A System for Unsteady Pressure Measurements Revisited

An overview is presented of some recent developments in the field of the design of effective sound absorbers. The first part deals with the application of socalled coupled tubes. For this purpose use is made of a system originally applied for unsteady pressure measurements on oscillating wind tunnel models. The second part deals with an extension of the theory of tubing systems to thin air layers, trapped between flexible walls

Loline Alkaloid Gene Clusters of the Fungal Endophyte Neotyphodium Uncinatum

Loline alkaloids (LA), which are 1-aminopyrrolizidines with an oxygen bridge, are produced by Epichloë (anamorph=Neotyphodium) species, endophytes of grasses. LA are insecticidal, thus helping protect host plants from insect herbivory. Suppression subtractive hybridization PCR was used to isolate transcripts up-regulated during loline alkaloid production in cultures of Neotyphodium uncinatum. Subtracted cDNAs were cloned, and a λ-phage cDNA library from an LA-expressing N. uncinatum culture was screened with subtracted cDNA. In BLAST searches, several cDNAs identified had sequence similarities to aspartate kinases, and another with O-acetylhomoserine-(thiol)lyase. Differential expression of these two genes in LA-producing cultures of N. uncinatum was confirmed, and in a survey of 23 isolates from 21 Neotyphodium and Epichloë species these two genes strictly correlated with LA production. Two nucleic acid molecules encoding two loline alkaloid gene clusters have been identified

Air loads on a rigid plate oscillating normal to a fixed surface

This paper deals with the theoretical and experimental investigation on a rigid, rectangular plate oscillating in the proximity of a fixed surface. The plate is suspended by springs. The airloads generated by the oscillating motion of the plate are determined. Due to the fact that the plate is rigid, the system is modelled as a 1-DOF system. The influence of the surrounding air is detected by changes in the plate's natural frequency and damping. For the behaviour of the air in the gap between the plate and the fixed surface an analytical solution is presented. This solution includes the effects of inertia, viscosity, compressibility and thermal conductivity. It is shown that the main parameters governing the motion of the air in the gap are the shear wave number, the reduced frequency, the narrowness of the gap and the aspect ratio of the plate. With these parameters the validity of several simplifications can easily be demonstrated and solutions, given in the literature, can be put in perspective. Special experiments were carried out with an oscillating solar panel in order to verify the analytical model. The analytical results and the experimental results show fair agreement. The solutions shows that for low shear wave numbers the effects of viscosity cannot be discarded. \u

Gneiss-charnockite transformation at Kottavattam, Southern Kerala (India)

At Kottavattam, leucocratic granitic garnet-biotite gneisses (age less than 2 Ga) were partially transformed to coarse-grained charnockite along a system of conjugate fractures (N70E and N20W) and the foliation planes (N60 to 80W; dip 80 to 90 SW) about 550 m.y. ago. To examine and quantify changes in fabric, mineralogy, pore fluids and chemical composition associated with this process, large rock specimens showing gneiss-charnockite transition were studied in detail. The results of the present study corroborate the concept that charnockite formation at Kottavattam is an internally-generated phenomenon and was not triggered by the influx of carbonic fluids from a deep-seated source. It is suggested that charnockitization was caused by the following mechanism: (1) near-isothermal decompression during uplift of the gneiss complex led to an increase of the pore fluid pressure (P sub fluid greater than P sub lith) which - in a regime of anisotropic stress - triggered or at least promoted the development of conjugate fractures; (2) the simultaneous release of pore fluids from bursting fluid inclusions and their escape into the developing fracture system resulted in a drop of fluid pressure; and (3) the internal generation and buffering of the fluids and their, probably, limited migration in an entirely granitic rock system explains the absence of any significant metasomatic mass transfer

Baroreflex Amplification and Carotid Body Modulation for the Treatment of Resistant Hypertension

PURPOSE OF REVIEW: Patients with true resistant hypertension (RH) are characterized by having high sympathetic activity and therefore potentially benefit from treatments such as baroreflex amplification (baroreflex activation therapy (BAT) or endovascular baroreflex amplification therapy (EVBA)) or carotid body (CB) modulation. This review aims at providing an up-to-date overview of the available evidence regarding these two therapies. RECENT FINDINGS: In recent years, increasing evidence has confirmed the potential of baroreflex amplification, either electrically (Barostim neo) or mechanically (MobiusHD), to improve blood pressure control on short- and long-term with only few side effects, in patients with RH. Two studies regarding unilateral CB resection did not show a significant change in blood pressure. Only limited studies regarding CB modulation showed promising results for transvenous CB ablation, but not for unilateral CB resection. Despite promising results from mostly uncontrolled studies, more evidence regarding the safety and efficacy from ongoing large randomized sham-controlled trials is needed before baroreflex amplification and CB modulation can be implemented in routine clinical practice