bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mesoscale Simulation of the Structure of Star Acrylated Poly(ethylene glycol-co-lactide) Hydrogels
Authors: Moeinzadeh Seyed Sina , Jabbari Esmaiel 
Published: January 2012

ABSTRACTIn this work the microstructures of star acrylated poly(ethylene glycol-co-lactide) (SPELA) with different LA:EG ratios in the aqueous solution have been simulated via Dissipative Particle Dynamics (DPD) approach at the mesoscale. The system components were coarse-grained into different beads (set of atoms) which moved according to the Newton’s equations of motion integrated via a modified Velocity-Verlet algorithm. The force acting on each bead, in a specific cutoff distance (rc), was divided into a conservative force (FC), random force (FR), dissipative force (FD), bond force (FS) and bond angle force (FE). The repulsion parameters of the conservative force (αij) were calculated from the solubility parameter of the beads, each of which were extracted from an atomistic molecular dynamics simulation (MD). Simulations showed the formation of micelles with lactide and acrylate beads occupied the core and hydrophilic ethylene oxide segments extending through the water to form the corona. The micelles showed an increasing trend in size and decreasing trend in number density with increase in LA:EG ratio. Results showed that the acrylate density decreased from the center of the micelles to the core surface although the overall amount of acrylates increased due to the increase in volume. Furthermore, the running integration number of acrylate-water beads showed decreasing accessibility of acrylates to water with increasing PLA volume fraction.
3D Printing Fumarate Based Polymers
Authors: Cicotte Kirsten N. , Hedberg-Dirk Elizabeth L. , Dirk Shawn M. 
Published: January 2012

ABSTRACTRecently, an inexpensive 3D lithography technique was developed by Professor Nicholas Fang at the University of Illinois where a projector is used in combination with a Microsoft® PowerPoint presentation to expose the liquid negative-tone photoresist 1,6-hexanediol diacrylate in a layer-by-layer fashion. Where Professor Fang initially used this method as a teaching tool, we have used the inexpensive 3D printing technique to create 3D structures of fumarate based polymers. This class of polymers are liquids at room temperature which makes them ideal for the projector based lithography technique when used in combination with the photoinitiator bisphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO). Furthermore, the fumarate based materials are biocompatible and are suitable candidates for tissue engineering applications.
Array nonrecursiveness and relative recursive enumerability
Authors: Cai Mingzhong 
Published: January 2012

AbstractIn this paper we prove that a degreeais array nonrecursive (ANR) if and only if every degreeb ≥ ais r.e. in and strictly above another degree (RRE). This result will answer some questions in [ASDWY]. We also deduce an interesting corollary that everyn-REAdegree has a strong minimal cover if and only if it is array recursive.
Thorn-forking in continuous logic
Authors: Ealy Clifton , Goldbring Isaac 
Published: January 2012

AbstractWe study thorn forking and rosiness in the context of continuous logic. We prove that the Urysohn sphere is rosy (with respect to finitary imaginaries), providing the first example of an essentially continuous unstable theory with a nice notion of independence. In the process, we show that a real rosy theory which has weak elimination of finitary imaginaries is rosy with respect to finitary imaginaries, a fact which is new even for discrete first-order real rosy theories.
The tree property at ℵω+1
Authors: Sinapova Dima 
Published: January 2012

AbstractWe show that givenωmany supercompact cardinals, there is a generic extension in which there are no Aronszajn trees at ℵω+1·This is an improvement of the large cardinal assumptions. The previous hypothesis was a huge cardinal andωmany supercompact cardinals above it, in Magidor–Shelah [7].
An incomplete set of shortest descriptions
Authors: Stephan Frank , Teutsch Jason 
Published: January 2012

