Blood lead levels in pregnant women and the neonate

Population studies carried out during the 1980s had shown that the Maltese population was characterized by high blood lead (PbB) levels. These high levels appeared to be a feature at all age groups including neonates. A number of environmental control measures had been initiated to attempt to decrease these PbB levels. The present study reviews PbB levels in pregnant women and newborns. It is shown that mean cord PbB levels decreased significantly in the last decade from a mean of 165.1 + 87.9 ug/I in 1985 to 89.79 + 31.23 ug/I in 1996. This decrease did not correlate with the increasing use of multimineral supplements which include the zinc cation said to be useful to counter the effects of chronic lead intoxication. Placental transfer of lead is also shown to follow closely maternal levels with a correlation coefficient of 0.81. In spite of the apparent decrease in PbB levels, about half of newborns still I have levels which require preventive community measures.peer-reviewe

On some alien terrestrial and freshwater gastropods (Mollusca) from Malta

Nine species of gastropod molluscs: Otala lactea (0. F. MUller, 1774); Cemuella virgata (da Costa, 1778); Cochlicella barbara (Linnaeus, 1758); Oxychilus helveticus (Blum, 1881); Succinea putris (Linnaeus, 1758); Oxyloma elegans (Risso, 1826); Helisoma duryi Wetherby, 1879; Planorbarius comeus (Linnaeus, 1758); and the limacid slug Lehmannia valentiana (A. Ferussac, 1822) are recorded for the first time as alien species from local plant nurseries. For each species a short description and notes on distribution and ecology are given.peer-reviewe

On the introduction of Paranthrene tabaniformis (Rottemburg, 1775) in Malta (Insecta : Lepidoptera : Sesiidae)

The introduction of Paranthrene tabaniformis (Rottemburg) in· the Maltese Islands, an insect that is mainly associated with poplar trees (Populus sp.), is documented. Brief information is provided on the moth family Sesiidae with particular reference to the biology of P. tabaniformis. A brief overview of Maltese Sesiidae is included; previous records of Bembecia scopigera (Scopoli) were found to be incorrect as this material is B. albanensis tunetana (Le Cerf).peer-reviewe

A review of studies investigating the dielectric properties of biological tissues for application in hyperthermia and microwave thermal ablation

Heating of biological tissues beyond 40 C has become an established method of treating a number of diseases, most notably tumours, where hyperthermia and thermal ablation are important modalities. In some interventions, tissue temperatures reached can even go beyond 100 C, and demand precise knowledge of tissue dielectric properties and how these vary with frequency and temperature in order to facilitate accurate computational simulations for preclinical planning. This paper reviews the available literature concerning dielectric properties of biological tissues and their temperature dependence, focusing on the frequencies of 915 MHz and 2.45 GHz, at which most of the studies reviewed investigate predominantly liver tissue. In this review a comparative analysis of the results obtained by different research groups are presented in the different studies is also made, indicating possible limiting factors in the different studies. These studies propose a number of different models which could be used to describe temperature dependence. Due to the prevalence of liver investigations, it would be ideal to conduct further studies on different biological tissues.peer-reviewe

Report on the radiometric analysis of the Ghar Dalam fossil specimens prepared for the Ghar Dalam Museum

Uranium is a radioactive element emitting mainly alpha rays, but its daughter elements Th and Ra are gamma ray emitters. A high resolution gamma ray spectrometry system can be used to determine gamma-emitting radionuclides with energies ranging from 1 keV to 10 MeV depending on the type of detector in a large variety of sample matrices. The simultaneous detection of several gamma radionuclide emitters in the sample material was carried out with a coaxial germanium detector of high resolution connected to a multichannel analyser. Automatic processing of the collected spectral data was controlled by a computer system with selected software. Sources of error in the technique may be caused by improper spectral identities, changes in background, errors in calibration and/or geometry, and lack of homogeneity in samples. Since the samples tested were not in a standardised geometry, some variation in the readings could be expected due to the difference in sample homogeneity. The results obtained for the various samples were standardised as a ratio of 40K, on the assumption that the high solubility of potassium salts would result in a steady equilibrium in all samples. Several fossil specimens kept in the Ghar Dalam Museum were borrowed by courtesy of Dr. G. Zammit Maempel. The specimens had unfortunately no information as to the level they were excavated from, and their providence could not be reliably confirmed.peer-reviewe

In situ assessment of the setting of tricalcium silicate–based sealers using a Dentin pressure model

