Photonic-electronic integrated circuit-based coherent LiDAR engine

Chip-scale integration is a key enabler for the deployment of photonic technologies. Coherent laser ranging or FMCW LiDAR, a perception technology that benefits from instantaneous velocity and distance detection, eye-safe operation, long-range, and immunity to interference. However, wafer-scale integration of these systems has been challenged by stringent requirements on laser coherence, frequency agility, and the necessity for optical amplifiers. Here, we demonstrate a photonic-electronic LiDAR source composed of a micro-electronic-based high-voltage arbitrary waveform generator, a hybrid photonic circuit-based tunable Vernier laser with piezoelectric actuators, and an erbium-doped waveguide amplifier. Importantly, all systems are realized in a wafer-scale manufacturing-compatible process comprising III-V semiconductors, silicon nitride photonic integrated circuits, and 130-nm SiGe bipolar complementary metal-oxide-semiconductor (CMOS) technology. We conducted ranging experiments at a 10-meter distance with a precision level of 10 cm and a 50 kHz acquisition rate. The laser source is turnkey and linearization-free, and it can be seamlessly integrated with existing focal plane and optical phased array LiDAR approaches.

Self-aligned single-electrode actuation of tangential and wineglass modes using PMN-PT

Considering the evolution of rotation sensing and timing applications realized in micro-electro-mechanical systems (MEMS), flexural mode resonant shapes are outperformed by bulk acoustic wave (BAW) counterparts by achieving higher frequencies with both electrostatic and piezoelectric transduction. Within the 1-30 MHz range, which hosts BAW gyroscopes and timing references, piezoelectric and electrostatic MEMS have similar transduction efficiency. Although, when designed intelligently, electrostatic transduction allows self-alignment between electrodes and the resonator for various BAW modes, misalignment is inevitable regarding piezoelectric transduction of BAW modes that require electrode patterning. In this paper transverse piezoelectric actuation of [011] oriented single crystal lead magnesium niobate-lead titanate (PMN-PT) thin film disks are shown to excite the tangential mode and family of elliptical compound resonant modes, utilizing a self-aligned and unpatterned electrode that spans the entire disk surface. The resonant mode coupling is achieved by employing a unique property of [011] PMN-PT, where the in-plane piezoelectric coefficients have opposite signs. Fabricating 1-port disk transducers, RF reflection measurements are performed that demonstrate the compound mode family shapes in the 1-30 MHz range. Independent verification of mode transduction is achieved using in-plane displacement measurements with Polytec's laser Doppler vibrometer (LDV). While the tangential mode achieves a 40^o/s dithering rate at 335 kHz resonant frequency, the n = 2 wine-glass mode achieves 11.46 nm tip displacement at 8.42 MHz resonant frequency on a radius of 60 μm disk resonator in air. A single electrode resonator that can excite both tangential and wine-glass modes with such metrics lays the foundation for a BAW MEMS gyroscope with a built-in primary calibration stage.

Nuclear spin polarization and control in hexagonal boron nitride

Electron spins in van der Waals materials are playing a crucial role in recent advances in condensed-matter physics and spintronics. However, nuclear spins in van der Waals materials remain an unexplored quantum resource. Here we report optical polarization and coherent control of nuclear spins in a van der Waals material at room temperature. We use negatively charged boron vacancy ([Formula: see text]) spin defects in hexagonal boron nitride to polarize nearby nitrogen nuclear spins. We observe the Rabi frequency of nuclear spins at the excited-state level anti-crossing of [Formula: see text] defects to be 350 times larger than that of an isolated nucleus, and demonstrate fast coherent control of nuclear spins. Further, we detect strong electron-mediated nuclear-nuclear spin coupling that is five orders of magnitude larger than the direct nuclear-spin dipolar coupling, enabling multi-qubit operations. Our work opens new avenues for the manipulation of nuclear spins in van der Waals materials for quantum information science and technology.

Optically induced static magnetic field in the ensemble of nitrogen-vacancy centers in diamond

Generation of a local magnetic field at the nanoscale is desirable for many applications such as spin-qubit-based quantum memories. However, this is a challenge due to the slow decay of static magnetic fields. Here, we demonstrate a photonic spin density (PSD)-induced effective static magnetic field for an ensemble of nitrogen-vacancy (NV) centers in bulk diamond. This locally induced magnetic field is a result of coherent interaction between the optical excitation and the NV centers. We demonstrate an optically induced spin rotation on the Bloch sphere exceeding 10 degrees which has potential applications in all-optical coherent control of spin qubits.

