We describe a novel method, not previously reported, based on identifying a constant vein which crosses the nerve. This aids in the nerve's early identification.Conclusion: Our method enables the surgeon to locate the nerve precisely and to avoid damage to it, thereby maximizing post-operative function.
Satisfaction with cosmesis following nasal manipulation: do previous fractures matter?
Authors: Supriya M , Clement W A , Ahsan F , Cain A J 
Published: March 2006

Objective: To determine if patients who have had multiple previous nasal fractures and who undergo manipulation of fractured nasal bones under general anaesthetic (MUA) are as likely to be satisfied with their post-operative nasal cosmesis as patients who have only sustained a single injury.Design: Telephone survey.Setting: District general hospital.Participants: Adult patients who had undergone MUA over the preceding three years.Main outcome measures: Patient satisfaction with nasal cosmesis and nasal airway and willingness to consider corrective surgery.Results: One hundred and two patients were contacted. Overall patient satisfaction with cosmesis and nasal airway was 82 and 77 per cent, respectively, with 15 per cent willing to consider a procedure to improve their nasal cosmesis and 12 per cent willing to consider a procedure to improve nasal airway. Twenty-three (22.5 per cent) gave a history of one or more nasal bone fractures, either treated or untreated, prior to the most recently treated injury. Patient satisfaction with cosmesis in this group was 65 per cent, compared with 87 per cent satisfaction in the single injury group (p = 0.03). No statistically significant differences were demonstrated when comparing these groups for: satisfaction with nasal airway (70 vs 80 per cent, p = 0.46); willingness to consider a procedure to improve cosmesis (26 vs 11 per cent, p = 0.16); and willingness to consider a procedure to improve nasal airway (17 vs 10 per cent, p = 0.46).Conclusions: A history of multiple previous nasal fractures does appear to alter patient satisfaction with the cosmetic outcome of nasal manipulation. These patients should be informed that they have a decreased chance of attaining a cosmetically acceptable result.
Myxofibrosarcoma of the neck
Authors: Udaka T , Yamamoto H , Shiomori T , Fujimura T , Suzuki H 
Published: March 2006

We report a rare case of myxofibrosarcoma arising in the neck. A 55-year-old man presented with a two-year history of left-sided, painless, submandibular swelling. Computed tomography and magnetic resonance imaging (MRI) revealed an 80 × 35 mm, well defined, lobulated, submandibular tumour extending to the parapharyngeal space. The tumour showed uniformly low intensity and marked hyperintensity in T1- and T2-weighted MRI scans, respectively, and was scarcely enhanced by gadolinium. A tentative diagnosis of lymphangioma or plunging ranula was made, and the patient underwent local injection of OK-432, which proved to be ineffective. Resection of the tumour was then performed via a transcervical approach. The tumour was histopathologically and immunohistochemically diagnosed as a low-grade myxofibrosarcoma. The patient's post-operative clinical course was uneventful, and the patient was free of disease 27 months after surgery. The pathology, clinical characteristics and treatment of myxofibrosarcoma are bibliographically reviewed.
Functional MRI correlates of the recall of unresolved life events in borderline personality disorder
Authors: BEBLO THOMAS , DRIESSEN MARTIN , MERTENS MARKUS , WINGENFELD KATJA , PIEFKE MARTINA , RULLKOETTER NINA , SILVA-SAAVEDRA ANAMARIA , MENSEBACH CHRISTOPH , REDDEMANN LUISE , RAU HARALD , MARKOWITSCH HANS J. , WULFF HELLA , LANGE WOLFGANG , BEREA CRISTINA , OLLECH ISABELLA , WOERMANN FRIEDRICH G. 
Published: March 2006

Background. Patients with borderline personality disorder (BPD) frequently report unresolved life events but it is still poorly understood, how these experiences are represented in the brain. Using functional magnetic resonance imaging (fMRI), the present study aimed at investigating the neural correlates of the recall of unresolved life events in patients with BPD and healthy controls.Method. Twenty female BPD patients and 21 healthy control subjects underwent fMRI. During measurement subjects recalled unresolved and resolved negative life events. Individual cue words were used to stimulate autobiographical memory. After scanning, subjects rated their emotional states during the recall of both types of memories.Results. When contrasting unresolved and resolved life events, patients showed significant bilateral activation of frontotemporal areas including the insula, amygdala, and the anterior cingulate cortex, the left posterior cingulate cortex, right occipital cortex, the bilateral cerebellum and the midbrain. In healthy subjects, no differential brain activation was related to these conditions. The 2×2 factorial analysis (ΔBPD−Δcontrols) revealed similar results with bilateral activation of the frontal cortex including parts of the insula and of the orbitofrontal cortex, temporal activation including the amygdala, activation of the right occipital cortex, and parts of the cerebellum. Patients but not controls reported higher levels of anxiety and helplessness during the unresolved versus resolved memory condition.Conclusions. The activation of both, the amygdala and prefrontal areas, might reflect an increased effortful but insufficient attempt to control intensive emotions during the recall of unresolved life events in patients with BPD.
Review of: c-Myc suppresses p21WAF1/CIP1expression during oestrogen signalling and antioestrogen resistance in human breast cancer cells
Authors: McNeil C. M. , Musgrove E. A. 
Published: March 2006

