Local Transmitter Research Articles

System study on nonlinear suppression of varying-envelope local interference in multimode transceivers

In multimode transceivers, a local transmitter may induce a strong interference in a local receiver, often several orders of magnitude stronger than the desired received signal. To suppress this interference linearly, the receiver would need a very large dynamic range, resulting in excessive power consumption. A potentially much more power-efficient approach involves a memoryless nonlinearity that can strongly suppress the interference when accurately adapted to the envelope of the interference. This approach has so far been limited to constant-envelope interferers owing to the difficulty of extracting accurate interference envelope information from the compound received signal. In this paper, we observe that in multimode transceivers the locally available baseband interference enables accurate adaptation for varying-envelope interferences. The paper performs a system study to explore the resulting performance. Specifically, we show that for varying-envelope interferences, nonlinear distortion products emerge that are negligible for constant-envelope interferences. We analyze these products, identify the conditions for which adequate interference suppression is combined with negligible distortion, and show that these conditions are met in most cases of practical interest. Simulations for a broad set of modulation schemes corroborate this analysis.

안경 렌즈의 국소적 투과율 측정을 위한 방법에 관한 연구

목적: 국소 투과율 현미경을 이용하여 안경렌즈의 투과율 분포를 분석함으로써 렌즈의 광학적 균질성을 연구하고자 한다. 방법: 안경렌즈 표면에 집광된 레이저의 투과율을 광검출기와 락인앰프로 측정하고 그 결과를 분석하였다. 코팅되지 않은 렌즈와 멀티 코팅이 된 렌즈 그리고 누진렌즈가 시료로서 분석되었다. 결과: 누진렌즈와 물리적 자극이 가해진 렌즈의 측정 결과에서 국소 투과율 현미경 분석 결과가 광학 현미경을 통한 측정 결과와 높은 일치도를 보였다. 또한 광학적 결함이 있는 곳에서 투과율의 평균값은 감소하고 표준편차는 증가하였다. 자극이 가해지지 않은 렌즈에서는 반사방지 코팅의 유무가 투과율에 큰 영향을 미치는 것을 국소 투과율 현미경과 일반적 투과율 분석 모두에서 공통적으로 분석되었다. 결론: 시료에 다양한 자극이 가해졌을 때 투과율의 분포에 변화가 생김을 국소 투과율 현미경을 통해 확인하였다. 국소 투과율 현미경을 통한 이러한 분석은 렌즈 혹은 코팅막의 균일도를 평가 혹은 확인할 수 있는 하나의 방법으로 활용될 수 있다. Purpose: We have analyzed the transmittance distribution of the ocular lens using local transmittance microscope to investigate the optical homogeneity of the lens. Methods: The transmittance of the laser which is focused on the surface of the ocular lens was measured by using the photo-detector and lock-in amplifier and analyzed. Multi-coated, uncoated, and progressive lenses were analyzed. Results: In the measurement of the progressive lens and a physical stimulated lens, local transmittance microscopy analysis showed a high degree of match with the measurement results through the optical microscope. In addition, the average value of the transmittance is reduced and the standard deviation was increased in the presence of optical defects. In unstimulated lens, there are a large impact on transmittance whether the anti-reflective coating is presence or absence in both the local transmittance microscopy and general transmittance analysis. Conclusions: The distribution of the transmittance measured by local transmission microscopy were changed when the various stimulus is applied to the lenses. These analyzes by local transmission microscopy can be utilized as a way to evaluate or determine the uniformity of the coating film or lens.

A novel electromagnetic interference resisting local interconnection network transmitter

A novel electromagnetic interference resisting local interconnection network transmitter

Local specific absorption rate (SAR), global SAR, transmitter power, and excitation accuracy trade-offs in low flip-angle parallel transmit pulse design.

We propose a constrained optimization approach for designing parallel transmit (pTx) pulses satisfying all regulatory and hardware limits. We study the trade-offs between excitation accuracy, local and global specific absorption rate (SAR), and maximum and average power for small flip-angle pTx (eight channels) spokes pulses in the torso at 3 T and in the head at 7 T. We compare the trade-offs between the above-mentioned quantities using the L-curve method. We use a primal-dual algorithm and a compressed set of local SAR matrices to design radio-frequency (RF) pulses satisfying all regulatory (including local SAR) and hardware constraints. Local SAR can be substantially reduced (factor of 2 or more) by explicitly constraining it in the pulse design process compared to constraining global SAR or pulse power alone. This often comes at the price of increased pulse power. Simultaneous control of power and SAR is needed for the design of pTx pulses that are safe and can be played on the scanner. Constraining a single quantity can create large increase in the others, which can then rise above safety or hardware limits. Simultaneous constraint of local SAR and power is fast enough to be applicable in a clinical setting.