Introduction EndoSequence BC Sealer (Brasseler, Savannah, GA) is a premixed tricalcium silicate–based root canal sealer that requires moisture from the root dentin to hydrate. The aim of this study was to investigate the setting of EndoSequence BC Sealer and other sealers in contact with human dentin in a simulated clinical environment. Methods EndoSequence BC Sealer, MTA Fillapex (Angelus, Londrina, Brazil), Septodont Sealer (Septodont, Saint Maur-des-Fosses, France), and Apexit Plus (Ivoclar, Schaan, Lichtenstein) were assessed. Caries-free lower premolars extracted for orthodontic purposes in patients aged 13–16 years were standardized to a 10-mm root length and were filled with test sealers and set up in a dentin pressure model for 14 days. In addition, set sealers immersed in physiologic solution for 14 days were also assessed. The set materials in solution and materials retrieved from the dentin pressure setup were characterized by scanning electron microscopy and X-ray diffraction analysis. The setting time and radiopacity were assessed using ISO 6876:2002 specifications. Furthermore, mineral ion leaching was evaluated by inductively coupled plasma mass spectrometry. Results All the sealers tested exhibited formation of a calcium phosphate phase when in contact with physiologic solution. Septodont Sealer and Apexit Plus did not exhibit the formation of a calcium phosphate phase in the dentin pressure setup. The fluid in the system was enough to allow the setting of EndoSequence BC Sealer, which did not set in a dry environment. All materials leached calcium with the Septodont Sealer, exhibiting double the calcium ion leaching compared with EndoSequence BC Sealer. Conclusions Using the dentinal fluid pressure system resulted in an adequate flow of dentinal fluid that allowed EndoSequence BC Sealer to set inside the root canal. Although the sealers tested were tricalcium silicate based, the hydration reaction and bioactivity in the presence of dentinal fluid were different to hydration in vitro. Thus, clinically, material bioactivity cannot be assumed.peer-reviewe

Design and simulation of a 600 GHz RTD oscillator using commercial harmonic balance software

We report on the design and optimisation of a 600 GHz double barrier resonant tunneling diode (RTD) oscillator. Using the simple Esaki equivalent circuit diode model and published DC experimental I-V data, a custom device model was developed and integrated within a commercial harmonic balance (HB) simulator. This technique utilizes a spline interpolation algorithm as part of the device model to determine instantaneous values of device voltage and current when called from within the main HB software. The maximum oscillation frequency for a 5 ohms load was 1.6 THz, whilst optimisation at 600 GHz was achieved with a 15 ohms load, with an output power of 420 micron W. The present technique should facilitate and simplify simulation of both existent and novel non-linear devices in other configurations, such as multipliers, mixers, self- oscillating mixers, etc.peer-reviewe

Back trauma resulting in commotio cordis

Commotio cordis (Latin: "agitation of the heart") is a dysrhythmia provoked by praecordial trauma during the early part of cardiac repolarisation. Recorded rhythms include ventricular tachycardia/fibrillation, bradyarrhythmias, idioventricular rhythm, complete heart block and asystole. The quoted fatality rate is 65% even with prompt CPR and defibrillation, and exceeds 80% in the absence of such interventions. Above a certain threshold of trauma/impact, structural cardiac damage may also occur (contusio cordis).peer-reviewe

Application of artificial neural networks for accurate determination of the complex permittivity of biological tissue

Medical devices making use of radio frequency (RF) and microwave (MW) fields have been studied as alternatives to existing diagnostic and therapeutic modalities since they offer several advantages. However, the lack of accurate knowledge of the complex permittivity of different biological tissues continues to hinder progress in of these technologies. The most convenient and popular measurement method used to determine the complex permittivity of biological tissues is the open-ended coaxial line, in combination with a vector network analyser (VNA) to measure the reflection coefficient (S11) which is then converted to the corresponding tissue permittivity using either full-wave analysis or through the use of equivalent circuit models. This paper proposes an innovative method of using artificial neural networks (ANN) to convert measured S11 to tissue permittivity, circumventing the requirement of extending the VNA measurement plane to the coaxial line open end. The conventional three-step calibration technique used with coaxial open-ended probes lacks repeatability, unless applied with extreme care by experienced persons, and is not adaptable to alternative sensor antenna configurations necessitated by many potential diagnostic and monitoring applications. The method being proposed does not require calibration at the tip of the probe, thus simplifying the measurement procedure while allowing arbitrary sensor design, and was experimentally validated using S11 measurements and the corresponding complex permittivity of 60 standard liquid and 42 porcine tissue samples. Following ANN training, validation and testing, we obtained a prediction accuracy of 5% for the complex permittivity.peer-reviewe

A numerical investigation of the dispersion law of materials by means of multi-length TDR data

In this paper, we propose a method for retrieving the dispersion law of a material under test from multi-length TDR measurements in reflection mode, repeated at several frequencies. By replacing the multi-frequency measurements with measurements using multi-length TDR probe, it is possible to retrieve the complex equivalent permittivity of the material in a frequency band of interest. The proposed procedure does not require a priori knowledge of the type of dispersion law of the material, which instead can possibly be inferred from the measured data. The algorithm is validated using numerically simulated data obtained with the commercial code CST Microstudio®.peer-reviewe