AbstractThe truth-table degree of the set of shortest programs remains an outstanding problem in recursion theory. We examine two related sets, the set of shortest descriptions and the set of domain-random strings, and show that the truth-table degrees of these sets depend on the underlying acceptable numbering. We achieve some additional properties for the truth-table incomplete versions of these sets, namely retraceability and approximability. We give priority-free constructions of bounded truth-table chains and bounded truth-table antichains inside the truth-table complete degree by identifying an acceptable set of domain-random strings within each degree.
The complexity of squares in the group of isometries of the Baire space
Authors: Hill Aaron 
Published: January 2012

AbstractWe prove that in the Polish group of isometries of the Baire space the collection of n-th powers is non-Borel. We also prove that in the Polish space of trees on ℕ the collection of trees that have an automorphism under which every node has order exactly n is non-Borel.
Lack of causal association between spontaneous intracranial hypotension and cranial cerebrospinal fluid leaks
Authors: Schievink Wouter I. , Schwartz Marc S. , Maya M. Marcel , Moser Franklin G. , Rozen Todd D. 
Published: January 2012

Object
Spontaneous intracranial hypotension is an important cause of headaches and an underlying spinal CSF leak can be demonstrated in most patients. Whether CSF leaks at the level of the skull base can cause spontaneous intracranial hypotension remains a matter of controversy. The authors' aim was to examine the frequency of skull base CSF leaks as the cause of spontaneous intracranial hypotension.

Methods
Demographic, clinical, and radiological data were collected from a consecutive group of patients evaluated for spontaneous intracranial hypotension during a 9-year period.

Results
Among 273 patients who met the diagnostic criteria for spontaneous intracranial hypotension and 42 who did not, not a single instance of CSF leak at the skull base was encountered. Clear nasal drainage was reported by 41 patients, but a diagnosis of CSF rhinorrhea could not be established. Four patients underwent exploratory surgery for presumed CSF rhinorrhea. In addition, the authors treated 3 patients who had a postoperative CSF leak at the skull base following the resection of a cerebellopontine angle tumor and developed orthostatic headaches; spinal imaging, however, demonstrated the presence of a spinal source of CSF leakage in all 3 patients.

Conclusions
There is no evidence for an association between spontaneous intracranial hypotension and CSF leaks at the level of the skull base. Moreover, the authors' study suggests that a spinal source for CSF leakage should even be suspected in patients with orthostatic headaches who have a documented skull base CSF leak.
Surgical treatment of patients with vestibular schwannomas after failed previous radiosurgery
Authors: Gerganov Venelin M. , Giordano Mario , Samii Amir , Samii Madjid 
Published: January 2012

Object
An increasing number of patients with vestibular schwannomas (VSs) are being treated with radiosurgery. Treatment failure or secondary regrowth after radiosurgery, however, has been observed in 2%–9% of patients. In large tumors that compress the brainstem and in patients who experience rapid neurological deterioration, surgical removal is the only reasonable management option.

Methods
The authors evaluated the relevance of previous radiosurgery for the outcome of surgery in a series of 28 patients with VS. The cohort was further subdivided into Group A (radiosurgery prior to surgery) and Group B (partial tumor removal followed by radiosurgery prior to current surgery). The functional and general outcomes in these 2 groups were compared with those in a control group (no previous treatment, matched characteristics).

Results
There were 15 patients in Group A, 13 in Group B, and 30 in the control group. The indications for surgery were sustained tumor enlargement and progression of neurological symptoms in 12 patients, sustained tumor enlargement in 15 patients, and worsening of neurological symptoms without evidence of tumor growth in 1 patient. Total tumor removal was achieved in all patients in Groups A and B and in 96.7% of those in the control group. There were no deaths in any group. Although no significant differences in the neurological morbidity or complication rates after surgery were noted, the risk of new cranial nerve deficits and CSF leakage was highest in patients in Group B. Patients who underwent previous radiosurgical treatment (Groups A and B) tended to be at higher risk of developing postoperative hematomas in the tumor bed or cerebellum. The rate of facial nerve anatomical preservation was highest in those patients who were not treated previously (93.3%) and decreased to 86.7% in the patients in Group A and to 61.5% in those in Group B. Facial nerve function at follow-up was found to correlate to the previous treatment; excellent or good function was seen in 87% of the patients from the control group, 78% of those in Group A, and 68% of those in Group B.

