A new in situ test for the assessment of the rock-burst alarm threshold during tunnelling

Rock-burst is one of the most serious risks associated with hard rock tunnelling and mining at high depths. Monitoring of acoustic emissions emitted by the rock-mass during excavation and their interpretation now permits the early assessment of failure events and makes the safe management of the construction works possible. A reliable set-up of the alarm threshold is thus fundamental for the correct implementation of the procedures planned to minimise rock-burst related risk. This paper focuses on a novel in situ test specifically developed to provide an experimental basis for a more accurate assessment of the alarm threshold during tunnelling, representative of the local geomechanical conditions. The test, thanks to the compression induced by two flat jacks at the tunnel side wall, produces an artificial failure process during which acoustic emissions are measured and correlated to the mechanical response of the rock-mass, without the typical limitations of scale that characterised the laboratory experiments. The new methodology, named the Mules method, was successfully tested during the excavation of some stretches of the Brenner Base Tunnel in the Brixner granite, affected by mild spalling episodes. The case-history is fully described in the paper to illustrate the practical application of the proposed approach

Glycoengineered outer membrane vesicles: A novel platform for bacterial vaccines

The World Health Organization has indicated that we are entering into a post-antibiotic era in which infections that were routinely and successfully treated with antibiotics can now be lethal due to the global dissemination of multidrug resistant strains. Conjugate vaccines are an effective way to create a long-lasting immune response against bacteria. However, these vaccines present many drawbacks such as slow development, high price, and batch-to-batch inconsistencies. Alternate approaches for vaccine development are urgently needed. Here we present a new vaccine consisting of glycoengineered outer membrane vesicles (geOMVs). This platform exploits the fact that the initial steps in the biosynthesis of most bacterial glycans are similar. Therefore, it is possible to easily engineer non-pathogenic Escherichia coli lab strains to produce geOMVs displaying the glycan of the pathogen of interest. In this work we demonstrate the versatility of this platform by showing the efficacy of geOMVs as vaccines against Streptococcus pneumoniae in mice, and against Campylobacter jejuni in chicken. This cost-effective platform could be employed to generate vaccines to prevent infections caused by a wide variety of microbial agents in human and animals

Chronic migraine plus medication overuse headache: two entities or not?

Chronic migraine (CM) represents migraine natural evolution from its episodic form. It is realized through a chronicization phase that may require months or years and varies from patient to patient. The transition to more frequent attacks pattern is influenced by lifestyle, life events, comorbid conditions and personal genetic terrain, and it often leads to acute drugs overuse. Medication overuse headache (MOH) may complicate every type of headache and all the drugs employed for headache treatment can cause MOH. The first step in the management of CM complicated by medication overuse must be the withdrawal of the overused drugs and a detoxification treatment. The goal is not only to detoxify the patient and stop the chronic headache but also to improve responsiveness to acute or prophylactic drugs. Different methods have been suggested: gradual or abrupt withdrawal; home treatment, hospitalization, or a day-hospital setting; re-prophylaxes performed immediately or at the end of the wash-out period. Up to now, only topiramate and local injection of onabotulinumtoxinA have shown efficacy as therapeutic agents for re-prophylaxis after detoxification in patients with CM with and without medication overuse. Although the two treatments showed similar efficacy, onabotulinumtoxinA is associated with a better adverse events profile. Recently, the Phase III Research Evaluating Migraine Prophylaxis Therapy (PREEMPT) clinical program proved that patients with CM, even those with MOH, are the ones most likely to benefit from onabotulinumtoxinA treatment. Furthermore, it provided an injection paradigm that can be used as a guide for a correct administration of onabotulinumtoxinA

Rock-burst risk assessment by acoustic emission measurement and interpretation at the Brenner Base Tunnel. The “Mules method”

The paper describes the experience gained during the excavation of some stretches of the Brenner Base Tunnel system, a complex underground network for the connection of the city of Fortezza, in Italy, to the city of Innsbruck, in Austria, in the framework of the Scandinavian Mediterranean corridor 5 of the Trans European Network-Transport. The occurrence of some rock-burst phenomena, although of mild intensity, during drill-and-blast tunnelling in the Brixner granite formation at depths over 1000 m has promoted the implementation of efficient and accurate strategies for the early assessment of risk and for its management. A comprehensive procedure, named the Mules method, has been developed and successfully applied long all the tunnel segments at risk. This approach, based on the combination of the continuous monitoring of acoustic emissions near the tunnel face and a newly developed in situ test for the experimental validation of the alarm threshold, can be considered of general validity and potentially exportable to other construction sites

A standard procedure for rock-burst prediction during tunnel construction. The “Mules method”

Rock-burst phenomena occur frequently during the excavation of deep tunnels in good-quality rock-mass. This paper describes the procedure developed and successfully applied during the excavation of the Brenner Base Tunnel in the Brixner granite formation for the early detection of rock-burst related risk. It consists in the continuous monitoring of acoustic emissions and in their comparison with an alarm threshold calibrated on specifically designed in situ tests. During the in situ test the rock-mass is brought to failure by the compression applied by two flat jacks at the tunnel wall while the related acoustic emissions are simultaneously measured by a system of accelerometric sensors, whose records are interpreted in terms of power spectrum density. Two in situ tests were carried out providing consistent results despite varying geomechanical conditions, also highlighted by the results of uniaxial compression tests performed in the laboratory. The procedure has been validated over the last three years and has proved its reliability in the reduction of risk

