Isolation, identification and culture of the marine rotifer Colurella adriatica Ehrenberg, 1831 (Family: Lepadellidae) from Andaman & Nicobar Islands: A promising live feed for larval rearing of high value shellfishes and finfishes

An extremely small rotifer was isolated from the micro zooplankton samples collected during February, 2014 from Havelock islands of Andaman and Nicobar Islands. The species was identified as Colurella adriatica Ehrenberg, 1831 (Family: Lapadellidae). Its lorica length under culture period ranged from 47.530 to 98.868 μm and width from 34.308 to 56.277 μm. The size of the eggs, neonates and adults are also documented. Comparison of size of C. adriatica with Brachionus plicatilis (L type) and B. rotundiformis (S and SS type) revealed that C. adriatica is smaller in length and width than the SS-type rotifer which is currently used as a first feed in marine tropical fish larval rearing. However, the larvae of many marine food fishes including groupers and high value marine ornamental fishes are unable to consume the SS-type rotifers as a first feed due to their extremely small mouth gape. The culture of C. adriatica was carried out using Nannochloropsis oculata Diet-I), N. oculata and yeast (0.01g/litre) (Diet-II), Yeast (0.01g/litre) alone (Diet-III). Average population density of C. adriatica with these diets reached a maximum of 1000 nos. of individuals /ml on 10th day of culture on feeding with Diet-I; 950 nos. /ml on 14th day (Diet-II) and 650 nos. /ml on 15th day of culture (Diet-III). Diet I &II and Diet II &III did not show any significant difference (P>0.05) whereas, Diet I and III showed significant difference (P<0.01). Preliminary studies of C. adriatica as a feed to the larvae of Stenopus hispidus, Lysmata amboinensis and Pomacentrus caeruleus showed better survival than larvae fed with B. routundiformis during first phase of larval rearing

Johnson-Kendall-Roberts theory applied to living cells

Johnson-Kendall-Roberts (JKR) theory is an accurate model for strong adhesion energies of soft slightly deformable material. Little is known about the validity of this theory on complex systems such as living cells. We have addressed this problem using a depletion controlled cell adhesion and measured the force necessary to separate the cells with a micropipette technique. We show that the cytoskeleton can provide the cells with a 3D structure that is sufficiently elastic and has a sufficiently low deformability for JKR theory to be valid. When the cytoskeleton is disrupted, JKR theory is no longer applicable

Injection locking of a terahertz quantum cascade laser to a telecommunications wavelength frequency comb

High resolution spectroscopy can not only identify atoms and molecules, but can also provide detailed information on their chemical and physical environment, and relative motion. In the terahertz frequency region of the electromagnetic spectrum, where many molecules have fundamental vibrational modes, there is a lack of powerful sources with narrow linewidths that can be used for absorption measurements or as local oscillators in heterodyne detectors. The most promising solid-state source is the THz frequency quantum cascade laser (QCL), however, the linewidth of this compact semiconductor laser is typically too broad for many applications and its frequency is not directly referenced to primary frequency standards. In this work we injection lock a QCL operating at 2 THz to a compact fibre-based telecommunications wavelength frequency comb, where the comb line spacing is referenced to a microwave frequency reference. This results in the QCL frequency locking to an integer harmonic of the microwave reference, and the QCL linewidth reducing to the multiplied linewidth of the microwave reference, < 100 Hz. Furthermore, we perform phase-resolved detection of the locked QCL and measure the phase noise of the locked system to be –75 dBc/Hz at 10 kHz offset from 2 THz carrier

Pump-probe measurements of gain in a terahertz quantum cascade laser

The gain recovery time of a bound-to-continuum terahertz frequency quantum cascade laser, operating at 1.98 THz, has been measured using broadband terahertz-pump-terahertz-probe spectroscopy. The recovery time is found to reduce as a function of current density, reaching a value of 18 ps as the laser is brought close to threshold. We attribute this reduction to improved coupling efficiency between the injector state and the upper lasing level as the active region aligns

Crystal structure of isobutyl 4-(2-chloro-phenyl)-5-cyano-6-{(E)-[(dimethylamino)-methylidene]amino}-2-methyl-4H-pyran-3-carboxylate

The authors thank Dr Babu Varghese, Senior Scientific Officer SAIF, IIT Madras, India, for carrying out the data collection.Peer reviewedPublisher PD

Investigation of time-resolved gain dynamics in an injection seeded terahertz quantum cascade laser

The evolution of the gain of terahertz quantum cascade laser during injection seeding is probed as a function of time. Oscillations of the gain are commensurate with the variations of the field envelope

Terahertz emission mechanism and laser excitation position dependence of nano-grating electrode photomixers

The emission mechanism of continuous wave (CW) terahertz (THz) photomixers that make use of nanostructured gratings (NSGs) is studied. Two different photomixer designs, based on a single-sided NSG and a double-sided NSG, embedded in the same antenna design and fabricated on an Fe doped InGaAsP substrate, are characterized with ∼1550 nm excitation. They are shown to exhibit similar performance in terms of spectral bandwidth and emitted power. The emission is mapped in terms of the laser excitation position, from which the emission mechanism is assigned to an enhanced optical electric field at the tips of the NSGs

Selection of longitudinal modes in a terahertz quantum cascade laser via narrow-band injection seeding

A terahertz quantum cascade laser is injection seeded with narrow-band seed pulses generated from a periodically poled lithium niobate crystal. The spectral emission of the quantum cascade laser is controlled by the seed spectra