206 research outputs found
Solar and heliospheric sources of suprathermal and energetic particle populations
No full textObjectives and some preliminary findings of an ongoing international team project carried out at ISSI, Bern will be presented. Suprathermal and energetic particle
s in interplanetary space have a multitude of origins,
i.e. acceleration and propagation hi stories. Solar flares, coronal mass ejections (CMEs), co-rotating interaction regions (CIRs), the heliospheric termination shock, planetary bow shocks and magnetospheres have all been recognized as energetic particle sources. Less energetic (suprathermal) particles of solar origin and pick-up ions have also a vital role both in their own right and as seeds of energetic particles accelerated in interplanetary disturbances. The relative contributions of various particle populations vary with energy and with the phase of the solar cycle. Particular attention will be given in our project to quiet periods and to large events. While quiet-time fluxes are expected to shed light on some
base-line features of coronal and interplanetary acceleration processes, relatively large events dominate bot
h the long-term fluence levels and the statistical properties of cumulative fluence plots. The importance of energetic and suprathermal particles that mostly cannot escape into interplanetary space, but contribute to co
ronal heating and possibly also to solar wind composition, will also be discussed.
B. Sripathi Acharya, Sunil Gupta, P. Jagadeesan, Atul Jain, S. Karthikeyan, Samuel Morris, and Suresh Tonwa
Voiding dysfunction - A review
No full textIn a child who is toilet trained the sudden onset of daytime wetting with frequency or urgency is alarming to the parents. Initially this subject was subdivided into a number of descriptive clinical conditions which led to a lot of confusion in recognition and management. Subsequently, the term elimination dysfunction was coined by Stephen Koff to emphasise the association between recurrent urinary infection, wetting, constipation and bladder overactivity. From a urodynamic point of view, in voiding dysfunction, there is either detrusor overactivity during bladder filling or dyssynergic action between the detrusor and the external sphincter during voiding. Identifying a given condition as a ′filling phase dysfunction′ or ′voiding phase dysfunction′ helps to provide appropriate therapy. Objective clinical criteria should be used to define voiding dysfunction. These include bladder wall thickening, large capacity bladder and infrequent voiding, bladder trabeculation and spinning top deformity of the urethra and a clinically demonstrated Vincent′s curtsy. The recognition and treatment of constipation is central to the adequate treatment of voiding dysfunction. Transcutaneous electric nerve stimuation for the treatment of detrusor overactivity, biofeedback with uroflow EMG to correct dyssynergic voiding, and behavioral therapy all serve to correct voiding dysfunction in its early stages. In established neurogenic bladder disease the use of Botulinum Toxin A injections into the detrusor or the external sphincter may help in restoring continence especially in those refractory to drug therapy. However in those children in whom the upper tracts are threatened, augmentation of the bladder may still be needed
Dental implants: A boon to dentistry
No full textThe development and use of implants is one of the biggest advances in dentistry in the last few decades. It has helped to give many solutions to tooth loss as well as maxillo facial prosthetics. This article traces the history and evolution of dental implants
A study on the low-latitude daytime E region plasma irregularities using coordinated VHF radar, rocket-borne, and ionosonde observations
No full text[1] In this paper we study the off-electrojet low-latitude daytime E region plasma irregularities using first multi-instrument observations in India made during July 2004 by the MST radar from Gadanki (13.5°N, 79.2°E, magnetic latitude 6.4°N), Langmuir probe on board the RH-300 Mk II rocket, and ionosonde from Sriharikota (13.6°N, 80.2°E, magnetic latitude 6.4°N). Radar echoes were confined to altitudes below 105 km and were observed in the form of a descending echoing layer with the descent rate of 1 km/h. Virtual height of the E layer, as observed by ionosonde, shows identical descending behavior. A detailed analysis based on the radar and ionosonde observations shows that the radar echoes are related to the range spread in the ionogram. Rocket observations made on 23 July 2004 revealed weak plasma irregularities with scale sizes more than 100 m and no noticeable irregularity at shorter scales. The spectral slope of the irregularities observed by the rocket probe is found to be À4 for scales in between 1 km and 100 m. During the rocket launch, radar did not detect any echo conforming that the small-scale irregularities were not present. Examination of concurrent observations of neutral wind made by TIMED Doppler interferometry suggests that zonal wind plays a crucial role in forming electron density layers, which become unstable via the gradient drift instability with background electric field or/and zonal neutral wind generating low-latitude E region plasma irregularities. Citation: Patra, A. K., N. Venkateswara Rao, D. V. Phanikumar, H. Chandra, U. Das, H. S. S. Sinha, T. K. Pant, and S. Sripathi (2009), A study on the low-latitude daytime E region plasma irregularities using coordinated VHF radar, rocket-borne, and ionosonde observations
Rigid ureteroscopy in children: Our experience
