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Genetic conditions, traumatic injuries, carious lesions and periodontal diseases are all responsible for dental pathologies. The current clinical approaches are based on the substitution of damaged dental tissues with inert materials, which, however, do not ensure full physiological recovery of the teeth. Different populations of dental mesenchymal stem cells have been isolated from dental tissues and several attempts have already been made at using these stem cells for the regeneration of human dental tissues. Despite encouraging progresses, dental regenerative therapies are very far from any clinical applications. This is tightly connected with the absence of proper platforms that would model and faithfully mimic human dental tissues in their complexity. Therefore, in the last decades, many efforts have been dedicated for the development of innovative systems capable of emulating human tooth physiology in vitro. This review focuses on the use of in vitro culture systems, such as bioreactors and “organ-on-a-chip” microfluidic devices, for the modelling of human dental tissues and their potential use for dental regeneration and drug testing.

The spontaneous spinal epidural haematoma (SSEH) is a rare emergency condition due to an accumulation of blood in the epidural space that can compress the spinal cord and can lead to severe neurological sequelae. The typical symptom of SSEH is severe back or neck pain, followed by symptoms and signs of spinal cord compression. A detailed history and an accurate neurologic examination are important tools for early diagnosis and magnetic resonance imaging (MRI) is currently the diagnostic method of choice. Performing a rapid decompressive surgery is very important in achieving positive clinical outcomes. The paper presents a case of a 12-year-old boy who developed severe abdominal pain and progressive weakness in his legs. MRI demonstrated an epidural mass extending from C3 through T1, causing spinal cord compression. Emergent decompressive laminectomy was performed. Optimal functional outcomes were obtained.

An international comparison of two I-2-stabilized frequency-doubled Nd:YAG lasers at lambda = 532 nm has been performed between the Istituto di Metrologia ``G. Colonnetti'' (IMGC)/Politecnico di Milano (PoliMI) and the Physikalisch-Technische Bundesanstalt (PTB). Both lasers used saturated absorption of the P(54) 32-0 iodine transition as a frequency reference. The signals for stabilizing the lasers were obtained using the frequency modulation spectroscopy technique with an external iodine cell. A minimum value for the relative Allan standard deviation of 7 x 10(-14) was reached after an integration time of 40 s. The hyperfine line separations were measured by the beat-frequency method and compared with the frequency values recently reported by Ye and co-workers. Three different iodine cells were investigated. The range of frequency differences for the iodine cells IMGC(QU) and PTB1/98 between the two lasers was from -9 kHz to 7.3 kHz with a mean of 1.2 kHz and a standard deviation of 3.5 kHz. Taking into account the measured frequency offsets of the different iodine cells, the evaluated frequency repeatability of the optical standards was within 2.5 kHz.

The paper is concerned with multilayer and fine thermal control of an optical reference cavity for space applications, under development at National Metrology Institute, Turin, Italy. The cavity, made by ultra low expansion glass (Corning ULEreg), must be kept close to the zero-expansion temperature (close to 25degC) of the glass. The target can only be met by active control, while leaving the cavity free of sensor and actuators. This is obtained by two concepts: thermal bath and reference thermal sink, the latter allowing zero-expansion temperature to be reached by heaters in a wide environment range. Preliminary experiments of the two concepts leading to cavity design are detailed.

The scapholunate ligament plays a vital role in normal physiological wrist kinematics. Rupture of this ligament is common and results in a dorsal intercalated segment instability (DISI) deformity that, if not corrected, progresses to a scapholunate advanced collapse (SLAC) wrist. Multiple treatment techniques have been proposed to address scapholunate dissociation such as indirect soft tissue repairs, autografts, allografts, and arthrodesis. Yet no single procedure has proven to be superior clinically or biomechanically for chronic DISI deformity. This study accurately assesses the degree to which three repair techniques, the Reverse Blatt’s Capsulodesis [1] (RBC), the Bone-Ligament-Bone autograft repair technique (BLB) and the Reduction and Association of the Scaphoid and Lunate (RASL), restore the normal physiologic scapho-lunate in vitro kinematics following a simulated scapholunate dissociation in a human cadaveric model.

