Experimental and numerical simulation of a TPC like set up for the measurement of ion backflow

Ion backflow is one of the effects limiting the operation of a gaseous detector at high flux, by giving rise to space charge which perturbs the electric field. The natural ability of bulk Micromegas to suppress ion feedback is very effective and can help the TPC drift volume to remain relatively free of space charge build-up. An efficient and precise measurement of the backflow fraction is necessary to cope up with the track distortion due to the space charge effect. In a subtle but significant modification of the usual approach, we have made use of two drift meshes in order to measure the ion backflow fraction for bulk Micromegas detector. This helps to truly represent the backflow fraction for a TPC. Moreover, attempt is taken to optimize the field configuration between the drift meshes. In conjunction with the experimental measurement, Garfield simulation framework has been used to simulate the related physics processes numerically

Repeating Spatial-Temporal Motifs of CA3 Activity Dependent on Engineered Inputs from Dentate Gyrus Neurons in Live Hippocampal Networks.

Anatomical and behavioral studies, and in vivo and slice electrophysiology of the hippocampus suggest specific functions of the dentate gyrus (DG) and the CA3 subregions, but the underlying activity dynamics and repeatability of information processing remains poorly understood. To approach this problem, we engineered separate living networks of the DG and CA3 neurons that develop connections through 51 tunnels for axonal communication. Growing these networks on top of an electrode array enabled us to determine whether the subregion dynamics were separable and repeatable. We found spontaneous development of polarized propagation of 80% of the activity in the native direction from DG to CA3 and different spike and burst dynamics for these subregions. Spatial-temporal differences emerged when the relationships of target CA3 activity were categorized with to the number and timing of inputs from the apposing network. Compared to times of CA3 activity when there was no recorded tunnel input, DG input led to CA3 activity bursts that were 7× more frequent, increased in amplitude and extended in temporal envelope. Logistic regression indicated that a high number of tunnel inputs predict CA3 activity with 90% sensitivity and 70% specificity. Compared to no tunnel input, patterns of >80% tunnel inputs from DG specified different patterns of first-to-fire neurons in the CA3 target well. Clustering dendrograms revealed repeating motifs of three or more patterns at up to 17 sites in CA3 that were importantly associated with specific spatial-temporal patterns of tunnel activity. The number of these motifs recorded in 3 min was significantly higher than shuffled spike activity and not seen above chance in control networks in which CA3 was apposed to CA3 or DG to DG. Together, these results demonstrate spontaneous input-dependent repeatable coding of distributed activity in CA3 networks driven by engineered inputs from DG networks. These functional configurations at measured times of activation (motifs) emerge from anatomically accurate feed-forward connections from DG through tunnels to CA3

Study of Dissipative Collisions of 20^{20}Ne (∼\sim7-11 MeV/nucleon) + 27^{27}Al

The inclusive energy distributions of complex fragments (3 $\leq$Z $\leq$ 9) emitted in the reactions $^{20}$Ne (145, 158, 200, 218 MeV) + $^{27}$Al have been measured in the angular range 10$^{o}$ - 50$^{o}$. The fusion-fission and the deep-inelastic components of the fragment yield have been extracted using multiple Gaussian functions from the experimental fragment energy spectra. The elemental yields of the fusion-fission component have been found to be fairly well exlained in the framework of standard statistical model. It is found that there is strong competition between the fusion-fission and the deep-inelastic processes at these energies. The time scale of the deep-inelastic process was estimated to be typically in the range of $\sim$ 10$^{-21}$ - 10$^{-22}$ sec., and it was found to decrease with increasing fragment mass. The angular momentum dissipations in fully energy damped deep-inelastic process have been estimated from the average energies of the deep-inelastic components of the fragment energy spectra. It has been found that, the estimated angular momentum dissipations, for lighter fragments in particular, are more than those predicted by the empirical sticking limit.Comment: 16 pages, 9 figure

Companding to improve cochlearimplant speech recognition in speech-shaped noise,”

