The cylindrical drift chamber is the most innovative part of the MEG II detector, the upgraded version of the MEG experiment. The MEG II chamber differs from the MEG one because it is a single volume ...cylindrical structure, instead of a segmented one, chosen to improve its resolutions and efficiency in detecting low energy positrons from muon decays at rest. In this paper, we show the characteristics and performances of this fundamental part of the MEG II apparatus and we discuss the impact of its higher resolution and efficiency on the sensitivity of the MEG II experiment. Because of its innovative structure and high quality resolution and efficiency the MEG II cylindrical drift chamber will be a cornerstone in the development of an ideal tracking detector for future positron-electron collider machines.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Mycobacterium chimaera is a recently described nontuberculous mycobacterium belonging to the Mycobacterium avium complex (MAC). Because this species is implicated in a worldwide outbreak due to ...contaminated heater–cooler unit water tanks during open-heart surgery, it has become mandatory for clinical microbiology laboratories to be able to differentiate M. chimaera from the other MAC species, especially M. intracellulare. Such identification has so far been restricted to specialized laboratories because it required the analysis of several gene sequences. The aim of this study was to evaluate commercial methods for identifying M. chimaera with regard to the reference gene sequencing ITS, the internal transcribed spacer 16–23S.
Forty-seven clinical and environmental isolates including 41 MAC were identified by (a) PCR sequencing of the ITS and hsp65 genes, (b) three molecular biology kits (INNO-LiPA Mycobacteria, GenoType Mycobacterium CM and GenoType NTM-DR) and (c) matrix-assisted desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) using Microflex LT.
There was a high concordance for species determination between the reference ITS sequencing and the GenoType NTM-DR test (39/41, 95%), the INNO-LiPA Mycobacteria test (38/41, 93%) and the hsp65 sequencing (38/41, 93%). The GenoType Mycobacterium CM test did not distinguish M. chimaera from M. intracellulare. MALDI-TOF MS distinguished two M. chimaera–M. intracellulare groups separated from M. avium and from the other mycobacterial species on a score-oriented dendrogram, but it also failed to differentiate the two species.
INNO-LiPA Mycobacteria and GenoType NTM-DR are efficient assays for M. chimaera identification in clinical microbiology laboratories.
Distinguishing between urinary tract infection (UTI) and asymptomatic bacteriuria (ABU) is difficult in the geriatric population since specific symptoms are often lacking. Escherichia coli is the ...most frequent UTI pathogen in this population but also a common urine colonizer. We hypothesized that detecting E. coli phylogroups B2 or D, which were previously associated with virulent strains responsible for extra-intestinal infections outside elderly patients, could help in distinguishing UTI from ABU.
Consecutive cases of E. coli bacteriuria diagnosed in hospitalized patients >75 years old during 3 months were investigated for E. coli phylogroups. Multiplex PCR was used to search for several virulence genes as previously described. Characteristics of UTI and ABU cases, assessed retrospectively according to definitions and geriatric expertise, were compared.
Out of 233 bacteriuria cases, 60 were assessed to be UTI and 163 to be ABU, with 10 cases unclassified. E. coli strains belonging to the phylogroups B2 and D were significantly more frequent in UTI (48/60, 80%) than in ABU (101/163, 62%) by univariate and multivariate analyses (OR 3.05, 1.44–6.86, p 0.005). Out of all the host and bacterial characteristics studied, falls (p 0.032), comorbidities (p 0.041), and altered autonomy evaluated by a low activity of daily living score (p 0.027) were also associated with UTI using univariate and multivariate analysis.
Determination of the E. coli phylogroup, in addition to some host characteristics, can help to distinguish UTI from ABU in elderly patients with bacteriuria. If this hypothesis is confirmed by prospective studies, then inappropriate use of antibiotics may be reduced in ABU cases.
