scholarly journals Helium Abundances in Gaseous Nebulae

1989 ◽  
Vol 131 ◽  
pp. 211-211 ◽  
Author(s):  
R.E.S. Clegg ◽  
J. P. Harrington
Keyword(s):  
Planetary Nebulae ◽  
H Ii Regions ◽  
Type I ◽  
Quantum Calculation ◽  
Recombination Line ◽  
Metastable Helium ◽  
Gaseous Nebulae ◽  
The Mean

New collision strengths, from a 19-state quantum calculation for He I, are used to derive revised He/H ratios in planetary nebulae (PN). Empirical formulae are given, for the correction of He I recombination line fluxes for collisional effects, and for the calculation of the population of metastable helium (He I 23S) in gaseous nebulae. The revised He abundances for PN, for four samples of published line fluxes, show a mean ratio He/H = 0.100 ±0.007 if nebulae with neutral He and Type I PN are excluded. The mean reduction due to collisional effects is only 10% for Galactic PN. It is shown that the hypothesis, that He/H should be independent of nebular temperature and density, is better satisfied when collisional effects are allowed for. The new He abundances indicate that there is very little He enrichment in Galactic PN of Types II, III, and IV, and that the enhancement of Type I PN in He over H II regions is reduced from earlier values by one third.

scholarly journals Collisional Excitation of the 10830 He I Line and the Population of the 23S He I State in Gaseous Nebulae

1989 ◽  
Vol 131 ◽  
pp. 212-212
Author(s):  
M. Peimbert ◽  
S. Torres-Peimbert
Keyword(s):  
Optical Depth ◽  
Planetary Nebulae ◽  
H Ii Regions ◽  
Type I ◽  
Line Intensities ◽  
Gaseous Nebulae ◽  
Radiative Transitions ◽  
Ngc 7027 ◽  
Ngc 7662 ◽  
Dust Absorption

From the study of the λλ5876, 7065 and 10830 He I line intensities in NGC 6572, NGC 6803, NGC 7009, NGC 7027, NGC 7662 and IC 418, it is found that the I(10830)/I(5876) ratio is weaker than expected. By considering estimates of the optical depth at λ10830 due to dust absorption and by determining the optical depth at λ10830 due to atomic absorption, it is argued that dust absorption of λ(10830) photons is not the cause for the low I(10830)/I(5876) ratios. By assuming that the 23S He0 state is depopulated only by radiative transitions to the 11S state and by triplet-singlet exchange collisions, it is found that its population is about a factor of two smaller than expected. This result is in agreement with a previous study of the λ3889, 4472, 5876, 6678 and 7065 line intensities in a group of thirteen Type I planetary nebulae. One of the main implications of the underpopulation of the 23S level is that the collisional effects in the N(He)/N(H) abundance ratios of planetary nebulae and 0-poor extragalactic H II regions are smaller than previously thought.

scholarly journals A Survey of Recombination-line Abundances in Planetary Nebulae and H II Regions

2003 ◽  
Vol 209 ◽  
pp. 383-384 ◽  
Author(s):  
Y. G. Tsamis ◽  
M. J. Barlow ◽  
X.-W. Liu ◽  
I. J. Danziger
Keyword(s):  
Planetary Nebulae ◽  
Magellanic Cloud ◽  
H Ii Regions ◽  
Recombination Line ◽  
Large Aperture

We have derived C, N and O abundances, relative to H, using optical recombination lines (ORLs), for a number of galactic planetary nebulae and for three Magellanic Cloud PNe (LMC N66, N141, SMC N87) and compared them with the corresponding abundances derived from collisionally-excited lines (CELs). Our goal was to investigate the fact that PNe ORL abundances are in most cases larger than those obtained from CELs. Our scanning, long-slit observations were combined with large-aperture IUE, IRAS and ISO data to yield integrated abundances for more than half of our target objects.