ANODR-ECC Key Management protocol with TELNET to secure Application and Network layer for Mobile Adhoc Networks

A mobile ad hoc network (MANETs) is a self-organizing network that consists of mobile nodes that are connected through wireless media. A number of unique features, such as lack of infrastructural or central administrative supports, dynamic network topologies, open communication channels, and limited device capabilities and bandwidths, have made secure, reliable and efficient routing operations in MANET a challenging task. The ultimate goal of the security solutions for MANET is to provide security services, such as authentication, confidentiality, integrity, anonymity, and availability to mobile users. To achieve the goals, the security solution need for entire protocol stack. . The proposed protocol ANODRECC with Telnet provide application layer security and it ensures route anonymity and location privacy and is robust against eavesdropping attack.For route anonymity, it prevents strong adversaries from tracing a packet flow back to its source or destination; for location privacy, it ensures that adversaries cannot discover the real identities of local transmitters. The simulation is done using network simulator qualnet 5.0 for different number of mobile nodes. The proposed model has exposed improved results in terms of Average throughput, Average end to end delay, Average packet delivery ratio and Average jitter.

Differential dynamics and activity-dependent regulation of α- and β-neurexins at developing GABAergic synapses

Neurexins (NRXs) and neuroligins are key synaptic adhesion molecules that also recruit synaptic signaling machineries. Neurexins consist of α- and β-isoforms, but how they couple synaptic transmission and adhesion to regulate activity-dependent synapse development remains unclear, in part because of poor understanding of their cell biology and regulation in the relevant neurons. Here, we examined the subaxonal localization, dynamics, and regulation of NRX1α and NRX1β in cortical perisomatic inhibitory synapses. Both isoforms are delivered to presynaptic terminals but show significant and different turnover rate at the membrane. Although NRX1α is highly diffuse along developing axons and filopodia, NRX1β is strictly anchored at terminals through binding to postsynaptic ligands. The turnover rate of NRX1β is attenuated by neural activity and presynaptic GABA(B) receptors. NRXs, thus, are intrinsically dynamic but are stabilized by local transmitter release. Such an activity-adjusted adhesion system seems ideally suited to rapidly explore and validate synaptic partners guided by synaptic transmission.

Intrarenal Purinergic Signaling in the Control of Renal Tubular Transport

Renal tubular epithelial cells receive hormonal input that regulates volume and electrolyte homeostasis. In addition, numerous intrarenal, local signaling agonists have appeared on the stage of renal physiology. One such system is that of intrarenal purinergic signaling. This system involves all the elements necessary for agonist-mediated intercellular communication. ATP is released from epithelial cells, which activates P2 receptors in the apical and basolateral membrane and thereby modulates tubular transport. Termination of the signal is conducted via the breakdown of ATP to adenosine. Recent far-reaching advances indicate that ATP is often used as a local transmitter for classical sensory transduction. This transmission apparently also applies to sensory functions in the kidney. Locally released ATP is involved in sensing of renal tubular flow or in detecting the distal tubular load of NaCl at the macula densa. This review describes the relevant aspects of local, intrarenal purinergic signaling and outlines its integrative concepts.