Low-noise frequency-agile photonic integrated lasers for coherent ranging

Frequency modulated continuous wave laser ranging (FMCW LiDAR) enables distance mapping with simultaneous position and velocity information, is immune to stray light, can achieve long range, operate in the eye-safe region of 1550 nm and achieve high sensitivity. Despite its advantages, it is compounded by the simultaneous requirement of both narrow linewidth low noise lasers that can be precisely chirped. While integrated silicon-based lasers, compatible with wafer scale manufacturing in large volumes at low cost, have experienced major advances and are now employed on a commercial scale in data centers, and impressive progress has led to integrated lasers with (ultra) narrow sub-100 Hz-level intrinsic linewidth based on optical feedback from photonic circuits, these lasers presently lack fast nonthermal tuning, i.e. frequency agility as required for coherent ranging. Here, we demonstrate a hybrid photonic integrated laser that exhibits very narrow intrinsic linewidth of 25 Hz while offering linear, hysteresis-free, and mode-hop-free-tuning beyond 1 GHz with up to megahertz actuation bandwidth constituting 1.6 × 10¹⁵ Hz/s tuning speed. Our approach uses foundry-based technologies - ultralow-loss (1 dB/m) Si₃N₄ photonic microresonators, combined with aluminium nitride (AlN) or lead zirconium titanate (PZT) microelectromechanical systems (MEMS) based stress-optic actuation. Electrically driven low-phase-noise lasing is attained by self-injection locking of an Indium Phosphide (InP) laser chip and only limited by fundamental thermo-refractive noise at mid-range offsets. By utilizing difference-drive and apodization of the photonic chip to suppress mechanical vibrations of the chip, a flat actuation response up to 10 MHz is achieved. We leverage this capability to demonstrate a compact coherent LiDAR engine that can generate up to 800 kHz FMCW triangular optical chirp signals, requiring neither any active linearization nor predistortion compensation, and perform a 10 m optical ranging experiment, with a resolution of 12.5 cm. Our results constitute a photonic integrated laser system for scenarios where high compactness, fast frequency actuation, and high spectral purity are required.

Stable and tunable integrated lasers are fundamental building blocks for applications from spectroscopy to imaging and communication. Here the authors present a narrow linewidth hybrid photonic integrated laser with low frequency noise and fast linear wavelength tuning. They then provide an efficient FMCW LIDAR demonstration.

High-Contrast Plasmonic-Enhanced Shallow Spin Defects in Hexagonal Boron Nitride for Quantum Sensing

The recently discovered spin defects in hexagonal boron nitride (hBN), a layered van der Waals material, have great potential in quantum sensing. However, the photoluminescence and the contrast of the optically detected magnetic resonance (ODMR) of hBN spin defects are relatively low so far, which limits their sensitivity. Here we report a record-high ODMR contrast of 46% at room temperature and simultaneous enhancement of the photoluminescence of hBN spin defects by up to 17-fold by the surface plasmon of a gold film microwave waveguide. Our results are obtained with shallow boron vacancy spin defects in hBN nanosheets created by low-energy He⁺ ion implantation and a gold film microwave waveguide fabricated by photolithography. We also explore the effects of microwave and laser powers on the ODMR and improve the sensitivity of hBN spin defects for magnetic field detection. Our results support the promising potential of hBN spin defects for nanoscale quantum sensing.

Engineering new limits to magnetostriction through metastability in iron-gallium alloys

Magnetostrictive materials transduce magnetic and mechanical energies and when combined with piezoelectric elements, evoke magnetoelectric transduction for high-sensitivity magnetic field sensors and energy-efficient beyond-CMOS technologies. The dearth of ductile, rare-earth-free materials with high magnetostrictive coefficients motivates the discovery of superior materials. Fe_1-xGa_x alloys are amongst the highest performing rare-earth-free magnetostrictive materials; however, magnetostriction becomes sharply suppressed beyond x = 19% due to the formation of a parasitic ordered intermetallic phase. Here, we harness epitaxy to extend the stability of the BCC Fe_1-xGa_x alloy to gallium compositions as high as x = 30% and in so doing dramatically boost the magnetostriction by as much as 10x relative to the bulk and 2x larger than canonical rare-earth based magnetostrictors. A Fe_1-xGa_x - [Pb(Mg_1/3Nb_2/3)O₃]_0.7-[PbTiO₃]_0.3 (PMN-PT) composite magnetoelectric shows robust 90° electrical switching of magnetic anisotropy and a converse magnetoelectric coefficient of 2.0 × 10^-5 s m^-1. When optimally scaled, this high coefficient implies stable switching at ~80 aJ per bit.

Octave-Tunable Magnetostatic Wave YIG Resonators on a Chip

We have designed, fabricated, and characterized magnetostatic wave (MSW) resonators on a chip. The resonators are fabricated by patterning single-crystal yttrium iron garnet (YIG) film on a gadolinium gallium garnet (GGG) substrate and excited by loop-inductor transducers. We achieved this technology breakthrough by developing a YIG film etching process and fabricating thick aluminum coplanar waveguide (CPW) inductor loop around each resonator to individually address and excite MSWs. At 4.77 GHz, the 0.68-mm² resonator achieves a quality factor ( with a bias field of 987 Oe. We also demonstrate YIG resonator tuning by more than one octave from 3.63 to 7.63 GHz by applying an in-plane external magnetic field. The measured quality factor of the resonator is consistently over 3000 above 4 GHz. The micromachining technology enables the fabrication of multiple single- and two-port YIG resonators on the same chip with all resonators demonstrating octave tunability and high Q .