scholarly journals Planetary nebulae in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 299-306 ◽  
Author(s):  
M. A. Dopita
Keyword(s):  
Planetary Nebulae ◽  
Central Star ◽  
Magellanic Cloud ◽  
Expansion Velocity ◽  
H Ii Regions ◽  
Type I ◽  
Chemical Abundances ◽  
Processed Material ◽  
Density Radius ◽  
Central Stars

We present a simple two-wind model for the evolution of the Magellanic Cloud planetary nebulae (PN) which reproduces the observed density / radius / ionised mass relationships, and serves to define the geometrical relationship between the ionised nebula and the star. From self-consistent photoionisation modelling of 78 Magellanic Cloud PN, we have constructed the H-R Diagram for the central stars, and have derived both the chemical abundances and the nebular parameters. We find that the central stars have masses generally between 0.55 and 0.7 M⊙. Type I PN have more massive precursors, and show clear evidence for the Third dredge-up episode and for the dredge-up of ON processed material. The expansion velocity of the nebula is closely correlated with the position of the central star on the H-R Diagram, proving that the nebula undergoes continuous acceleration. Excluding Type I PN, the mean abundances derived for the LMC and the SMC agree with those derived from H II regions and evolved, radiative SNR.

scholarly journals METALLICITY GRADIENTS IN M31, M 33, NGC 300 AND THE MILKY WAY USING ABUNDANCES OF DIFFERENT ELEMENTS

2019 ◽  
Vol 55 (2) ◽  
pp. 255-271 ◽  
Author(s):  
Miriam Peña ◽  
Sheila N. Flores-Durán
Keyword(s):  
Milky Way ◽  
Planetary Nebulae ◽  
Extreme Case ◽  
H Ii Regions ◽  
Type I ◽  
Chemical Abundances ◽  
Homogeneous Sample ◽  
Radial Migration ◽  
Chemical Gradients ◽  
M 31

Metallicity gradients derived from planetary nebulae (PNe) using O, Ne, and Ar abundances are studied and compared to those from H ii regions in the galaxies M 31, M 33, NGC 300 and the Milky Way. Galactocentric radii and chemical abundances were collected from the literature, carefully selecting a homogeneous sample for each galaxy. Metallicity gradients shown by PNe are flatter than those of H ii regions in all cases. The extreme case is M 31 where PN abundances are not related to galactocentric distances and the gradients are consistent with zero. To analyze the evolution of gradients with time we build gradients for Peimbert Type I and non-Type I PNe finding that Type I PNe show steeper gradients than non-Type I PNe and more similar to the ones of H ii regions indicating that the chemical gradients might steepen with time. Alternatively, the flat gradients for old PNe show that radial migration could have an important role in the evolution of galaxies.

scholarly journals Abundances and nebular and central star masses for Magellanic Cloud planetary nebulae

1991 ◽  
Vol 148 ◽  
pp. 334-336 ◽  
Author(s):  
N. A. Walton ◽  
M. J. Barlow ◽  
D. J. Monk ◽  
R.E.S. Clegg
Keyword(s):  
Energy Balance ◽  
Planetary Nebulae ◽  
Central Star ◽  
Magellanic Clouds ◽  
Optical Data ◽  
Type I ◽  
Density Plot ◽  
Elemental Abundances ◽  
The Mean ◽  
Hydrogen Mass

We present the results of a spectroscopic study of planetary nebulae (PN) in the Magellanic Clouds. The optical survey of He, N, O, and Ne abundances by Monk et al. (1988) has been updated by higher S/N AAT optical data. In addition, carbon and other elemental abundances have been derived from the IUE spectra of 38 PN. Ionized nebular masses have been derived for 80 PN. The ionised mass versus nebular electron density plot shows that planetary nebulae become optically thin when their electron densities drop below 4500 cm--3. Below this density, the mean nebular hydrogen mass found for non-Type I PN is 0.22±0.08 M⊙. Using Zanstra and energy-balance methods, the mean central star mass found for 14 SMC and LMC PN is 0.59±0.02 M⊙.