The results of an international comparison between the He-Ne lasers stabilized to 127I2 at 633 nm of the IMGC (Istituto di Metrologia "G. Colonnetti", Turin, Italy) and the IFA-IFTAR (Institute of Atomic Physics-IFTAR, Department of Lasers, Bucharest, Romania) are reported. The mean frequency difference, considering the hyperfine structure components d, e, f and g of the R(127) 11-5 transition, was Δν = νRO.2 - νIMGCA4/5 = 3,8 kHz, standard uncertainty u = 5,7 kHz, or Δν/ν0 = 0,8 × 10-11, standard uncertainty u = 1,2 × 10-11. The frequency stability, expressed as the relative Allan standard deviation of the beat note between the two lasers, resulted 3,7 × 10-12 for a 100 s sampling time.

An interferometric force balance (Nanobalance) for space micro-thruster qualification is presented. A new generation of space micro-thrusters is under development aiming at thrust resolution and accuracy below one micronewton. Nanobalance has been conceived and developed for ground calibration of thrust time profile and noise with sub-micronewton accuracy.

Preliminary results on absolute frequency stabilization of Distributed Bragg Reflector (DBR) diode-lasers with emission wavelength at 852 nm will be reported. Saturated absorption D-2 lines of cesium atom have been adopted as a frequency reference and the non-linear spectroscopy method of Modulation Transfer has been used to lock the laser frequency against the resonance. From the preliminary results on the beat signal between two independent laser systems a relative frequency stability of 10(-11) has been reached at an integration time of 0.1 s. The analysis on the obtained signal to noise ratio shows a frequency noise floor in the order of approximate to 10(-12) which should be achieved in an integration time of I s.

Preliminary results of an international comparison between the He-Ne lasers stabilized to 127I2 at 633 nm of the Instituto di Metrologia G. Colonnetti (IMGC) and the Institute of Atomic Physics-IFTAR (IFA-IFTAR), Department of Lasers are reported. The mean frequency difference, considering the hyperfine structure components d, e, f and g, resulted as (Delta) (nu) equals (nu) IMGC4/5 - (nu) R0.2 equals (-3.8 +/- 5.7) kHz, or as relative value reported to the laser frequency as (Delta) (nu) /(nu) o equals (0.8 +/- 1.2) X 10-11. The frequency stability, expressed as the Allan variance of the beat note between the two lasers, resulted 3.65 X 10-12 for 100 s sampling time.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The stabilization of a He-Ne (Helium-Neon) laser to hyper-fine structure (HFS) components of the P(48) 11-3 transition of 127I2 at 612 nm observed in an external iodine cell, may give a frequency reproducibility of ±5 kHz or ±1 × 10-11·? and a stability of 1.4 × 1013·? for an observation time ? = 100 s. From 3He-22Ne lasers stabilized to HFS components of 127I2 observed in an intracavity cell, both at 612 and 640 nm wavelengths, a reproducibility of ±2 × 10-10· ? can be expected. Common and convenient operating conditions have been found at both wavelengths.

Two 127I 2 transitions coincident with the 20Ne emission at 605 nm have been identified. One of them is sufficiently intense for locking the laser frequency to one isolated hyperfine structure (HFS) component. The performances presently achieved are: a stability of 6 ∗ 10−13 ∗ ν for an integration time τ = 1000 s and a reproducibility of 200 kHz(4 ∗ 10−10 ∗ ν).

In November 1981, a comparison between BIPM and IMGC He-Ne lasers stabilized to saturated absorption lines of 127I2, at the wavelengths ? = 633 nm and ? = 612 nm has been made at the BIPM. At 633 nm, a repeatability and a reproducibility within +1 × 10-11 · ? have been obtained. At 612 nm, a repeatability within a few 10-11 · ? only for one laser and a reproducibility of ± 2 × 10-10 · ? have been obtained.