以较高空间分辨率测量可变形薄膜的透射率

An apparatus for localized transmittance measurements of optical coatings with spatially non-uniform performance is presented. The setup allows spectral acquisition in the range of 400–1000 nm with spatial resolution higher than 20 µm. Examples of its implementation for the characterization of linearly variable optical components of portable spectrometers are given. OCIS codes: 120,0120. 310,0310. doi: 10.3788/COL201008S1.0103. Optical coatings for specific applications where an intentionally designed non-uniform surface induces spatially variable optical performance may have performance variations at a micrometer scale. To characterize the optical devices of this kind, a dedicated measurement technique is required to allow surface mapping of optical behavior. As long as commercial spectrophotometers have insufficient spatial resolution for acceptable results, dedicated apparatuses are needed for localized measurements. Recently, two instruments developed for localized photometry were compared [1] . In this letter, we present a novel setup with an extremely simplified construction for the purpose of transmittance measurement with enhanced spatial resolution and high spectral accuracy. Any type of structured material for which the transmittance is not constant over the surface can be measured by this apparatus, from biological samples to components for space applications. To illustrate the functionality of the proposed instrument, this study analyzes the optical performance of linearly variable filters manufactured in the frame of research programs for spatial applications. Such filters [2,3] are employed for the construction of miniaturized spectrometers for image spectroscopy of Earth and other planets from space. In particular, we report on the characterization of two different types of filters: an inducedtransmittance narrowband filter with linear variation of a transmittance peak over the surface and an all-dielectric low bandpass filter with nonlinear spatial profile. The filter transmission peak in the first case, as well as the edge of the pass-band in the second case, are moved from a minimum to a maximum wavelength (430–930 nm and 300–900 nm, respectively) over a spatial length of a few millimeters, with a gradient of about 200 nm/mm. The measurement setup (Fig. 1) consists of illuminating and collecting optics and a spectral analyzer connected to the computer. The radiation from a hybrid deuterium-tungsten source is delivered by an optical fiber with a 5 µm in-diameter core to the sample surface. The output fiber end is positioned at a distance of less that 1 mm from the sample to avoid scratching the fiber against the sample surface during the sample movement. At this distance, the numerical aperture of the illuminating fiber guarantees a light spot size less than 20 µm. The two-dimensional translation micrometric system insures accurate sample positioning for bi-dimensional scanning with a minimum motor step of 0.25 µm. A lens block focuses the transmitted light onto the entrance of a fiber with a 600 µm core, which is connected to the Ocean Optics HR2000 spectrometer. This spectrometer allows signal acquisition in the range of 300–1100 nm with a resolution of 2 nm. These range extremes are actually slightly shortened to 400–1000 nm due to a relatively high noise-to-signal ratio caused both by a low signal level (small core of illuminating fiber and non-optimized fiber-to-lamp connection) and a lower sensitivity of the spectrometer at the extremes of its working range. Both spectral range and spatial resolution may be improved if a spectrometer with an enhanced spectral resolution and sensitivity is employed or if the gap between the sample and the illuminating fiber is decreased. Both analyzed filters are multilayer optical coatings deposited on glass substrates. The first coating is comprises 21 alternating layers of silicon oxide and tantalum

Patterns of neurotransmitter receptor distributions following cortical spreading depression

Spreading depression (SD), a self-propagating depolarization of neurons and glia, is believed to play a role in different neurological disorders including migraine aura and acute brain ischaemia. Initiation and propagation of SD modulate excitability of neuronal network. A brief period of excitation heralds SD which is immediately followed first by prolonged nerve cell depression and later by an excitatory phase. The aim of the present study was to characterize local and remote transmitter receptor changes after propagation of cortical SD. Quantitative receptor autoradiography was used to asses 16 transmitter receptor types in combined striatum-hippocampus–cortex slices of the rat 1 h after induction of cortical SD. In neocortical tissues, local increases of glutamate NMDA, AMPA, and kainate receptor binding sites were observed. In addition to up-regulation of ionotropic glutamate receptors, receptor binding sites of GABAA, muscarinic M1 and M2, adrenergic α1 and α2, and serotonergic 5-HT2 receptors were increased in the hippocampus. Cortical SD also upregulated NMDA, AMPA, kainate, GABAA, serotonergic 5-HT2, adrenergic α2 and dopaminergic D1 receptor binding sites in the striatum. These findings indicate selective changes in several receptors binding sites both in cortical and subcortical regions by SD which may explain delayed excitatory phase after SD. Mapping of receptor changes by cortical SD increases our understanding of the mechanism of SD action in associated neurological disorders.