Comparative Study of effectiveness of mobilization with movement (MWM) and End range mobilization (ERM) techniques in frozen shoulder

2018 ◽  
Vol 4 (4) ◽  
pp. 519-522
Author(s):  
Jeyakumar S ◽  
Jagatheesan Alagesan ◽  
T.S. Muthukumar
Keyword(s):  
Range Of Motion ◽  
Frozen Shoulder ◽  
Type I ◽  
Mean Values ◽  
Functional Activities ◽  
Group A ◽  
The Mean ◽  
Group B

Background: Frozen shoulder is disorder of the connective tissue that limits the normal Range of motion of the shoulder in diabetes, frozen shoulder is thought to be caused by changes to the collagen in the shoulder joint as a result of long term Hypoglycemia. Mobilization is a therapeutic movement of the joint. The goal is to restore normal joint motion and rhythm. The use of mobilization with movement for peripheral joints was developed by mulligan. This technique combines a sustained application of manual technique “gliding” force to the joint with concurrent physiologic motion of joint, either actively or passively. This study aims to find out the effects of mobilization with movement and end range mobilization in frozen shoulder in Type I diabetics. Materials and Methods: 30 subjects both male and female, suffering with shoulder pain and clinically diagnosed with frozen shoulder was recruited for the study and divided into two groups with 15 patients each based on convenient sampling method. Group A patients received mobilization with movement and Group B patients received end range mobilization for three weeks. The outcome measurements were SPADI, Functional hand to back scale, abduction range of motion using goniometer and VAS. Results: The mean values of all parameters showed significant differences in group A as compared to group B in terms of decreased pain, increased abduction range and other outcome measures. Conclusion: Based on the results it has been concluded that treating the type 1 diabetic patient with frozen shoulder, mobilization with movement exercise shows better results than end range mobilization in reducing pain and increase functional activities and mobility in frozen shoulder.

Radiological and clinical associations with scoliosis outcomes after posterior fossa decompression in patients with Chiari malformation and syrinx from the Park-Reeves Syringomyelia Research Consortium

2020 ◽  
Vol 26 (1) ◽  
pp. 53-59 ◽  
Author(s):  
Jennifer M. Strahle ◽  
Rukayat Taiwo ◽  
Christine Averill ◽  
James Torner ◽  
Jordan I. Gewirtz ◽  
...  
Keyword(s):  
Posterior Fossa ◽  
Chiari Malformation ◽  
Craniocervical Junction ◽  
Curve Progression ◽  
Posterior Fossa Decompression ◽  
Type I ◽  
Younger Age ◽  
Curve Magnitude ◽  
The Mean

OBJECTIVEIn patients with Chiari malformation type I (CM-I) and a syrinx who also have scoliosis, clinical and radiological predictors of curve regression after posterior fossa decompression are not well known. Prior reports indicate that age younger than 10 years and a curve magnitude < 35° are favorable predictors of curve regression following surgery. The aim of this study was to determine baseline radiological factors, including craniocervical junction alignment, that might predict curve stability or improvement after posterior fossa decompression.METHODSA large multicenter retrospective and prospective registry of pediatric patients with CM-I (tonsils ≥ 5 mm below the foramen magnum) and a syrinx (≥ 3 mm in width) was reviewed for clinical and radiological characteristics of CM-I, syrinx, and scoliosis (coronal curve ≥ 10°) in patients who underwent posterior fossa decompression and who also had follow-up imaging.RESULTSOf 825 patients with CM-I and a syrinx, 251 (30.4%) were noted to have scoliosis present at the time of diagnosis. Forty-one (16.3%) of these patients underwent posterior fossa decompression and had follow-up imaging to assess for scoliosis. Twenty-three patients (56%) were female, the mean age at time of CM-I decompression was 10.0 years, and the mean follow-up duration was 1.3 years. Nine patients (22%) had stable curves, 16 (39%) showed improvement (> 5°), and 16 (39%) displayed curve progression (> 5°) during the follow-up period. Younger age at the time of decompression was associated with improvement in curve magnitude; for those with curves of ≤ 35°, 17% of patients younger than 10 years of age had curve progression compared with 64% of those 10 years of age or older (p = 0.008). There was no difference by age for those with curves > 35°. Tonsil position, baseline syrinx dimensions, and change in syrinx size were not associated with the change in curve magnitude. There was no difference in progression after surgery in patients who were also treated with a brace compared to those who were not treated with a brace for scoliosis.CONCLUSIONSIn this cohort of patients with CM-I, a syrinx, and scoliosis, younger age at the time of decompression was associated with improvement in curve magnitude following surgery, especially in patients younger than 10 years of age with curves of ≤ 35°. Baseline tonsil position, syrinx dimensions, frontooccipital horn ratio, and craniocervical junction morphology were not associated with changes in curve magnitude after surgery.

