A novel time and wavelength interleaved optical pulsed signal for a high resolution photonic analogue to digital converter

This paper presents a parallel architecture for a photonic Analog to Digital Converter (ADC) in a direct conversion receiver. A novel technique for the generation of time and wavelength interleaved laser source having a broad spectrum and a repetition rate of 8 GHz is proposed for the sampling of the photonic ADC. The quantization is realized in electrical domain by employing four state of the art ADCs , each having a sampling rate of 2 GHz and a resolution of 10 bit. We investigate the performance of our novel architecture by computing the Signal to Noise Ratio and comparing it with the conventional electronic ADC. Additionally we have also observed the effect of laser jitter on the sensitivity of a direct conversion receiver.     

Ring test for ferrous ions

Summary When ethyl alcohol is added to an aqueous solution containing small amount of pantothenic acid, ascorbic acid and Fe(II), beautiful blue ring is formed at the junction of ethyl alcohol-water which is characteristic of ferrous ions. The visual limit of identification is 25 per ml of Fe(II). The maximum tolerable limit of various metal ions which do not interfere with the formation of blue ring is reported.

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Zusammenfassung Überschichtet man eine wäßrige Lösung von Pantothensäure, Ascorbinsäure und Eisen(II) mit Äthylalkohol, so entsteht an der Berührungsstelle der beiden flüssigen Phasen ein blauer Ring, der für Eisen (II) charakteristisch ist. Die Nachweisgrenze beträgt 25 Fe(II)/ml. Für verschiedene störende Metallionen wird die maximal tolerierbare Menge angegeben.

     

A new group of isoquinoline alkaloids : The secoberbines

The new isoquinoline alkaloid (?)-peshawarine (1) has been isolated from Hypecoum parviflorum Kar. & Kir. (Papaveraceae). Its synthesis in the racemic form from coptisine (6b) involves a novel approach to cyclic hemiacetals in which the key step is the transformation of the aldehyde (±)-aobamine (10b) into the hemiacetal 12b using ethyl chloroformate. (±)-Corydalisol (11b) and (±)-canadaline (10a) have also been synthesized for the first time. The absolute configuration of (?)-1 was determined by chemical correlation with (+)-rhoeagenine methiodide (20). The chirality of the alkaloid (+)-canadaline (10a) has also been established by analogy to (+)-corydalisol (11b). (?)-Peshawarine (1), (+)-canadaline (10a), (+)-corydalisol (11b), and aobamine (10b), as well as hypecorine (22) and hypecorinine (23), are members of a new group of isoquinoline alkaloids, the secoberbines.     

Kalashine,a novel type aporphine-benzylisoquinoline alkaloid

$\text{Berberis orthobotrys}$ produces the new dimer kalashine ($\text{1}$), together with the previously reported pakistanamine ($\text{2}$) and pakistanine ($\text{3}$). Kalashine is the first aporphine-benzylisoquinoline known to be substituted at C-11. Acid catalyzed rearrangement of pakistanamine ($\text{2}$) in 3N HCl leads to 1-0-methylpakistanine ($\text{6}$) together with small amounts of 1-0-methylkalashine ($\text{7}$) and (+)-armepavine ($\text{8}$). Rearrangement of $\text{2}$ using methanol containing a little 3N HCl gives about equal amounts of $\text{6}$ and 1,10-di-O-methylpakistanine ($\text{9}$).     

Diastereoselective metal-catalyzed [4 + 2 + 2] carbocyclization reactions utilizing a rhodium N-heterocyclic carbene (NHC) complex: the first example of a rhodium NHC-catalyzed [m + n + o] carbocyclization

The air and moisture stable rhodium N-heterocyclic carbene (NHC) complex, RhCl(IMes)(COD)(IMes =N,N[prime or minute]-bis(2,4,6-trimethylphenyl)imidazole-2-ylidine; COD = 1,5-cyclooctadiene), facilitates a diastereoselective metal-catalyzed [4 + 2 + 2] carbocyclization of 1,6-enynes in the presence of silver triflate and 1,3-butadiene.     

Spectrophotometric determination of uranium with arsenazo-III in the presence of N-cetyl-N,N,N-tri-methylammonium bromide as surfactant

A simple, sensitive and efficient spectrophotometric method is proposed for rapid determination of uranium using arsenazo-III in perchloric acid. The reaction between arsenazo-III and U(VI) was instantaneous in 3 mol L⁻¹ HClO_4. N-cetyl-N,N,N-trimethylammonium bromide was used for increasing the sensitivity and selectivity of the complex. The absorbance remains stable for over 48 h in the presence of surfactant. The method allows the determination of uranium in the range of 1–20 μg g⁻¹ with a molar absorptivity of 3.9 × 10⁵ dm³ mol⁻¹ cm⁻¹ at 681 nm. Sandell’s sensitivity of the complex was calculated to be 6.4 ng cm⁻² at λ_max 681 nm. A significant enhancement was achieved in the sensitivity of the proposed method whereas, Relative Standard Deviation was reduced from 4.5 to 1.7% in the presence of surfactant. Among various diverse ions studied, fluoride, cyanide, citrate, sulfate and phosphate interfere beyond the tolerance limit. Among cations only Cr³⁺ and Co²⁺ decreased the normal absorbance. The validity of the reported method was tested by determining uranium in the environmental water samples and Standard Reference Material. The results agreed closely with the reported values. The proposed method is new, easy in operation and better in sensitivity than many of the existing methods.     

Seimatoric acid and colletonoic acid:Two new compounds from the endophytic fungi,Seimatosporium sp.and Colletotrichum sp.

A new metabolite,named seimatoric acid(1),representing a new oxobutanoic acid derivative has been isolated from Seimatosporium sp., in addition to four known compounds viz.,2-hydroxymethyl-4β,5α,6β-trihydroxycyclohex-2-enone(2),(-)-phyllostine(3),(+)-epiepoxydon(4) and(+)-epoxydon monoacetate(5).Similarly one new benzoic acid derivative,named colletonoic acid(6) was isolated from the ethyl acetate fraction of Colletotrichum sp.The structures of the new compounds were elucidated by detailed ~1 H NMR,~(13)C NMR,COSY,HMQC.HMBC spectroscopic analysis,and HR-E1-MS.Seimatoric acid(1)was also isolated from another taxonomical unidentified fungal strain 4295 in ourgroup.The structures of the known compounds were elucidated by their spectral data comparison to literature data.Preliminary studies showed that colletonoic acid(6) showed good antibacterial,antifungal,and antialgal activities.     

Chemical Enhancement and Quenching in Single-Molecule Tip-Enhanced Raman Spectroscopy

Despite intensive research in surface enhanced Raman spectroscopy (SERS), the influence mechanism of chemical effects on Raman signals remains elusive. Here, we investigate such chemical effects through tip-enhanced Raman spectroscopy (TERS) of a single planar ZnPc molecule with varying but controlled contact environments. TERS signals are found dramatically enhanced upon making a tip–molecule point contact. A combined physico-chemical mechanism is proposed to explain such an enhancement via the generation of a ground-state charge-transfer induced vertical Raman polarizability that is further enhanced by the strong vertical plasmonic field in the nanocavity. In contrast, TERS signals from ZnPc chemisorbed flatly on substrates are found strongly quenched, which is rationalized by the Raman polarizability screening effect induced by interfacial dynamic charge transfer. Our results provide deep insights into the understanding of the chemical effects in TERS/SERS enhancement and quenching.