Conclusions
Complete microsurgical removal of VSs after failed radiosurgery is possible with an acceptable morbidity rate. The functional outcome, however, tends to be worse than in nontreated patients. Surgery after previous partial tumor removal and radiosurgery is most challenging and related to worse outcome.
On Pyrheliometric Measurements
Authors: Angström Anders 
Published: January 2012

Pyrheliometric measurements are now introduced in the meteorological practice to an extent which makes a condensed survey over the present status desirable.
In the following I have combined the main content of the survey on the pyrheliometric scales, given by the International Radiation Commissions, with a description of the present modernized type of the Ångström Pyrheliometer. I have added a critical examination of its function and the sources of error which ought to be avoided at its operation. A detailed survey of its construction seems justified by the fact that it is the only standard instrument at present available in the market, where institutes can easily determine its physical constants, thus controlling the basis for absolute measurements of solar radiation. I have added an Annex containing a simple theory of the “edge effect” in the pyrheliometer. The main content of the annex coincides practically with the theory I gave already in 1914, but I repeat it here with some minor corrections together with a discussion of the factors influencing the effect and also of the results of practical experiments.
The important result is derived, that the edge correction is to some extent dependent on the internal convection within the pyrheliometer, and may from this reason vary between about 1.3 and 3.8 percent of the measured radiation. In the new constructions, now available in Sweden, this error is eliminated.
Some Comments on the Numerical Integration of the Vorticity Equation and Related Equations
Authors: Benton George S. 
Published: January 2012

It is shown that if the streamfunction is specified over an Eulerian region R (x, y) at t=0, and on the boundaries of R (x, y) at t > 0, a solution of the vorticity equation which satisfies certain conditions of continuity will be unique. If vorticity is also specified at the inflow boundary, such a solution is excluded. In the latter case, an internal discontinuity propagates into the region along a material surface, and in principle solutions should be obtained separately for each sub-region and “matched” kinematically and dynamically at the interface. The associated analytical or numerical problems are prohibitive.
The problem of obtaining stable methods of numerical integration, specifying only the stream function on the boundary, is considered. Numerical integrations of a non-linear first order differential equation indicate that such stable methods may exist, in contradiction to linear theory.
The integration of the vorticity and associated equations for the first time-step is also considered. A method is presented which is not only simple to apply, but also maintains the same accuracy as succeeding time-steps for which centered difference techniques are used.
Study of Cosmic Ray Produced Short-Lived P<sup>32</sup>, P<sup>33</sup>, Be<sup>7</sup>, and S<sup>35</sup>&nbsp;in Tropical Latitudes
Authors: Goel P. S. , Narasappaya N. , Prabhakara C. , Thor Rama , Zutshi P. K. 
Published: January 2012

The fall-out rate of four short-lived isotopes P32, P33, Be7 and S35, produced in the collisions of cosmic ray particles with air nuclei, has been measured at a number of stations in India and compared with the calculated rate of production. In the case of Be7, the agreement between the calculated and measured values is good. The fall-out rates of P32 and P33 are not inconsistent with the calculated values; that of S35, however, is about five times higher than expected.
The absolute concentrations of an individual isotope in various rain falls have been found to vary by more than a factor of forty; relative concentrations of the different isotopes, however, stayed within fairly narrow limits. The ratio of the concentration of the isotope Be7 to that of the isotope P32 in individual rain samples has been used to find out the periods for which various air masses had been irradiated in the interval between two successive precipitations. The mean period of irradiation is found to be about thirty-five days.
Our results are consistent with the view that, in these tropical latitudes, intrusions of stratospheric air into the troposphere are either rare or weak in intensity.
The method seems capable of further development as a tool for studying meteorological problems.
The Evaporation-Precipitation Cycle of the Trades
Authors: Kraus E. B. 
Published: January 2012