Citation of original article:S. Mukherjee, S. E. Conrad.Journal of Biological Chemistry2005;280: 17616–17625.Abstract of the original article:Oestrogen rapidly induces expression of the proto-oncogene c-Myc. c-Myc is required for oestrogen-stimulated proliferation of breast cancer cells, and deregulated c-Myc expression has been implicated in antioestrogen resistance. In this report, we investigate the mechanism(s) by which c-Myc mediates oestrogen-stimulated proliferation and contributes to cell cycle progression in the presence of antioestrogen. The MCF-7 cell line is a model of oestrogen-dependent, antioestrogen-sensitive human breast cancer. Using stable MCF-7 derivatives with inducible c-Myc expression, we demonstrated that in antioestrogen-treated cells, the elevated mRNA and protein levels of p21WAF1/CIP1, a cell cycle inhibitor, decreased upon either c-Myc induction or oestrogen treatment. Expression of p21 blocked c-Myc-mediated cell cycle progression in the presence of antioestrogen, suggesting that the decrease in p21WAF1/CIP1is necessary for this process. Using RNA interference to suppress c-Myc expression, we further established that c-Myc is required for oestrogen-mediated decreases in p21WAF1/CIP1. Finally, we observed that neither c-Myc nor p21WAF1/CIP1is regulated by oestrogen or antioestrogen in an antioestrogen-resistant MCF-7 derivative. The p21 levels in the antioestrogen-resistant cells increased when c-Myc expression was suppressed, suggesting that loss of p21 regulation was a consequence of constitutive c-Myc expression. Together, these studies implicate p21WAF1/CIP1as an important target of c-Myc in breast cancer cells and provide a link between oestrogen, c-Myc, and the cell cycle machinery. They further suggest that aberrant c-Myc expression, which is frequently observed in human breast cancers, can contribute to antioestrogen resistance by altering p21WAF1/CIP1regulation.
Parallel deficits in linear growth and mental development in low-income Mexican infants in the second year of life
Authors: Fernald Lia C , Neufeld Lynnette M , Barton Lauren R , Schnaas Lourdes , Rivera Juan , Gertler Paul J 
Published: March 2006

AbstractObjectiveTo explore anthropometric indicators and mental development in very-low-income children in the second year of life.DesignCross-sectional survey.SettingLow-income areas (income <20th percentile) in semi-urban Mexico (defined as towns or cities with 2500–50 000 inhabitants).SubjectsEight hundred and ninety-six children aged 12.5–23.5 months surveyed from September to December 2001.MethodsQuestionnaire survey and anthropometric survey of households. Multivariate regression models evaluated differences across age in anthropometry (height-for-ageZ-score (HAZ) and weight-for-heightZ-score) and cognitive function (Mental Development Index (MDI) of the Bayley Scales of Infant Development) while controlling for socio-economic and parental characteristics.ResultsThere was a significant decline in HAZ and in age-adjusted MDI score across the second year of life. Although the children showed MDI scores close to the mean, normed US values at 13–14 months, the scores were significantly lower than expected in older children (P< 0.0001), even after controlling for socio-economic status and parental characteristics. At 13–14 months, only 3% of children received scores below 70 (less than minus two standard deviations), whereas by 19–20 months, almost 17% of children were performing below this level. No socio-economic or parental characteristics were significant predictors of HAZ or MDI.ConclusionsParallel deficits are evident in both height-for-age and cognitive functioning during the second year of life in low-income Mexican infants. The consistency of these growth and development findings further stresses the need for targeted interventions to reduce the vulnerability of low-income Mexican children very early in life.
Layers and spikes in non-homogeneous bistable reaction-diffusion equations
Authors: Ai Shangbing , Chen Xinfu , Hastings Stuart 
Published: March 2006

We study

ε
2

u
¨

=
f
(
u
,
x
)
=
A

u

(
1
−
u
)

(
ϕ
−
u
)

\varepsilon ^2\ddot {u}=f(u,x)=A\, u\, (1-u)\,(\phi -u)

, where

A
=
A
(
u
,
x
)
>
0

A=A(u,x)>0

,

ϕ
=
ϕ
(
x
)
∈
(
0
,
1
)

\phi =\phi (x)\in (0,1)

, and

ε
>
0

\varepsilon >0

is sufficiently small, on an interval

[
0
,
L
]

[0,L]

with boundary conditions

u
˙

=
0

\dot {u}=0

at

x
=
0
,
L

x=0,L

. All solutions with an

ε
\varepsilon

independent number of oscillations are analyzed. Existence of complicated patterns of layers and spikes is proved, and their Morse index is determined. It is observed that the results extend to

f
=
A
(
u
,
x
)

(
u
−

ϕ
−

)

(
u
−
ϕ
)

(
u
−

ϕ
+

)

f=A(u,x)\; (u-\phi _-)\,(u-\phi )\,(u-\phi _+)

with

ϕ
−

(
x
)
>
ϕ
(
x
)
>

ϕ
+

(
x
)

\phi _-(x)>\phi (x)>\phi _+(x)

and also to an infinite interval.