Hybrid integrated photonics using bulk acoustic resonators

Integrated photonic devices based on Si3N4 waveguides allow for the exploitation of nonlinear frequency conversion, exhibit low propagation loss, and have led to advances in compact atomic clocks, ultrafast ranging, and spectroscopy. Yet, the lack of Pockels effect presents a major challenge to achieve high-speed modulation of Si3N4. Here, microwave-frequency acousto-optic modulation is realized by exciting high-overtone bulk acoustic wave resonances (HBAR) in the photonic stack. Although HBAR is ubiquitously used in modern communication and superconducting circuits, this is the first time it has been incorporated on a photonic integrated chip. The tight vertical acoustic confinement releases the lateral design of freedom, and enables negligible cross-talk and preserving low optical loss. This hybrid HBAR nanophotonic platform can find immediate applications in topological photonics with synthetic dimensions, compact opto-electronic oscillators, and microwave-to-optical converters. As an application, a Si3N4-based optical isolator is demonstrated by spatiotemporal modulation, with over 17 dB isolation achieved.

Observation of Stimulated Brillouin Scattering in Silicon Nitride Integrated Waveguides

Silicon nitride (Si_{3}N_{4}) has emerged as a promising material for integrated nonlinear photonics and has been used for broadband soliton microcombs and low-pulse-energy supercontinuum generation. Therefore, understanding all nonlinear optical properties of Si_{3}N_{4} is important. So far, only stimulated Brillouin scattering (SBS) has not yet been reported. Here we observe, for the first time, backward SBS in fully cladded Si_{3}N_{4} waveguides. The Brillouin gain spectrum exhibits an unusual multipeak structure resulting from hybridization with high-overtone bulk acoustic resonances of the silica cladding. The reported intrinsic Si_{3}N_{4} Brillouin gain at 25 GHz is estimated as 4×10^{-13}  m/W. Moreover, the magnitude of the Si_{3}N_{4} photoelastic constant is estimated as |p_{12}|=0.047±0.004, which is nearly 6 times smaller than for silica. Since SBS imposes an optical power limitation for waveguides, our results explain the capability of Si_{3}N_{4} to handle high optical power, central for integrated nonlinear photonics.

Engineering Electron-Phonon Coupling of Quantum Defects to a Semiconfocal Acoustic Resonator

Diamond-based microelectromechanical systems (MEMS) enable direct coupling between the quantum states of nitrogen-vacancy (NV) centers and the phonon modes of a mechanical resonator. One example, a diamond high-overtone bulk acoustic resonator (HBAR), features an integrated piezoelectric transducer and supports high-quality factor resonance modes into the gigahertz frequency range. The acoustic modes allow mechanical manipulation of deeply embedded NV centers with long spin and orbital coherence times. Unfortunately, the spin-phonon coupling rate is limited by the large resonator size, >100 μm, and thus strongly coupled NV electron-phonon interactions remain out of reach in current diamond BAR devices. Here, we report the design and fabrication of a semiconfocal HBAR (SCHBAR) device on diamond (silicon carbide) with f × Q > 10¹² (>10¹³). The semiconfocal geometry confines the phonon mode laterally below 10 μm. This drastic reduction in modal volume enhances defect center coupling to a mechanical mode by 1000 times compared to prior HBAR devices. For the native NV centers inside the diamond device, we demonstrate mechanically driven spin transitions and show a high strain-driving efficiency with a Rabi frequency of (2π)2.19(14) MHz/V_p, which is comparable to a typical microwave antenna at the same microwave power, making SCHBAR a power-efficient device useful for fast spin control, dressed state coherence protection, and quantum circuit integration.

Rapid Harmonic Analysis of Piezoelectric MEMS Resonators

This paper reports on a novel simulation method combining the speed of analytical evaluation with the accuracy of finite-element analysis (FEA). This method is known as the rapid analytical-FEA technique (RAFT). The ability of the RAFT to accurately predict frequency response orders of magnitude faster than conventional simulation methods while providing deeper insights into device design not possible with other types of analysis is detailed. Simulation results from the RAFT across wide bandwidths are compared to measured results of resonators fabricated with various materials, frequencies, and topologies with good agreement. These include resonators targeting beam extension, disk flexure, and Lamé beam modes. An example scaling analysis is presented and other applications enabled are discussed as well. The supplemental material includes example code for implementation in ANSYS, although any commonly employed FEA package may be used.

A General Analytical Formulation for the Motional Parameters of Piezoelectric MEMS Resonators

This paper reports on a general analytical expression for the motional resistance ( ) of an arbitrary mode in a piezoelectric microelectromechanical system resonator with parallel plate electrode geometry. After applying simplifying assumptions and using analytical modes shapes, expressions for the of modes with out-of-plane flexure as the primary displacement are presented. These modes include free-free transverse beam flexure (TBF), unclamped disk flexure resonators (DFRs), and antisymmetric Lamb modes. For verification, is extracted from resonators fabricated in a lead zirconate titanate on silicon process. Predicted of TBF and DFR modes is validated using on-wafer extracted constants, analytical modal properties, and independently measured material properties.

Mechanical spin control of nitrogen-vacancy centers in diamond

We demonstrate direct coupling between phonons and diamond nitrogen-vacancy (NV) center spins by driving spin transitions with mechanically generated harmonic strain at room temperature. The amplitude of the mechanically driven spin signal varies with the spatial periodicity of the stress standing wave within the diamond substrate, verifying that we drive NV center spins mechanically. These spin-phonon interactions could offer a route to quantum spin control of magnetically forbidden transitions, which would enhance NV-based quantum metrology, grant access to direct transitions between all of the spin-1 quantum states of the NV center, and provide a platform to study spin-phonon interactions at the level of a few interacting spins.