Emicrania, FOP e alterazioni RMN

L\u2019emicrania e lo shunt dx/sn da forame ovale pervio (FOP) sono considerati fattori di rischio per lo stroke ischemico giovanile (Lechat, et al., 1988, Webster at al., 1988, Ditullio et al., 1992). Dati recenti suggeriscono che, come per lo stroke giovanile, in una percentuale pari al 40% di emicranici con aura (ECA) \ue8 dimostrabile una perviet\ue0 del forame ovale (Del Sette et al., 1998, Anzola et al., 1999), il che induce a supporne un possibile ruolo concausale dell\u2019emicrania (Sztajzel et al., 2002). Inoltre in un nostro precedente studio era stata rilevata una maggior frequenza di lesioni della sostanza bianca alla RMN negli emicranici con FOP (Giberti et al., 2002) .Scopo dello studio, oltre alla conferma di questi risultati, \ue8 quello di correlare le caratteristiche dell\u2019emicrania (presenza/assenza di aura; alta/bassa frequenza degli episodi) con i reperti RMN e la presenza e tipo di FOP. Sono stati arruolati 63 pazienti emicranici, 32 ECA e 31 senz\u2019aura (ESA), privi di fattori di rischio cerebrovascolare, di et\ue0 media 36 anni - \uf073 = 5.89, durata di malattia uniforme (media 8 anni - \uf073 = 1.5), considerando la frequenza delle crisi, la presenza di shunt dx/sn (rilevata con doppler transcranico e confermata dall\u2019ecocardiografia transesofagea) e la presenza di lesioni iperintense della sostanza bianca alla RMN. La distribuzione del tipo di FOP \ue8 significativamente (p = 3.6 * 10^-5) diversa nei pazienti con ECA rispetto a quelli con ESA, indipendentemente dalla frequenza delle crisi (p = 0.21): i soggetti con ECA hanno infatti FOP permanente nel 34% dei casi e FOP latente nel 16%, mentre quelli con ESA hanno FOP permanente nel 10% e FOP latente nel 23% dei casi. Le alterazioni RMN sono a loro volta correlate in maniera pi\uf9 significativa con l\u2019alta frequenza delle crisi (66% di positivit\ue0 tra quelli con alta frequenza, 30% di positivit\ue0 nei casi con bassa frequenza; p = 3.6 * 10^-4) piuttosto che con il tipo di crisi (frequenza lievemente superiore nell\u2019ECA: 47%, rispetto all\u2019ESA: 39%). L\u2019associazione significativa fra FOP permanente e ECA suggerisce un possibile ruolo patogenetico dello shunt nel determinismo della crisi con aura, con meccanismi ancora ipotetici (D\u2019Andrea et al., 1985, Wilmshurst et al., 2000, Pierangeli et al., 2002). Resta da dimostrare il significato delle lesioni alla RM nel follow-up a lungo termine dei pazienti con alta frequenza di crisi, in particolare per quanto concerne l\u2019eventuale sviluppo di disabilit\ue0 neurologic

A new methodology for the rock-burst assessment during tunnel construction

Risk associated to rock-burst occurrence in tunnels is nowadays managed by a continuous monitoring of acoustic emissions recorded during the excavation, whose characteristics depend on the failure processes ongoing in the rock-mass. A new in situ test was specifically designed with the aim of calibrating the alarm threshold for rock-burst occurrence. The test consists in compressing to failure a portion of the rock-mass at the tunnel side-wall by means of a couple of flat-jacks, measuring simultaneously the generated acoustic emissions with accelerometers. The test was for the first time carried out at the Brenner Base Tunnel in massive granite below an overburden of about 1200 m, nearby tunnel locations affected in the past by few mild rock-burst phenomena. Recorded data clearly indicated that a correlation exists between the energy and frequency content of the acoustic emissions and the rock-mass failure. Following the experimental investigation, and consistently with the available monitoring evidence, a new higher alarm threshold was implemented at the construction site. Further tests are currently in progress: These are aimed to validate the results and to produce a testing standard that may be applied to the construction of tunnels affected by rock-burst phenomena

Acoustic emissions from flat-jack test for rock-burst prediction

Rock-burst is a local instability problem affecting compact rock-masses in deep tunnels: it can generate important over-breaks, but even more, safety issues for workers in the area where it occurs. The experimental study, aimed at predicting rock-burst occurrence during the excavation of the Brenner Base Tunnel, was carried out in massive granite below an overburden of 1000-1200 m. The experiment consisted in compressing a portion of the rock-mass at the tun-nel side-wall by means of a couple of flat-jacks, measuring simultaneously the generated acoustic emissions with velocimeters and accelerometers. Recorded data clearly show a peak in the acoustic emission energy few instants before the failure of the rock-mass. This value, after careful site validation based on the continuous monitoring of acoustic emissions during the excavation, has been implemented as an alarm threshold for the interpretation of measurements and for the adoption of appropriate countermeasures

Acoustic emissions from flat-jack test for rock-burst prediction

Rock-burst is a local instability problem affecting compact rock-masses in deep tunnels: it can generate important over-breaks, but even more, safety issues for workers in the area where it occurs. The experimental study, aimed at predicting rock-burst occurrence during the excavation of the Brenner Base Tunnel, was carried out in massive granite below an overburden of 1000-1200 m. The experiment consisted in compressing a portion of the rock-mass at the tun-nel side-wall by means of a couple of flat-jacks, measuring simultaneously the generated acoustic emissions with velocimeters and accelerometers. Recorded data clearly show a peak in the acoustic emission energy few instants before the failure of the rock-mass. This value, after careful site validation based on the continuous monitoring of acoustic emissions during the excavation, has been implemented as an alarm threshold for the interpretation of measurements and for the adoption of appropriate countermeasures