A Precision, Low-Cost GPS-Based Transmitter Synchronization Scheme for Improved AM Reception

This paper describes a highly accurate carrier-frequency synchronization scheme for actively, automatically locking multiple, remotely located AM broadcast transmitters to a common frequency/timing reference source such as GPS. The extremely tight frequency lock (to ~1 part in 109 or better) permits the effective elimination of audible and even sub-audible beats between the local (desired) station's carrier signal and the distant stations' carriers, usually received via skywave propagation during the evening and nighttime hours. These carrier-beat components cause annoying modulations of the desired station's audio at the receiver and concurrent distortion of the audio modulation from the distant station(s) and often cause listeners to ldquotune outrdquo due to the low reception quality. Significant reduction or elimination of the beats and related effects will greatly enlarge the effective (interference-limited) listening area of the desired station (from 4 to 10 times as indicated in our tests) and simultaneously reduce the corresponding interference of the local transmitter to the distant stations as well. In addition, AM stereo (CQUAM) reception will be particularly improved by minimizing the phase shifts induced by co-channel interfering signals; hybrid digital (HD) signals will also benefit via reduction in beats from analog signals. The automatic frequency-control hardware described is inexpensive ($1000-$2000), requires no periodic recalibration, has essentially zero long-term drift, and could employ alternate wide-area frequency references of suitable accuracy, including broadcasts from WWVB, LORAN-C, and equivalent sources. The basic configuration of the GPS-disciplined oscillator which solves this problem is extremely simple. The main oscillator is a conventional high-stability quartz-crystal type. To counter long- term drifts, the oscillator is slightly adjusted to track a high-precision source of standard frequency obtained from a specialized GPS receiver (or other source), usually at 10.000 MHz. This very stable local reference frequency is then used as a clock for a standard digitally implemented frequency synthesizer, which is programmed to generate the specific carrier frequency desired. The stability of the disciplining source, typically ~1 part in 109 to 1011, is thus transferred to the final AM transmitter carrier output frequency.

Photovoltaic performance of nanostructured zinc oxide sensitised with xanthene dyes

The photovoltaic properties of nanostructured ZnO electrodes prepared from commercially available ZnO nanoparticles (Degussa) and sensitised with xanthene dyes are explored. We have used Eosin Y, Eosin B and Mercurochrome and compared their performance to that of the more common N719 dye. We observe that these dyes efficiently sensitise commercial ZnO nanopowder and yield efficiencies that are very competitive with respect to those provided by N719. Local photocurrent and transmittance measurements as a function of the wavelength confirm the good performance of the xanthene dyes in the absorption maxima. We have prepared polymer-sealed cells and measured the short-circuit current of the devices under continuous illumination at 200 mW/cm 2 corresponding to twice the standard solar light intensity. The organic dyes show very good stability properties under these conditions. The combination of a versatile metal oxide such as ZnO and inexpensive organic dyes should be considered as a promising alternative in the field of dye-sensitised solar cells.

Preparation of one-dimensional photonic crystals by sol–gel process for magneto-optical materials

One-dimensional photonic crystal (PC) of periodically alternating low (SiO 2) and high (TiO 2) refractive index materials was prepared by sol–gel dip coating method that controls the thickness of each layer with nanometer level. The photonic band gap of high reflectivity was verified at wavelengths between 590 nm and 820 nm, which became significant with increasing the number of bilayer. The UV–vis spectra, SEM image and glow discharge optical emission spectroscopy indicate the periodic structure of SiO 2/TiO 2 multilayer. The magnetic layer of CoFe 2O 4 was also prepared by a sol–gel dip coating method. After the annealing at 700 °C, the single phase of CoFe 2O 4 film with spinel structure, without any preferred crystalline orientation, was obtained. In addition, the one-dimensional magnetophotonic crystal (MPC), in which the magnetic defect layer of CoFe 2O 4 is introduced into the periodic structure, was prepared. The light was localized at the magnetic defect due to the interference of the multilayer film, and the localized transmittance was observed around 530 nm. The Faraday rotation of MPC shows a peak at ∼ 570 nm which is close to the localized peak of transmittance. This may correspond to the enhancement of Faraday rotation due to the localization of light.

초음파 펄스 서모그라피를 이용한 세라믹 전열 판의 결함 검출

The applicability of UPT (Ultrasound Pulse Thermography) for real-time defect detection of the ceramic heating plate is described. The ceramic heating plate with superior insulation and high radiation is used to control the water temperature in underwater environment. The underwater temperature control system can be damaged owing to the short circuit, which resulted from the defect of the ceramic heating plate. A high power ultrasonic energy with pulse duration of 280 ms was injected into the ceramic heating plate in the vertical direction. The ultrasound excited vibration energy sent into the component propagate inside the sample until they were converted to the heat in the vicinity of the defect. Therefore, an injection of the ultrasound pulse wave which results in heat generation, turns the defect into a local thermal wave transmitter. Its local emission is monitored and recorded via the thermal infrared camera at the surface which is processed by image recording system. Measurements were performed on 4 kinds of samples, composed of 3 intact plates and the defect plate. The observed thermal image revealed two area of crack in the defective ceramic heating plate.