Rayleigh scattering boosted multi-GHz displacement sensitivity in whispering gallery opto-mechanical resonators

Finite photon lifetimes for light fields in an opto-mechanical cavity impose a bandwidth limit on displacement sensing at mechanical resonance frequencies beyond the loaded cavity photon decay rate. Opto-mechanical modulation efficiency can be enhanced via multi-GHz transduction techniques such as piezo-opto-mechanics at the cost of on-chip integration. In this paper, we present a novel high bandwidth displacement sense scheme employing Rayleigh scattering in photonic resonators. Using this technique in conjunction with on-chip electrostatic drive in silicon enables efficient modulation at frequencies up to 9.1GHz. Being independent of the drive mechanism, this scheme could readily be extended to piezo-opto-mechanical and all optical transduced systems.

A silicon electromechanical photodetector

Optomechanical systems have enabled wide-band optical frequency conversion and multichannel all-optical radio frequency amplification. Realization of an on-chip silicon communication platform is limited by photodetectors needed to convert optical information to electrical signals for further signal processing. In this paper we present a coupled silicon microresonator, which converts near-IR optical intensity modulation at 174.2 MHz and 1.198 GHz into motional electrical current. This device emulates a photodetector which detects intensity modulation of continuous wave laser light in the full-width-at-half-maximum bandwidth of the mechanical resonance. The resonant principle of operation eliminates dark current challenges associated with convetional photodetectors. While the results presented here constitute a purely classical demonstration, the device can also potentially be extended to the quantum regime to realize a photon-phonon translator.

Electrode-shaping for the excitation and detection of permitted arbitrary modes in arbitrary geometries in piezoelectric resonators

This paper reports theoretical analysis and experimental results on a numerical electrode shaping design technique that permits the excitation of arbitrary modes in arbitrary geometries for piezoelectric resonators, for those modes permitted to exist by the nonzero piezoelectric coefficients and electrode configuration. The technique directly determines optimal electrode shapes by assessing the local suitability of excitation and detection electrode placement on two-port resonators without the need for iterative numerical techniques. The technique is demonstrated in 61 different electrode designs in lead zirconate titanate (PZT) thin film on silicon RF micro electro-mechanical system (MEMS) plate, beam, ring, and disc resonators for out-of-plane flexural and various contour modes up to 200 MHz. The average squared effective electromechanical coupling factor for the designs was 0.54%, approximately equivalent to the theoretical maximum value of 0.53% for a fully electroded length-extensional mode beam resonator comprised of the same composite. The average improvement in S(21) for the electrode-shaped designs was 14.6 dB with a maximum improvement of 44.3 dB. Through this piezoelectric electrodeshaping technique, 95% of the designs showed a reduction in insertion loss.

A monolithic radiation-pressure driven, low phase noise silicon nitride opto-mechanical oscillator

Cavity opto-mechanics enabled radiation pressure (RP) driven oscillators shown in the past offer an all optical Radio Frequency (RF) source without the need for external electrical feedback. However these oscillators require external tapered fiber or prism coupling and non-standard fabrication processes. In this work, we present a CMOS compatible fabrication process to design high optical quality factor opto-mechanical resonators in silicon nitride. The ring resonators designed in this process demonstrate low phase noise RP driven oscillations. Using integrated grating couplers and waveguide to couple light to the micro-resonator eliminates 1/f(3) and other higher order phase noise slopes at close-to-carrier frequencies present in previous demonstrations. We present an RP driven opto-mechanical oscillator (OMO) operating at 41.97 MHz with a signal power of -11 dBm and phase noise of -85 dBc/Hz at 1 kHz offset with only 1/f(2) noise down to 10 Hz offset from carrier.

Electrostatic actuation of silicon optomechanical resonators

Cavity optomechanical systems offer one of the most sensitive methods for detecting mechanical motion using shifts in the optical resonance frequency of the optomechanical resonator. Presently, these systems are used for measuring mechanical thermal noise displacement or mechanical motion actuated by optical forces. Electrostatic capacitive actuation and detection have been shown previously for silicon micro electro mechanical resonators for application in filters and oscillators. Here, we demonstrate monolithic integration of electrostatic capacitive actuation with optical sensing using silicon optomechanical disk resonators and waveguides. The electrically excited mechanical motion is observed as an optical intensity modulation when the input electrical signal is at a frequency of 235 MHz corresponding to the radial vibrational mode of the silicon microdisk.

PZT transduction of high-overtone contour-mode resonators

This paper presents the Butterworth-van Dyke model and quantitative comparison that explore the design space of lead zirconate titanate-only (PZT) and PZT on 3-, 5-, and 10-μm single-crystal silicon (SCS) high-overtone width-extensional mode (WEM) resonators with identical lateral dimensions for incorporation into radio frequency microelectromechanical systems (RF MEMS) filters and oscillators. A novel fabrication technique was developed to fabricate the resonators with and without a silicon carrier layer using the same mask set on the same wafer. The air-bridge metal routings were implemented to carry electrical signals while avoiding large capacitances from the bond-pads. We theoretically derived and experimentally measured the correlation of motional impedance (RX), quality factor (Q), and resonance frequency (f) with the resonators' silicon layer thickness (tSi) up to frequencies of operation above 1 GHz.