The area distribution of surface wind strengths between 30° S and 30° N is expressed as a function of the median velocity, on the basis of climatological data. This is used to obtain estimates of evaporation and energy dissipation over the same area.
The main energy supply of the trade circulation is due to condensation in the equatorial trough. It depends partly on evaporation into the trade winds at some earlier time. A study of the energy balance shows that this may lead to oscillations with a period of about 3 weeks; corresponding to the mode of the time which elapses between the evaporation and the precipitation of the same vapour molecules.
Disturbances or fluctuations in the direct meridional circulation of the sub-tropics may be initiated by changes in the infra-red cooling rate and by changes in the height of the tropopause. It is suggested tentatively that this could be caused by changes in the ozone distribution above the tropical tropopause.
The Daily Variation of the Cosmic Ray Nucleonic Component at Murchison Bay and Uppsala
Authors: Sandström Arne Eld , Dyring Eric , Lindgren Stig 
Published: January 2012

In both places the monitors were of the standard pattern with 12 proportional counters filled with 97 per cent enriched B10F8. The first and second harmonics of the mean daily variation have been determined both for yearly periods and for each sun rotation period. Vector sum diagrams for the first harmonics in the latter case are given covering the intervals 31 Aug. 1956 to 15 Aug. 1959 for Uppsala and 13 Sept. 1957 to 29 April 1959 for Murchison Bay. In some instances a considerable phase shift has taken place from one sequence of sun rotation periods to another. These phase shifts were not contemporary at the two stations. The first harmonic of the 12-month means displays a high degree of constancy with only a small secular phase shift. The amplitudes of the second harmonics are very small. Conditions are especially favourable concerning the deviation in the earth’s magnetic field of the particles registered by the Murchison Bay monitor. Accordingly it has been possible to determine the direction of the anisotropy with a fairly good accuracy. The Murchison Bay records do not show any prominent phase shift with the Kp index. Concerning Uppsala, days with [Kp]max ≤ 1+ have a later time of maximum than other days. The influence of single days with an abnormal daily variation is discussed.
Measurements of the Water Vapour, Tritium and Carbon-14 Content of the Middle Stratosphere over Southern England
Authors: Brown F. , Goldsmiths P. , Green H. F. , Holt A. , Parham A. G. 
Published: January 2012

Measurements of the water vapour, tritium and carbon-14 content of the stratosphere at heights of between 80,000 and 100,00 feet, made over England during the years 1956 to 1960, are described.
The tritium and carbon-14 concentrations are greater than those expected from natural production due to the cosmic radiation. The bulk of these two isotopes, at present in the stratosphere, has been injected there during the course of thermonuclear explosions.
Mass spectrometric analyses show that the deuterium/hydrogen ratio of the water and the carbon-13/carbon-12 and oxygen-16/oxygen-18 ratios of the carbon dioxide collected at these heights were the same, within the accuracy of measurement, as those for samples collected near the ground.
The concentration of tritium at the heights of the measurements has not fallen since the termination of thermonuclear weapon testing in autumn 1958. There is poor correlation between the tritium concentration at 90,000 feet and that of particulate caesium-137 at 47,000 feet measured over the sampling period. The humidity above 80,000 feet is found to be greater than that in the lower stratosphere.
It is concluded from these humidity and tritium results that the large scale meridional circulation in the stratosphere, first postulated by Brewer and Dobson, does not reach heights of 90,000 feet over temperate latitudes.
Note on the Propagation of Baroclinic Waves in a Zonal Ocean Current
Authors: Welander Pierre 
Published: January 2012