Dedicated spectrophotometer for localized transmittance and reflectance measurements

A dedicated spectrophotometer is built to achieve localized transmittance and reflectance measurements. The spatial resolution can be chosen from 100 microm to 2 mm, the spectral resolution from 0.5 to 5 nm, and the spectral range from 400 to 1700 nm. This apparatus can be used to study the index and thickness uniformity on single layers to determine and optimize the characteristics of the deposition chamber. It can also be used to measure the spatial variations of optical properties of intended nonuniform coatings such as linear variable filters.

Some characteristics of the electromagnetic field from radio transmitters in Europe

The radiomagnetotelluric (RMT) method utilizes man-made signals generated by distant transmitters or by dedicated local transmitters. Man-made electromagnetic (EM) signals in the [Formula: see text] frequency band come mainly from two sources: (1) distant radio transmitters operating in the [Formula: see text] band and (2) nearby or distant industrial sources emitting either transients or higher harmonics of [Formula: see text]. The natural or background EM signals form a kind of noise floor. In Europe for the [Formula: see text] band, there generally are sufficient transmitters available to estimate the EM transfer functions completely, i.e., the full impedance tensor and the tipper vector. We show examples of the variability of power spectra and azimuthal distributions of transmitters from sites in Sweden, Hungary, The Netherlands, and Spain. We also show that the estimated transfer functions are stable as a function of time; even under typical noisy conditions, simple stacking of spectra in narrow frequency bands provides good-quality estimates of transfer functions.

High accuracy measurement of the residual air gap thickness of thin-film and solid-spaced filters assembled by optical contacting

Optical contacting is a powerful tool for assembling solid-spaced filters in order to form a wavelength division multiplexing (WDM) multiple-cavity filter. In this article, we propose a method able to characterize the optical quality of such assembling with a high accuracy. We use localized spectral transmittance measurements to map the thickness of the residual air gap existing at the adhesion interface with a few nanometers precision. Tests on thick (2mm) and thin (100μm) substrates coated by Dual Ion Beam Sputtering are performed. Thus, we show that our 25mm-diameter samples are strictly contacted over more than 80% of their surface, with no detectable residual air gap.

On the RF/DSP design for efficiency of OFDM transmitters

In this paper, a system-level RF/digital signal processing (DSP) design approach of power-efficient orthogonal frequency-division multiplexing (OFDM) transmitters is proposed. A DSP-based low-IF architecture, which allows a significant enhancement of their power and spectrum efficiencies, is proposed. The cascade of the peak-to-average power ratio (PAPR) reduction technique, predistortion technique, and the in-phase and quadrature modulation led to impressive improvement in the power efficiency and effective linear output power of the OFDM transmitter. Measurement results carried out on an IEEE 802.11a transmitter designed and built for this experiment are presented in terms of error vector magnitude (EVM), adjacent channel leakage ratio, and power efficiency. The power stage of this transmitter uses a heterojunction bipolar InGaP transistor operating in a deeply class AB. The cascade of the PAPR reduction and baseband predistortion processing modules results in the reduction of the power backoff operation point by approximately 10 dB accompanied by a relative increase in the wireless local area network transmitter power efficiency by roughly 400% while meeting the emission mask spectrum and EVM levels demanded by the 802.11a standard.

Phase-domain all-digital phase-locked loop

A fully digital frequency synthesizer for RF wireless applications has recently been proposed. At its foundation lies a digitally controlled oscillator that deliberately avoids any analog tuning controls. When implemented in a digital deep-submicrometer CMOS process, the proposed architecture appears more advantageous over conventional charge-pump-based phase-locked loops (PLLs), since it exploits signal processing capabilities of digital circuits and avoids relying on the fine voltage resolution of analog circuits. An actual implementation of an all-digital PLL (ADPLL)-based local oscillator and transmitter used in a commercial 0.13-/spl mu/m CMOS single-chip Bluetooth radio has recently been disclosed. The conventional phase/frequency detector, charge pump and RC loop filter are replaced by a time-to-digital converter and a simple digital loop filter. Due to the lack of the correlational phase detection mechanism, the loop does not contribute to the reference spurs. The measured close-in phase noise of -86 dBc/Hz is adequate even for Global System for Mobile communications (GSM) applications. In this paper, we present the mathematical description and operational details of the phase-domain ADPLL.