The resonant body transistor

This paper introduces the resonant body transistor (RBT), a silicon-based dielectrically transduced nanoelectromechanical (NEM) resonator embedding a sense transistor directly into the resonator body. Combining the benefits of FET sensing with the frequency scaling capabilities and high quality factors (Q) of internal dielectrically transduced bar resonators, the resonant body transistor achieves >10 GHz frequencies and can be integrated into a standard CMOS process for on-chip clock generation, high-Q microwave circuits, fundamental quantum-state preparation and observation, and high-sensitivity measurements. An 11.7 GHz bulk-mode RBT is demonstrated with a quality factor Q of 1830, marking the highest frequency acoustic resonance measured to date on a silicon wafer.

Nanophotonic devices on thin buried oxide Silicon-On-Insulator substrates

We demonstrate a silicon photonic platform using thin buried oxide silicon-on-insulator (SOI) substrates using localized substrate removal. We show high confinement silicon strip waveguides, micro-ring resonators and nanotapers using this technology. Propagation losses for the waveguides using the cutback method are 3.88 dB/cm for the quasi-TE mode and 5.06 dB/cm for the quasi-TM mode. Ring resonators with a loaded quality factor (Q) of 46,500 for the quasi-TM mode and intrinsic Q of 148,000 for the quasi-TE mode have been obtained. This process will enable the integration of photonic structures with thin buried oxide SOI based electronics.

Internal dielectric transduction: optimal position and frequency scaling

We propose the optimal design for "internal dielectric transduction" of longitudinal bulk mode resonators. This transduction increases in efficiency as the dielectric thickness approaches half the acoustic wavelength. With dielectric films at positions of maximum strain (minimum displacement) in the resonator, 60 GHz resonators are proposed with 50 Omega motional impedance.

Basic fibroblast growth factor inhibits cell proliferation in cultured avian inner ear sensory epithelia

Postembryonic production of inner ear hair cells occurs after insult in nonmammalian vertebrates. Recent studies suggest that the fibroblast family of growth factors may play a role in stimulating cell proliferation in mature inner ear sensory epithelium. Effects of acidic fibroblast growth factor (FGF-1) and basic fibroblast growth factor (FGF-2) were tested on progenitor cell division in cultured auditory and vestibular sensory epithelia taken from posthatch chickens. The effects of heparin, a glycosaminoglycan that often potentiates the effects of the FGFs, were also assessed. Tritiated-thymidine autoradiographic techniques and 5-bromo-2;-deoxyuridine (BrdU) immunocytochemistry were used to identify cells synthesizing DNA. The terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP)-biotin nick-end-label (TUNEL) method was used to identify apoptotic cells. TUNEL and overall counts of sensory epithelial cell density were used to assess possible cytotoxic effects of the growth factors. FGF-2 inhibited DNA synthesis in vestibular and auditory sensory epithelia and was not cytotoxic at the concentrations employed. FGF-1 did not significantly alter sensory epithelial cell proliferation. Heparin by itself inhibited DNA synthesis in the vestibular sensory epithelia and failed to potentiate the effects of FGF-1 or FGF-2. Heparin was not cytotoxic at the concentrations employed. Results presented here suggest that FGF-2 may be involved in inhibiting cell proliferation or stimulating precursor cell differentiation in avian inner ear sensory epithelia.

Fulminant hepatic failure: etiology, viral markers and outcome

OBJECTIVE

To investigate the etiology and outcome of fulminant hepatic failure (FHF) in children.

SETTING

Hospital based descriptive.

METHODS

36 children (22 males and 14 females) presenting with FHF over a period of one year were investigated. The ages ranged from 1.5 to 9 years. FHF was defined as occurrence of encephalopathy within eight weeks of onset of jaundice with no evidence of pre-existing liver disease. Detailed history, clinical examination, routine biochemical parameters and relevant diagnostic tests were carried out. Viral markers studied were anti HAV-IgM, HBsAg, anti HBc-IgM, anti-HCV and anti HEV-IgM.

RESULTS

A viral etiology could be established in 22 children (61.1%). Hepatitis A (n = 12), Hepatitis B (n = 3), Hepatitis A and B (n = 2), and Hepatitis A and E (n = 4). Two children had enteric fever (1 with associated HEV), 2 children had Wilson's disease, 1 child had Indian Childhood Cirrhosis (ICC) and 2 children had drug induced hepatitis. Etiological diagnosis was not possible in 8 children (22%). Fourteen children (39%) died. Poor outcome was associated with spontaneous bleeding, raised prothrombin time, lower transaminases and higher bilirubin on admission.

CONCLUSION

Viral hepatitis is the commonest cause of FHF in children. HAV alone or in combination is responsible for upto 50% of all FHF in children. Chronic liver disease can also present as FHF. Etiological diagnosis is not possible to upto one-fourth of all cases.

Macrophage and microglia-like cells in the avian inner ear

Recent studies suggest that macrophages may influence early stages of the process of hair cell regeneration in lateral line neuromasts; numbers of macrophages were observed to increase prior to increases in hair cell progenitor proliferation, and macrophages have the potential to secrete mitogenic growth factors. We examined whether increases in the number of leukocytes present in the in vivo avian inner ear precede the proliferation of hair cell precursors following aminoglycoside insult. Bromodeoxyuridine (BrdU) immunohistochemistry was used to identify proliferating cells in chicken auditory and vestibular sensory receptor epithelia. LT40, an antibody to the avian homologue of common leukocyte antigen CD45, was used to label leukocytes within the receptor epithelia. Macrophages and, surprisingly, microglia-like cells are present in normal auditory and vestibular sensory epithelia. After hair cell loss caused by treatment with aminoglycosides, numbers of macrophage and microglia-like cells increase in the sensory epithelium. The increase in macrophage and microglia-like cell numbers precedes a significant increase in sensory epithelial cell proliferation. The results suggest that macrophage and microglia-like cells may play a role in releasing early signals for cell cycle progression in damaged inner ear sensory epithelium.