No full textAim: To report our experience of Pediatric ureterorenoscopy for ureteric calculi from two tertiary Pediatric urology centers at Apollo Children′s Hospital, Chennai and Indraprastha Apollo Hospital, New Delhi. Material and methods: All children who presented with symptomatic ureteric stones greater than 6 mm were entered into the study. All children less than 12 months and more than 18 years of age and those who underwent ureterorenoscopy for indications other than the stones were excluded from the study. The children were managed on a fixed investigative and treatment protocol. The data from the Apollo Hospital New Delhi and Apollo Children′s Hospital Chennai was analysed. Results: There were a total of thirty eight children, twenty in Chennai and eighteen in the New Delhi study. The mean age was 10.4 years and 8.5 years and the youngest child was14 months and 24 months in the Chennai and New Delhi group respectively. There was one conversion to open surgery in either group. Pneumatic lithotripter was used in majority of cases and holmium laser in select children. Conclusion: This is the largest Indian series of ureterorenoscopy for ureteric calculi in children. This study over nearly a decade confirms the safety and efficacy of this technique even in young children. In children less than five years, prestenting and delayed ureterorenoscopy allows safe endoscopic treatment of ureteric calculi
COSMIC observations of ionospheric density profiles over Indian region: Ionospheric conditions during extremely low solar activity period
No full text98-109In the present paper, for the first time, an attempt has been made to study
the seasonal, altitudinal, diurnal and latitudinal variation of low latitude
electron density obtained using COSMIC radio occultation (RO) measurements over
Indian longitudes during the deep solar minimum year 2008. The seasonal
variation shows enhanced electron densities at vernal and autumn equinoxes
compared to winter and summer seasons. The observations also suggest a shift in
the time and altitude at which the peak of the electron density occurs in
different seasons. An important finding is that there exists an equinoctial
asymmetry in the electron density with respect to altitude and latitude, where
the electron density is higher at vernal equinox compared to autumn equinox.
The latitudinal and seasonal variation of peak electron density (NmF2)
during 10:00-14:00 hrs LT indicate enhanced equatorial ionization anomaly (EIA)
on either side of the magnetic equator at both vernal and autumn equinoxes
compared to the other seasons. Seasonal variation of equatorial electrojet
(EEJ) strength obtained from geomagnetic H-field variations also shows strong
EEJ at vernal and autumn equinoxes indicating that EEJ strength indeed partly controls
the EIA development. Further, the results indicate that NmF2
over the northern EIA crest region is correlated well with solar flux
Coding and cooperation in multi-user multi-antenna communication systems
No full textThe utility of multi-antenna transceivers in single-user, point-to-point links is well understood. With multiple antennas on both ends of a point-to-point link, spectral efficiency may be improved by spatial multiplexing, and link reliability may be improved by utilizing spatial diversity. Similar benefits also apply to multi-antenna systems in a multi-user environment. However, the conditions under which the benefits may be obtained and the techniques to achieve them differ significantly from the single-user environment. In this dissertation, multi-antenna techniques for three canonical multi-user systems, namely, broadcast, multiple-access, and cooperative are proposed and analyzed. Firstly, a technique for optimizing linear zero-forcing precoders for broadcast channels is proposed. A computationally efficient algorithm based on (Gram-Schmidt) QR-factorization and QR-updates is then proposed to implement this optimization technique. The proposed technique is utilized to identify optimal subspaces for communicating at low data-rates over the multi-antenna broadcast channel. The technique is then extended to high-data-rate communication. A nonlinear precoder based on sequential Tomlinson-Harashima preceding is then developed. The performance of the proposed precoders in terms of uncoded bit-error rates and coded bit-error rates with turbo codes is then evaluated, and their merit is established. The application of these techniques to multi-access channels is then discussed. Next, a scaling law for achievable throughput in coherent ad-hoc multi-input multi-output (MIMO) networks is established and its relevance to cellular networks is discussed. Finally, the concept of efficient co-operative diversity systems is introduced in the cellular context, and both coherent and non-coherent relaying schemes are introduced and analyzed
Voiding dysfunction - A review
No full textIn a child who is toilet trained the sudden onset of daytime wetting
with frequency or urgency is alarming to the parents. Initially this
subject was subdivided into a number of descriptive clinical conditions
which led to a lot of confusion in recognition and management.
Subsequently, the term elimination dysfunction was coined by Stephen
Koff to emphasise the association between recurrent urinary infection,
wetting, constipation and bladder overactivity. From a urodynamic point
of view, in voiding dysfunction, there is either detrusor overactivity
during bladder filling or dyssynergic action between the detrusor and
the external sphincter during voiding. Identifying a given condition as
a ′filling phase dysfunction′ or ′voiding phase
dysfunction′ helps to provide appropriate therapy. Objective
clinical criteria should be used to define voiding dysfunction. These
include bladder wall thickening, large capacity bladder and infrequent
voiding, bladder trabeculation and spinning top deformity of the
urethra and a clinically demonstrated Vincent′s curtsy. The
recognition and treatment of constipation is central to the adequate
treatment of voiding dysfunction. Transcutaneous electric nerve
stimuation for the treatment of detrusor overactivity, biofeedback with
uroflow EMG to correct dyssynergic voiding, and behavioral therapy all
serve to correct voiding dysfunction in its early stages. In
established neurogenic bladder disease the use of Botulinum Toxin A
injections into the detrusor or the external sphincter may help in
restoring continence especially in those refractory to drug therapy.
However in those children in whom the upper tracts are threatened,
augmentation of the bladder may still be needed
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