scholarly journals Planetary Nebulae in M31: Abundances, and comparison with bright Planetary Nebulae in the LMC

1997 ◽  
Vol 180 ◽  
pp. 475-476
Author(s):  
M. G. Richer ◽  
G. Stasińska ◽  
M. L. McCall
Keyword(s):  
Planetary Nebula ◽  
Luminosity Function ◽  
Large Population ◽  
Wavelength Region ◽  
Planetary Nebulae ◽  
Surprising Result ◽  
Population Synthesis ◽  
Abundance Distribution ◽  
Wide Range ◽  
The Mean

We have obtained spectra of 28 planetary nebulae in the bulge of M31 using the MOS spectrograph at the Canada-France-Hawaii Telescope. Typically, we observed the [O II] λ3727 to He I λ5876 wavelength region at a resolution of approximately 1.6 å/pixel. For 19 of the 21 planetary nebulae whose [OIII]λ5007 luminosities are within 1 mag of the peak of the planetary nebula luminosity function, our oxygen abundances are based upon a measured [OIII]λ4363 intensity, so they are based upon a measured electron temperature. The oxygen abundances cover a wide range, 7.85 dex < 12 + log(O/H) < 9.09 dex, but the mean abundance is surprisingly low, 12 + log(O/H)–8.64 ± 0.32 dex, i.e., roughly half the solar value (Anders & Grevesse 1989). The distribution of oxygen abundances is shown in Figure 1, where the ordinate indicates the number of planetary nebulae with abundances within ±0.1 dex of any point on the x-axis. The dashed line indicates the mean abundance, and the dotted lines indicate the ±1 σ points. The shape of this abundance distribution seems to indicate that the bulge of M31 does not contain a large population of bright, oxygen-rich planetary nebulae. This is a surprising result, for various population synthesis studies (e.g., Bica et al. 1990) have found a mean stellar metallicity approximately 0.2 dex above solar. This 0.5 dex discrepancy leads one to question whether the mean stellar metallicity is as high as the population synthesis results indicate or if such metal-rich stars produce bright planetary nebulae at all. This could be a clue concerning the mechanism responsible for the variation in the number of bright planetary nebulae observed per unit luminosity in different galaxies (e.g., Hui et al. 1993).

scholarly journals Minimal Invasive Surgery for Gastroesophageal Reflux Disease and Hiatus Hernia—Our Experience: A Case Series with Review of Literature

2021 ◽  
Author(s):  
Rafique Umer Harvitkar ◽  
Abhijit Joshi
Keyword(s):  
Retrospective Study ◽  
Gastroesophageal Reflux Disease ◽  
Gastroesophageal Reflux ◽  
Operating Time ◽  
Type I ◽  
Type Ii ◽  
The Mean ◽  
Gerd Symptoms