Long term survival in Indian childhood cirrhosis treated with D-penicillamine

Indian childhood cirrhosis (ICC) is an almost uniformly fatal disease whose outcome may be modified with penicillamine if given at a sufficiently early stage. Twenty nine children with ICC seen in Pune, India, in 1980-7, who had survived at least five years from onset of penicillamine treatment, were reviewed aged 6.3 to 13 years. They were assessed clinically, biochemically, histologically, and by duplex Doppler ultrasound examination. None had symptoms suggestive of liver disease. There were no toxic effects of penicillamine other than asymptomatic proteinuria. Hepatosplenomegaly reduced significantly and liver function tests returned to normal in all. In four children, significant hepatosplenomegaly was associated with an abnormal duplex Doppler hepatic vein flow pattern and micronodular cirrhosis on biopsy. Clinical findings, growth and development, and ultrasound examination were normal in the remainder. Review of serial liver biopsy specimens showed a sequence of recovery from ICC through inactive micronodular cirrhosis to virtually normal histological appearances. The four children who still have micronodular cirrhosis beyond four years from onset remain on penicillamine treatment. In the others penicillamine was stopped after 1-7 (mean 3.5) years without relapse, strong evidence that ICC is not due to an inborn error of copper metabolism.

Cell cycle progression in gentamicin-damaged avian cochleas

Hair cells, the sensory receptors of the auditory, vestibular, and lateral-line organs, may be damaged by a number of agents including aminoglycoside antibiotics and severe overstimulation. In the avian cochlea, lost hair cells can be replaced by regeneration. These new hair cells appear to be derived from a support cell precursor which is stimulated to divide by events associated with hair cell loss. Little is known about the timing and sequencing of events leading to new hair cell production. In this study cell cycle-associated events in the avian cochlea were analyzed at early and late time intervals following a single high dose of gentamicin. This single dose protocol has been shown to consistently result in extensive morphological damage and hair cell loss in the proximal region of the cochlea while sparing a morphologically undamaged distal cochlear region. This allowed for the differential analysis of the underlying support cell populations with respect to local hair cell loss. Three cell cycle associated markers were used to evaluate which cells entered and progressed through the cell cycle: statin, a G0 associated nuclear marker; proliferating cell nuclear antigen (PCNA), a G1, S and G2 associated marker; and 5-bromodeoxyuridine (BrdU), an S phase associated marker. Using these markers we found evidence for reversible changes in cell cycle status throughout the cochlea, while progression through S phase and mitosis was restricted to the region of the cochlea which sustained hair cell loss.

Parenteral nutrition (PN) in the management of very low birth weight (VLBW) babies--a randomized controlled trial

Eighty five very low birth weight (VLBW) babies with birthweight less than 1250 g were randomly assigned such that 43 received parenteral nutrition (PN) with amino acid based glucose electrolyte solution (Vamin) and lipid emulsion (Intralipid) in the first 16 days of life. The other 42 (control group) received conventional intravenous dextrose with or without electrolytes plus enteral milk regimen. Baseline clinical parameters and neonatal problems encountered in the two groups were similar. There was no significant difference in the mortality rate in the two groups (48.9% in PN group and 42.9% in control group: X2 = 0.3, p > 0.05). The commonest cause of mortality in both the groups was septicemia (16.3% and 26.1% in PN and control groups, respectively). Local complications, sepsis and fluid electrolyte disturbances were similar in the two groups. Azotemia (25.6%), hyperlipidemia (9.3%), metabolic acidosis (9.3%) and prolonged cholestasis (14%) were commoner in the PN group but were reversible with early recognition. Time taken to regain birthweight was also similar in the two groups (X2 = 14.2 and 15.2 days for PN and control groups, respectively). Thus, PN failed to improve the survival or early weight gain in the routine management of the VLBW babies in our unit.

Reversal of Indian childhood cirrhosis by D-penicillamine therapy

Serial liver biopsy changes have been reviewed in 30 patients with Indian childhood cirrhosis (ICC) who were randomly allocated to receive treatment with penicillamine in a dose of 20 mg/kg/day, 10 of whom also received prednisolone, and five receiving placebo. The latter died within 185 (mean, 149) days of starting treatment. Nine receiving penicillamine died within 540 (mean, 338) days, but the remainder are well 5.1-9.3 years after commencing treatment. Initial biopsies showed severe hepatocellular injury, pericellular fibrosis, inflammatory infiltration, and orcein-staining granules. Second biopsies taken within 6 months of starting penicillamine usually showed persistence of inflammation and an increase in nodularity with thick and thin active septae. Subsequently the appearances were of an inactive micronodular cirrhosis, with reduction in septal inflammatory infiltrate, hepatocellular injury, and intensity of orcein staining. This further improved to a stage of incomplete fibrous septae. The last liver biopsies at 6-60 months (in 21 survivors) showed almost normal histology in four, incomplete fibrous septae in five, and inactive micronodular cirrhosis with thin septae in 12. Mean liver copper concentrations decreased from 1,407 (SEM, 121) micrograms/g at presentation to 925 (183), 317 (100), and 127 (35) at 6, 6-18, and > 18 months after starting treatment. By contrast, a second biopsy taken in the 6 months after diagnosis in placebo-treated children showed persistence of ICC with increase in inflammation, fibrosis, and orcein staining.