Glutamate-regulated Behavior, Transmitter Release, Gene Expression and Addictive Plasticity in the Striatum: Roles of Metabotropic Glutamate Receptors

Metabotropic glutamate receptors (mGluRs) are G-protein-coupled receptors and are densely expressed in medium spiny projection neurons of striatum. Emerging evidence demonstrates a significant role of mGluRs in the regulation of striatal functions. Activation of mGluRs alters local transmitter release and behaviors of experimental animals. In particular, mGluRs regulate phosphorylation of several key signaling proteins (protein kinases and transcription factors) resulting in significant changes in immediate early gene and neuropeptide gene expression in striatal neurons. The prominent involvement of mGluRs in genomic responses to synaptic stimulation is considered to play a pivotal role in the development of synaptic/neuronal plasticity underlying long-term adaptive changes in cellular physiology related to a variety of neurologic disorders. Available data indicate that the eight subtypes of mGluRs have distinct effects on gene expression. The group I subtypes (mGluR1/5) facilitate, whereas group II (mGluR2/3) and III (mGluR4/6/7/8) subtypes inhibit, gene expression. Due to their significance in regulating drug action, mGluRs have been considered as promising targets for the development of novel therapeutic drugs for the treatment of drug addiction. The present review summarizes the roles of mGluRs in the regulation of behavior, transmitter release and particularly genomic responses in striatal neurons to dopamine stimulation, following a description of anatomical organization of mGluRs in the striatum. The possible pre- and postsynaptic mechanisms that process mGluR modulatory effects are also discussed in detail. Finally, potential of mGluRs as targets for the development of therapeutic drugs for addictive and other mental illnesses concludes this review.

New in vivo animal model to create intervertebral disc degeneration and to investigate the effects of therapeutic strategies to stimulate disc regeneration.

A new rabbit model was developed that produces disc degeneration through the application of controlled and quantified axial mechanical load. To characterize the changes associated with disc degeneration, and to evaluate the feasibility of local transfer of agents to the compressed discs to stimulate disc regeneration. Studies have shown that accelerated degeneration of the intervertebral disc results from altered mechanical loading conditions. The development of methods for the prevention of disc degeneration and the restoration of disc tissue that has already degenerated is needed. New Zealand white rabbits (n = 33) were used for this study. The discs in five animals remained unloaded and served as controls, whereas in 28 animals the discs were axially compressed using a custom-made external loading device. After 1 (n = 7), 14 (n = 7), and 28 (n = 7) days of dynamic loading, or 28 (n = 7) days of loading followed by 28 days of unloaded recovery time, the animals were killed and the lumbar spine was harvested for tissue preparation. Disc height, disc morphology, cell viability, disc stiffness, and load to failure were measured. Recombinant adenovirus encoding for two different marker genes (Ad-Luciferase and Ad-LacZ) was injected into the discs in loaded specimens and the gene expression was measured. The unloaded intervertebral discs of the rabbits consisted of a layered anulus fibrosus, a cartilaginous endplate, and a nucleus pulposus comparable with those of humans. After 14 and 28 days of loading, the discs demonstrated a significant decrease in disc space. Histologically, disorganization of the architecture of the anulus occurred. The number of dead cells increased significantly in the anulus and cartilage endplate. These changes were not reversible after 28 days of unloading. The stiffness and the load to failure did not change significantly in the discs after 28 days of loading, as compared with the unloaded control discs. Adenovirus-mediated gene transfer to discs was tolerated by all the animals. LacZ gene expression was found 2 weeks after injection of AdLacZ in loaded disc cells. The results of this study suggest that disc degeneration can be induced by axial dynamic loading in the rabbit intervertebral disc. The compressed rabbit intervertebral discs were large enough for the application of local transmitters through a percutaneous approach. We anticipate that this animal model could be used as a basic model to study intervertebral disc degeneration and to investigate new local therapeutic strategies for maintaining disc health or initiating tissue repair.