This study compared standard of care testing (SOC) to BioFire® FilmArray® Pneumonia
plus
Panel (PN
plus
). PN
plus
detects 15 bacteria with semiquantitative log bin values, 7 antibiotic resistance ...markers, three atypical bacteria (AB), and eight viral classes directly from bronchoalveolar lavage-like specimens (BLS) and sputum-like specimens (SLS). Fifty-two laboratories from 13 European countries and Israel tested 1234 BLS and 1242 SLS with PN
plus
and SOC. Detection rates and number of pathogens/samples were compared for PN
plus
pathogens. PN
plus
bin values and SOC quantities were compared. Three thousand two hundred sixty-two bacteria in PN
plus
were detected by PN
plus
and/or SOC. SOC detected 57.1% compared to 95.8% for PN
plus
(
p
≤ 0.0001). PN
plus
semiquantitative bin values were less than SOC, equal to SOC, or greater than SOC in 5.1%, 25.4%, and 69.6% of results, respectively. PN
plus
bin values were on average ≥ 1 log than SOC values (58.5% 1–2 logs; 11.0% 3–4 logs). PN
plus
identified 98.2% of MRSA and SOC 55.6%. SOC detected 73/103 AB (70.9%) and 134/631 viruses (21.2%). PN
plus
detected 93/103 AB (90.3%) and 618/631 viruses (97.9%) (
p
≤ 0.0001). PN
plus
and SOC mean number of pathogens/samples were 1.99 and 1.44, respectively. All gram-negative resistance markers were detected. PN
plus
and SOC results were fully or partially concordant for 49.1% and 26.4% of specimens, respectively. PN
plus
was highly sensitive and detected more potential pneumonia pathogens than SOC. Semiquantification may assist in understanding pathogen significance. As PN
plus
generates results in approximately 1 h, PN
plus
has potential to direct antimicrobial therapy in near real time and improve antimicrobial stewardship and patient outcomes.
The MEG II experiment, based at the Paul Scherrer Institut in Switzerland, reports the result of a search for the decay
μ
+
→
e
+
γ
from data taken in the first physics run in 2021. No excess of ...events over the expected background is observed, yielding an upper limit on the branching ratio of
B
(
μ
+
→
e
+
γ
)
<
7.5
×
10
-
13
(90% CL). The combination of this result and the limit obtained by MEG gives
B
(
μ
+
→
e
+
γ
)
<
3.1
×
10
-
13
(90% CL), which is the most stringent limit to date. A ten-fold larger sample of data is being collected during the years 2022–2023, and data-taking will continue in the coming years.
Blood culturing (BC) remains the gold standard for bloodstream diagnosis but its workflow is slow. We aimed reducing this time by implementing a new automated incubator with a 24/7 BC workflow. With ...this new strategy, time to incubation was shorter (1.52 h vs 6.82 h), positivity rates were higher (10.6% vs 8.9%,
p<
0.05), and the number of BSI diagnostics increased (16.1% vs 13.8% patients and 2.3 vs 1.9 density episode per 1000 hospital days). Our results show that implementing automatic loading of BC bottles with a 24/7 strategy not only shortened time to diagnosis but significantly increased the BSI diagnosis rate.
The Cylindrical Drift Chamber of the MEG II experiment Chiappini, M.; Baldini, A.M.; Benmansour, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2023, Letnik:
1047
Journal Article
Recenzirano
The MEG experiment at the Paul Scherrer Institut (PSI) represents the state of the art in the search for the charged Lepton Flavor Violating μ+→e+γ decay, setting the most stringent upper limit on ...the BR (μ+→e+γ)≤4.2×10−13 (90% C.L.). An upgrade of MEG, MEG II, was designed, commissioned and recently started the physics data taking. Its goal is to reach a sensitivity level of 6×10−14. In order to reconstruct the positron momentum vector a Cylindrical Drift CHamber (CDCH) with unprecedented peculiarities was built, featuring angular and momentum resolutions at the 6.5 mrad and 100 keV/c level. The CDCH is a 2-meter long, 60 cm in diameter, low-mass, single volume detector with high granularity: 9 layers of 192 drift cells, few mm wide, defined by ∼12000 wires in a stereo configuration for longitudinal hit localization. The filling gas mixture is Helium:Isobutane 90:10. The total radiation length is 1.5×10−3 X0, thus minimizing the Multiple Coulomb Scattering and allowing for a single-hit resolution <120μm. After the assembly at INFN Pisa, the CDCH was transported to PSI and integrated into the MEG II experimental apparatus since 2018. The commissioning phase lasted for the past three years until the operational stability was reached in 2020. The analysis software is continuously developing and the tuning of the reconstruction algorithms is one of the main activities. The latest updates on the positron momentum vector resolutions and tracking efficiency are presented.