Nonlinear sensory and neural processing mechanisms have been exploited to enhance spectral contrast for improvement of speech understanding in noise. The "companding" algorithm employs both two-tone suppression and adaptive gain mechanisms to achieve spectral enhancement. This study implemented a 50-channel companding strategy and evaluated its efficiency as a front-end noise suppression technique in cochlear implants. The key parameters were identified and evaluated to optimize the companding performance. Both normal-hearing ͑NH͒ listeners and cochlear-implant ͑CI͒ users performed phoneme and sentence recognition tests in quiet and in steady-state speech-shaped noise. Data from the NH listeners showed that for noise conditions, the implemented strategy improved vowel perception but not consonant and sentence perception. However, the CI users showed significant improvements in both phoneme and sentence perception in noise. Maximum average improvement for vowel recognition was 21.3 percentage points ͑p Ͻ 0.05͒ at 0 dB signal-to-noise ratio ͑SNR͒, followed by 17.7 percentage points ͑p Ͻ 0.05͒ at 5 dB SNR for sentence recognition and 12.1 percentage points ͑p Ͻ 0.05͒ at 5 dB SNR for consonant recognition. While the observed results could be attributed to the enhanced spectral contrast, it is likely that the corresponding temporal changes caused by companding also played a significant role and should be addressed by future studies

Evidence of large nuclear deformation of 32^{32}S∗^{*} formed in 20^{20}Ne + 12^{12}C reaction

Deformations of hot composite $^{32}$S$^{*}$ formed in the reaction $^{20}$Ne ($\sim$ 7 -- 10 MeV/nucleon) + $^{12}$C have been estimated from the respective inclusive $\alpha$-particle evaporation spectra. The estimated deformations for $^{32}$S$^{*}$ have been found to be much larger than the `normal' deformations of hot, rotating composites at similar excitations. This further confirms the formation of highly deformed long-lived configuration of $^{20}$Ne + $^{12}$C at high excitations ($\sim$ 70 -- 100 MeV) -- which was recently indicated from the analysis of the complex fragment emission data for the same system. Exclusive $\alpha$-particle evaporation spectra from the decay of hot composite $^{32}$S$^{*}$ also show similar behaviour.Comment: 9 pages, 6 figure

Analiza strukturne funkcije nukleona

The square modulus of the wave function of the proton has been derived in the framework of the statistical model. The presence of antiquarks in the sea, which simulates the screening effect, has been explicitly taken into account. The resulting momentum space wavefunction has also been used to estimate the structure function for the free proton as well as the difference in structure function for the proton and neutron. The results obtained are in agreement with the corresponding experimental data and other theoretical estimates. The colour transparency effect has also been studied with interesting consequences.U okviru statističkog modela izveden je izraz za kvadrat modula valne funkcije. Eksplicitno je uzeta u obzir prisutnost antikvarkova iz pozadine koja simulira efekt zasjenjenja. Pomoću Fourierovog transformata valne funkcije određena je strukturna funkcija slobodnog protona i razlika strukturnih funkcija protona i neutrona. Dobiveni rezultati slažu se s odgovarajućim eksperimentalnim vrijednostima i rezultatima drugih teorijskih ocjena. Proučava se, takoder, efekt transparencije boje i izvedene su neke zanimljive posljedice

Analiza strukturne funkcije nukleona

The square modulus of the wave function of the proton has been derived in the framework of the statistical model. The presence of antiquarks in the sea, which simulates the screening effect, has been explicitly taken into account. The resulting momentum space wavefunction has also been used to estimate the structure function for the free proton as well as the difference in structure function for the proton and neutron. The results obtained are in agreement with the corresponding experimental data and other theoretical estimates. The colour transparency effect has also been studied with interesting consequences.U okviru statističkog modela izveden je izraz za kvadrat modula valne funkcije. Eksplicitno je uzeta u obzir prisutnost antikvarkova iz pozadine koja simulira efekt zasjenjenja. Pomoću Fourierovog transformata valne funkcije određena je strukturna funkcija slobodnog protona i razlika strukturnih funkcija protona i neutrona. Dobiveni rezultati slažu se s odgovarajućim eksperimentalnim vrijednostima i rezultatima drugih teorijskih ocjena. Proučava se, takoder, efekt transparencije boje i izvedene su neke zanimljive posljedice

Floral biology and phenological studies of Datura metel L. in Tripura, Northeast India, with special reference to floral morphotypes

Datura metel L. is an important medicinal plants of Tripura. There are four floral morpho-types found throughout India. The floral biology of four morpho-types of D. metel L. collected from different places of Tripura state have been investigated based on their morphological and palynological study. Initiation of the floral bud, anthesis, pollen viability, pollen germination, and pollen production are the topics covered in the present study. The present study includes photographic representations and UPGMA dendrogram for quick identification, as well as a detailed explanation of four morpho-types of the species.