Catch up growth and its determinants in low birth weight babies: a study using Z scores

Two hundred and forty seven low birthweight (LBW) survivors of our Neonatal Intensive Care Unit and 164 normal birthweight controls were followed up longitudinally from birth to 4 years and their growth trends (weight, height, head circumference) were expressed as mean Z scores in 500 g birthweight categories. Whereas LBW's demonstrated rapid growth in the first 6 months of life, followed by generally parallel trends with some tendency to rise, controls showed distinct growth faltering especially after one year. Only 30.8% of LBWs (and 49% of controls) were within the designated catch up levels for weight by age 4 years. The corresponding number for catch up of height and head circumference in LBW's was 22.8% and 26.5%, respectively. On multiple regression analysis, the most important determinants of catch up (at 4 years) in LBW's were weight at 1 year (beta = 0.51), height at 1 year (beta = 0.31) and mother's weight (beta = 0.04). Thus, Z scores enabled the demonstration of changing growth trends, simultaneous comparisons with local controls and international standards and comparison within indices. Growth charts incorporating Z score should be made available in a simplified manner for use in the community.

Vegetable oil fortified feeds in the nutrition of very low birthweight babies

Two kinds of oils (i) Polyunsaturated fatty acids (PUFA) rich Safflower oil, and (ii) Medium chain triglyceride (MCT) rich Coconut oil were added to the feeds of 46 very low birthweight (VLBW) babies to see if such a supplementation is capable of enhancing their weight gain. Twenty two well matched babies who received no fortification served as controls. The oil fortification raised the energy density of the feeds from approximately 67 kcal/dl to 79 kcal/dl. Feed volumes were restricted to a maximum of 200 ml/kg/day. The mean weight gain was highest and significantly higher than the controls in the Coconut oil group (19.47 +/- 8.67 g/day or 13.91 g/day). Increase in the triceps skinfold thickness and serum triglycerides were also correspondingly higher in this group. The lead in the weight gain in this group continued in the follow up period (corrected age 3 months). As against this, higher weight gain in Safflower oil group (13.26 +/- 6.58 g/day) as compared to the controls (11.59 +/- 5.33 g/day), failed to reach statistically significant proportions, probably because of increased statistically significant proportions, probably because of increased steatorrhea (stool fat 4+ in 50% of the samples tested). The differences in the two oil groups are presumably because of better absorption of MCT rich coconut oil. However, individual variations in weight gain amongst the babies were wide so that some control babies had higher growth rates than oil fortified ones. The technique of oil fortification is fraught with dangers of intolerance, contamination and aspiration. Long term effects of such supplementation are largely unknown.(ABSTRACT TRUNCATED AT 250 WORDS)

The prevention of Indian childhood cirrhosis

Previous studies have led to the hypothesis that the gross hepatic copper storage characteristic of Indian childhood cirrhosis (ICC) is due to the early introduction of animal milk feeds which have been contaminated with copper from brass household utensils. Amongst the families of 100 cases of ICC, the incidence of ICC in children born after dietary advice had been given (1/86) was significantly lower than in older siblings (12/125). This study attempted to document the incidence of ICC and the usage of brass before and after an intervention programme in Pune District advising against this pattern of infant feeding. The study encountered numerous difficulties in data gathering, but documented a fall in ICC prevalence resulting in its virtual disappearance in Pune District. This contrasted with an unchanged incidence in Chandigarh. Although a fall in brass usage was seen in Pune District, this was actually a spontaneous sociological change rather than a result of health education.

Reduction in parenteral nutrition related complications in the newborn

A comparison of total parenteral nutrition (TPN) related complication in newborns was made between two study periods, namely, 1986 (Study A) and 1989-90 (Study B). A significant reduction was seen in all complications in Study B. Local complications (thrombophlebitis, gangrene, abscess) reduced from 80.0 to 29.4%, septicemia from 52.0 to 11.7% and metabolic complications from a computed mean of 1.6 episode per baby to 0.88 episode per baby. The reduction in these complications has been attributed to the following additional inputs in the recent study (i) Additional staff (research officers, nurses, biochemist); (ii) Better training of resident staff; (iii) Use of a laminar flow system for mixing solutions; (iv) Specially designed locally manufactured intravenous sets and accessories; and (v) Use of well balanced nutrient solutions. Outstanding problems perceived are--high incidence of TPN-related cholestasis (14.7%), azotemia (26.4%), central catheter-related sepsis (75.0%) and the falling, but yet high cost of the technique (Rs. 650 per day).