In a zonal ocean current one sees Stationary or slowly moving baroclinic waves, with a wavelength of 1,000 km or more. These waves may be equivalent to a type of very long waves studied earlier in the atmospheric case. The wave speed is independent of the wave number but depends on the speed of the basic current, the stratification etc. For the case of a zonal current with exponential vertical profile, stationary waves are found for an eastward current. The wave perturbation normally decays downward in an exponential way. The parameter that decides the nature of the waves is λ = β/f2 ΔAp0/U0 where U0 is the amplitude of the basic current, ΔA the vertical variation of the specific volume, p0 the scale pressure (the pressure variation that corresponds to the scale depth of the basic current), and f the Coriolis parameter. For a westward current travelling neutral waves exist but only for special values of λ that are not normally expected in the oceans.
On the Geostrophic Flow at the Surface of the Pacific Ocean with Respect to the 1,000-decibar Surface
Authors: Reid, Jr. Joseph L. 
Published: January 2012

The geopotential anomaly at the surface of the Pacific Ocean with respect to the 1,000-decibar surface is computed. Horizontal variations in geopotential at greater depth are shown to be smaller and are neglected. The geostrophic flow at the sea surface with respect to the 1,000-decibar surface is shown to agree in general with the averages of currents estimated from the set and drift of vessels and tabulated in various atlases. The major gyres of the ocean are clearly shown and one new feature, a South Equatorial Countercurrent, is revealed in the western Pacific.
Since there is meridional flow in the ocean, the flow is not entirely geostrophic and the contours of geopotential anomaly may lie at some angle to the streamlines. This is most evident where the contours intersect the coast and cross the equator. A qualitative consideration of wind stress indicates that where wind and current are in the same direction geopotential anomaly will rise along a streamline and where they are opposed geopotential anomaly will decrease along a streamline. This effect can at least qualitatively account for the rise of geopotential anomaly to the west in the region of the trades and toward the east in the northern hemisphere westerlies.
On baroclinic instability in filtered and non-filtered numerical prediction models
Authors: Wiin-Nielsen Aksel 
Published: January 2012

The criterion for baroclinic instability in a two level model of the large-scale motion in the atmosphere is computed and compared for the following cases: (1) A quasigeostrophic model with constant static stability. (2) A quasi-geostrophic model with a horizontal variation of static stability. (3) A primitive equation model with constant static stability. (4) A primitive equation model with horizontal variation of static stability.
It is found that the models containiig a horizontal variation of the static stability have a maximum instability at shorter wavelengths than the models with constant static Stability; that only small differences are observed in the amplification rate of baroclinic disturbances in models with the aame variation of static stability but with different basic equations 88 long as the variation of the meteorological parameters are in the observed range; but that large differences in the amplification rate occur when the Richardson number is small, i.e. for smell mean static stabilities and/or large vertical wind shears.
The structure of the baroclinically unstable disturbances are computed and compared for the four models mentioned above. The variation of the ageostrophic wind and the static stability through the wave is of special importance. It tuns out that the maximum ageostrophic wind at the upper level is about 15 % of the maximum wind, while the corresponding number at the lower level is 20 %. The distribution of the ageostrophic wind at the upper level is such that the wind is supergeostrophic around the ridge in the geopotential with a maximum close to the maximum geopotential and subgeostrophic around the trough in the geopotential. The distribution of static stability in the developing baroclinic wave is such that the air becomes more stable than the average between the ridge and trough (looking downstream), but more unstable between the trough and the ridge.
Currents induced by tides and gravity waves
Authors: Hunt J. N. , Johns B. 
Published: January 2012

Two-dimensional oscillatory potential flow was shown by Rayleigh and Schlichting to give rise to a steady second-order streaming at the outer edge of a laminar boundary layer. Their method is here extended to a three-dimensional Oscillatory flow which may be represented at a plane boundary by two harmonic oscillations (U, V) of frequency σ/2π in perpendicular horizontal directions.
The resulting second-order mean velocity components are interpreted in terms of bottom currents induced by tidal motion in shallow sew, or by doubly modulated gravity waves. These currents depend critically on the relative magnitudes of U, V and f/σ, where f is the Coriolis parameter.
It is suggested that on the tidal scale, such currents may contribute to the circulation within the North Sea, while on the gravity wave scale they contribute to the formation of offshore sandbars around the coasts.