Operation and performance of the MEG II detector Afanaciev, K.; Baldini, A. M.; Ban, S. ...
The European physical journal. C, Particles and fields,
02/2024, Letnik:
84, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The MEG II experiment, located at the Paul Scherrer Institut (PSI) in Switzerland, is the successor to the MEG experiment, which completed data taking in 2013. MEG II started fully operational data ...taking in 2021, with the goal of improving the sensitivity of the
μ
+
→
e
+
γ
decay down to
∼
6
×
10
-
14
almost an order of magnitude better than the current limit. In this paper, we describe the operation and performance of the experiment and give a new estimate of its sensitivity versus data acquisition time.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
9.
Commissioning and preliminary performance of the MEG II drift chamber Chiappini, M.; Chiarello, G.; Baldini, A.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2022, Letnik:
1041
Journal Article
Recenzirano
In the quest for Lepton Flavor Violation (LFV) the MEG experiment at the Paul Scherrer Institut (PSI) represents the state of the art in the search for the charged LFV decay μ+→e+γ, setting the most ...stringent upper limit on the BR(μ+→e+γ)≤4.2×10−13 (90% C.L.). An upgrade of MEG, MEG II, was designed and it recently started the physics data taking, with the aim to reach a sensitivity level of 6×10−14. The Cylindrical Drift CHamber (CDCH) is a key detector in order to improve the e+ angular and momentum resolutions at the 6.5 mrad and 100 keV/c level. The CDCH is a low-mass single volume detector with high granularity: 9 layers of 192 drift cells each, few mm wide, defined by 12000 wires in a stereo configuration for longitudinal hit localization. After the assembly, the CDCH was transported to PSI for the commissioning phase and it has been integrated into the MEG II experimental apparatus since 2018. The operational stability was reached in 2020 and the complete readout electronics was tested for the first time in 2021. A preliminary analysis of 2020–2021 data is presented.
Blood culture (BC) efficiency is critical for the diagnosis of bloodstream infection (BSI). We evaluated the impact on standard care of implementing the new BacT/ALERT® FAPlus and FNPlus BC bottles ...containing antibiotic-binding polymeric beads. We measured positivity rates and time to detection (TTD) during the first 10 months of implementation (PF) and during the previous 10-month period (PS) during which we were using standard aerobic (SA) or standard anaerobic (SN) BC bottles. For each period, the same number of consecutive patients (
n
= 3,918) was included. Per patient, a median of 1 BC set (1 aerobic and 1 anaerobic bottles) has been sampled. A higher positivity rate was measured during PF than PS when counting per BC bottle (7.0 % vs 5.8 % with 1,456 and 1,237 positive bottles respectively,
P <
0.0001) and per BC set (9.6 % vs 7.8 % with 995 and 832 positive BC sets respectively,
P
< 0.0001). In PF, an increased number of cases due to staphylococci (
P
< 0.0001) and to Gram-negative bacilli (
P
< 0.005) was observed, whereas the contamination rate was similar during the two periods (2.4 % of BC sets in PF and 2.3 % in PS). Although antibiotic consumption and medical activity were similar during the two periods, BSI case detection increased from 2.2 to 2.6 per 1,000 hospital-days, especially in intensive care units (ICU; 35.1 to 55.7). Mean TTD for pathogenic microorganisms was significantly shorter in PF than in PS (15.5 h vs 18.0 h,
P
< 0.01). In conclusion, the use of the new FAPlus/FNPlus BC bottles improved the diagnosis of bacteremia in our hospital, especially in ICU patients.
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