Abstract Introduction Laparoscopic fundoplication (LF) has almost completely replaced the open procedure performed for gastroesophageal reflux disease (GERD) and hiatus hernia (HH). Several studies have suggested that long-term results with surgery for GERD are better than a medical line of management. In this retrospective study, we outline our experience with LF over 10 years. Also, we analyze the factors that would help us in better patient selection, thereby positively affecting the outcomes of surgery. Patients and Methods In this retrospective study, we identified 27 patients (14 females and 13 males) operated upon by a single surgeon from 2010 to 2020 at our institution. Out of these, 25 patients (12 females and 13 males) had GERD with type I HH and 2 (both females) had type II HH without GERD. The age range was 24 to 75 years. All patients had undergone oesophago-gastro-duodenoscopy (OGD scopy). A total of 25 patients had various degrees of esophagitis. Two patients had no esophagitis. These patients were analyzed for age, sex, symptoms, preoperative evaluation, exact procedure performed (Nissen’s vs. Toupet’s vs. cruroplasty + gastropexy), morbidity/mortality, and functional outcomes. They were also reviewed to examine the length of stay, length of procedure, complications, and recurrent symptoms on follow-up. Symptoms were assessed objectively with a score for six classical GERD symptoms preoperatively and on follow-up at 1-, 4- and 6-weeks postsurgery. Further evaluation was performed after 6 months and then annually for 2 years. Results 14 females (53%) and 13 males (48%) with a diagnosis of GERD (with type I HH) and type II HH were operated upon. The mean age was 46 years (24–75 years) and the mean body mass index (BMI) was 27 (18–32). The range of duration of the preoperative symptoms was 6 months to 2 years. The average operating time dropped from 130 minutes for the first 12 cases to 90 minutes for the last 15 cases. The mean hospital stay was 3 days (range: 2–4 days). In the immediate postoperative period, 72% (n = 18) of the patients reported improvement in the GERD symptoms, while 2 (8%) patients described heartburn (grade I, mild, daily) and 1 (4%) patient described bloating (grade I, daily). A total of 5 patients (20%) reported mild dysphagia to solids in the first 2 postoperative weeks. These symptoms settled down after 2 to 5 weeks of postoperative proton-pump inhibitor (PPI) therapy and by adjusting consistency of oral feeds. There was no conversion to open, and we observed no perioperative mortality. There were no patients who underwent redo surgeries in the series. Conclusion LF is a safe and highly effective procedure for a patient with symptoms of GERD, and it gives long-term relief from the symptoms. Stringent selection criteria are necessary to optimize the results of surgery. Experience is associated with a significant reduction of operating time.

Split spinal cord malformations in children

1998 ◽  
Vol 88 (1) ◽  
pp. 57-65 ◽  
Author(s):  
Yusuf Ersşahin ◽  
Saffet Mutluer ◽  
Sevgül Kocaman ◽  
Eren Demirtasş
Keyword(s):  
Spinal Cord ◽  
Neurological Deficits ◽  
Single Type ◽  
Type I ◽  
Type Ii ◽  
Content Type ◽  
Spinal Lesion ◽  
The Mean ◽  
Fine Print

Object. The authors reviewed and analyzed information on 74 patients with split spinal cord malformations (SSCMs) treated between January 1, 1980 and December 31, 1996 at their institution with the aim of defining and classifying the malformations according to the method of Pang, et al. Methods. Computerized tomography myelography was superior to other radiological tools in defining the type of SSCM. There were 46 girls (62%) and 28 boys (38%) ranging in age from less than 1 day to 12 years (mean 33.08 months). The mean age (43.2 months) of the patients who exhibited neurological deficits and orthopedic deformities was significantly older than those (8.2 months) without deficits (p = 0.003). Fifty-two patients had a single Type I and 18 patients a single Type II SSCM; four patients had composite SSCMs. Sixty-two patients had at least one associated spinal lesion that could lead to spinal cord tethering. After surgery, the majority of the patients remained stable and clinical improvement was observed in 18 patients. Conclusions. The classification of SSCMs proposed by Pang, et al., will eliminate the current chaos in terminology. In all SSCMs, either a rigid or a fibrous septum was found to transfix the spinal cord. There was at least one unrelated lesion that caused tethering of the spinal cord in 85% of the patients. The risk of neurological deficits resulting from SSCMs increases with the age of the patient; therefore, all patients should be surgically treated when diagnosed, especially before the development of orthopedic and neurological manifestations.

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