Trends in perinatal and neonatal mortality and morbidity in India

Although the infant mortality rate (IMR) has reduced by 50% during the past century, it compares poorly with the advanced countries and some developing countries. The observed fall in IMR has been mostly in post-neonatal mortality, with the result that neonatal deaths now account for over 60% of all infant deaths. The overall perinatal mortality rate (PMR) in India is still over 50 per 1000 and has shown virtually no decline during the past decade, However, PMR differs widely in different states, urban/rural areas, different hospitals and so on. PMR is seen to correlate better with social development than economic development of the representative community. The causes of perinatal deaths suggest poor health of mother and poor health facilities and are hence potentially preventable. Various studies have shown that PMR can be significantly reduced within a short span of time. The registration of vital statistics continue to be highly unsatisfactory especially in rural areas.

Copper in urine and hair in Indian childhood cirrhosis

In advanced Indian childhood cirrhosis (ICC) urine copper concentration was higher (range 416-103,448 mg/g creatinine) than in other hepatic diseases (range 67-10,303 mg/g creatinine). In early ICC urine copper concentration was more modestly raised (1188-9470 mg/g creatinine), but rose to high values (2222-42,819 mg/g creatinine) after a single dose of penicillamine 20 mg/kg. A post-penicillamine urinary copper:creatinine ratio greater than 10,000 mg/g supports a diagnosis of ICC. The concentration of copper in the hair, while increased in advanced ICC, is of no diagnostic value in early cases.

Clinical trials of penicillamine in Indian childhood cirrhosis

The outcome in 15 children with advanced Indian childhood cirrhosis (ICC) treated with penicillamine 20 mg/kg/day was not significantly different from that in untreated children. Among children admitted to a further double blind trial who had ICC but who had not yet developed jaundice or ascites 10 treated with penicillamine and 10 treated with penicillamine plus prednisolone had a significantly improved survival. Fourteen of 29 treated cases made a clinical recovery and were alive 489 to 1460 days from the start of treatment. Biopsy specimens in survivors showed a return to normal liver histology in three, residual fibrosis in six, and inactive micronodular cirrhosis in five. Thus penicillamine, while not shown to be beneficial in advanced ICC, lowered mortality from 93% to 52% in preicteric cases of ICC.

Comparison of feeding history of children with Indian childhood cirrhosis and paired controls

One hundred prospectively studied children with Indian childhood cirrhosis (ICC) in Pune District, India, differed from 100 matched controls with respect to feeding history. Animal milk was used in all ICC cases but not in 27 controls. It had been started by 3 months in 63 cases and by 6 months in 82 cases of ICC, as compared with 15 and 25 controls. Twenty-four ICC cases received no breast feeding, and 45 and 60 were breast fed for less than 3 and less than 6 months, respectively; only 10 control children were breast fed for less than 6 months. All ICC children's feeds had been in contact with brass vessels. Copper vessels were used for water carriage with equal frequency in cases and controls. Girls predominated amongst healthy older siblings of cases. Ninety-one healthy siblings of cases had been fed similarly to controls. Three pairs of twins with similar feeding histories died with ICC, whereas two pairs were discordant for feeding and outcome. Hepatic copper loading in ICC is attributable to copper contamination of early animal milk feeds.

Early introduction of copper-contaminated animal milk feeds as a possible cause of Indian childhood cirrhosis

Brass and copper household utensils are a possible source of the gross hepatic copper accumulation characteristic of Indian childhood cirrhosis (ICC). In 107 families with a child with ICC, the use of copper or brass for water storage (97%) and of brass for milk storage (90%) or milk boiling (67%) resembled that of neighbouring village control families. However, the feeding history of 132 children with ICC differed from that of 70 children with other hepatic disorders and 311 children in 2 rural control groups. No child with ICC was exclusively breast-fed whereas 10%, 32%, and 25% of the control children were. Duration of breast-feeding was shorter in children with ICC and animal milk was introduced earlier. 57% were started on animal milk before 3 months of age. The age at introduction of animal milk correlated with the age at presentation with ICC. 66 urban Pune children had a feeding history similar to those with ICC, but in these families brass vessels were not used for milk. Experimentally, milk took up copper from utensils more avidly than water did. The copper concentration in milk samples obtained from ICC households, and those obtained experimentally, would supply a copper intake 6 to 20 times greater than that of the breast-fed infant, and similar to that producing copper toxicosis in the lamb. The hypothesis that early introduction of copper contaminated animal milk is of aetiological importance explains many of the epidemiological features of ICC.

Liver disease in India

One hundred and twenty-five children with chronic liver disease were seen in Pune in 13 months. Fifty-nine of them, aged 8-39 months, had Indian childhood cirrhosis histologically diagnosed. Their characteristics included an insidious onset of symptoms, a geographical clustering of cases in rural areas north-east of Pune, a high rate of parental consanguinity and affected siblings, and a very high hepatic copper concentration (790-6654 micrograms/g dry weight). Only 8 survived for 6 months, adverse prognostic features being jaundice, ascites, enlargement of the gall bladder, and severe anaemia at presentation. Clinical differentiation from other liver disorders in the same age group was clear in advanced cases but unreliable in earlier cases. Four asymptomatic siblings with hepatomegaly had a benign course. The need for non-invasive methods to diagnose early cases in the community is demonstrated. The other major diagnostic categories were: unresolved hepatitis (12); chronic active hepatitis (7); cryptogenic cirrhosis (6); neonatal hepatitis and biliary atresia (8).

Pasteurella multocida meningitis in an infant with recovery

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