Femtosecond Photoexcited Carrier Dynamics in Reduced Graphene Oxide Suspensions and Films

We report ultrafast response of femtosecond photoexcited carriers in single layer reduced graphene oxide flakes suspended in water as well as few layer thick film deposited on indium tin oxide coated glass plate using pump-probe differential transmission spectroscopy at 790 nm. The carrier relaxation dynamics has three components: ~200 fs, 1 to 2 ps, and ~25 ps, all of them independent of pump fluence. It is seen that the second component (1 to 2 ps) assigned to the lifetime of hot optical phonons is larger for graphene in suspensions whereas other two time constants are the same for both the suspension and the film. The value of third order nonlinear susceptibility estimated from the pump-probe experiments is compared with that obtained from the open aperture Z-scan results for the suspension.Comment: 4 pages, 4 figures, to appear in International Journal of Nanoscience (IJN), 201

Femtosecond carrier dynamics and saturable absorption in graphene suspensions

Nonlinear optical properties and carrier relaxation dynamics in graphene, suspended in three different solvents, are investigated using femtosecond (80 fs pulses) Z-scan and degenerate pumpprobe spectroscopy at 790 nm. The results demonstrate saturable absorption property of graphene with a nonlinear absorption coefficient, $beta$, of ~2 to 9x10^-8 cm/W. Two distinct time scales associated with the relaxation of photoexcited carriers, a fast one in the range of 130-330 fs (related to carrier-carrier scattering) followed by a slower one in 3.5-4.9 ps range (associated with carrier-phonon scattering) are observed.Comment: 3 pages, 2 figures, 2 table

Detection of Sugar-Lectin Interactions by Multivalent Dendritic Sugar Functionalized Single-Walled Carbon Nanotubes

We show that single walled carbon nanotubes (SWNT) decorated with sugar functionalized poly (propyl ether imine) (PETIM) dendrimer is a very sensitive platform to quantitatively detect carbohydrate recognizing proteins, namely, lectins. The changes in electrical conductivity of SWNT in field effect transistor device due to carbohydrate - protein interactions form the basis of present study. The mannose sugar attached PETIM dendrimers undergo charge - transfer interactions with the SWNT. The changes in the conductance of the dendritic sugar functionalized SWNT after addition of lectins in varying concentrations were found to follow the Langmuir type isotherm, giving the concanavalin A (Con A) - mannose affinity constant to be 8.5 x 106 M-1. The increase in the device conductance observed after adding 10 nM of Con A is same as after adding 20 \muM of a non - specific lectin peanut agglutinin, showing the high specificity of the Con A - mannose interactions. The specificity of sugar-lectin interactions was characterized further by observing significant shifts in Raman modes of the SWNT.Comment: 12 pages, 3 figure

Antimicrobial activity of the fruit extracts of Coccinia indica

The bioactive compounds of fruits of Coccinia indica were investigated for antibacterial activity against some pathogenic bacteria. The aqueous extracts did not show much significant activity, while the organic extracts (petroleum ether and methanol) showed the highest activity against the test bacteria.The activity was more pronounced on gram-positive organisms with Staphylococcus aureus being more susceptible and Salmonella paratyphi A being more resistant. Phytochemical analysis showed that the extracts contain alkaloids, tannins, saponins, flavonoids, glycosides and phenols

Calculation and experimental verification of m drop in tsia electrodes of chlor-alkali cells

A computer program to analyss the current distribution in a chlor-alkali cell using Titanium Substrate Insoluble Anode (TSIA) has baen developed. The program takes into account the polarisation resistance characteristics of anode and camode and the electrolyte resistance, in a d d i i to anode nodal resistance. The results are compared with the experimental data

A Study on “Security of Cyber-Physical Systems in the Cloud”

The existing security models are built with certain assumptions. The solutions like distributed accountability, provable data possession (PDP), Third Party Auditing (TPA) and so on are secure as long as the assumptions hold true. To ensure fool proof security for cloud storage security little research has been made on quantum key cryptography. Since the quantum key distribution is unconditionally secure, we propose a new scheme known as Cloud QKDP (Quantum Key Distribution Protocol for Cloud Computing) which exploits the benefits of quantum mechanisms to secure cloud storage and data dynamics. We consider a case study in which three parties such as cloud server, data owner and trusted client have provably secure communications with our proposed scheme which uses random oracle model. Our empirical study revealed mixture of success and failure rates with private and public clouds respectively

Influence of surgical time on post-surgical visual acuity in patients undergoing small incision cataract surgery: a prospective study

Background: Cataract surgery is one of the commonest surgical procedures in Ophthalmology. This study aimed at evaluating the influence of duration of surgery on post-operative vision in patients who underwent uneventful small incision cataract surgery.Methods: All patients (66.3±8.6 years of age), who underwent small incision cataract surgery after a complete preoperative evaluation. Duration of surgery starting from draping to sub conjunctival injection of amikacin after surgery was noted. The patients were grouped based on surgical time. Best corrected visual acuity was recorded in all patients on post-operative day one and also one month after surgery. The data was subjected to statistical analysis.Results: Ninety one patients were included in this study. More number of patients (47/91) was found in group with 26-35 min surgical time, whereas only 9 patients were found in 46-55 min group. A week correlation was found between surgical timing with PSVA on 1st (r = 0.2034, 95% CI = -0.00772-0.3971, two tailed p = 0.051) or on the 30th day (r= 0.1024; 95% CI = -0.1107-0.3066, two tailed p =0.33). No significant difference was found in the PSVA of 1st day (p=0.699) or 30th day (p=0.150) when compared between the groups. However, the difference was found to be significant between the mean value of POVA between the 1st and 30th day in all groups.Conclusions: Surgical time did not emerge as a significant influence on long term post-operative visual outcome following uncomplicated Small incision cataract surgery.

Cold Atmospheric Pressure Argon Plasma Jet Assisted Degradation of Malachite Green (MG) Aqueous Solution

The oxidative degradation of cold atmospheric pressure plasma assisted degradation of malachite Green (MG) was investigated in this study. Cold atmospheric pressure plasma assisted MG degradation process was carried out as a function various plasma treatment time (05, 10, and 15 mins). The % of degradation and presence carbon content in the plasma treated MG was examined by UV-Visible spectroscopy (UV-Vis) and total organic carbon (TOC) analyzer. Optical emission spectrometer was used to identify formation of various reactive species during in situ plasma treatment. The higher degradation percentage of 90% was obtained after plasma treatment time of 15 min and value of TOC also found to decreased significantly with increasing plasma treatment time.  Toxicity of the plasma-treated MG aqueous solution samples was also examined by Staphylococcus aureus (S.aureus) bacteria