588 research outputs found
Avoiding the Detector Blinding Attack on Quantum Cryptography
We show the detector blinding attack by Lydersen et al [1] will be
ineffective on most single photon avalanche photodiodes (APDs) and certainly
ineffective on any detectors that are operated correctly. The attack is only
successful if a redundant resistor is included in series with the APD, or if
the detector discrimination levels are set inappropriately
Efficient generation of tunable photon pairs at 0.8 and 1.6 micrometer
We demonstrate efficient generation of collinearly propagating, highly
nondegenerate photon pairs in a periodically-poled lithium niobate cw
parametric downconverter with an inferred pair generation rate of 1.4*10^7/s/mW
of pump power. Detection of an 800-nm signal photon triggers a
thermoelectrically-cooled 20%-efficient InGaAs avalanche photodiode for the
detection of the 1600-nm conjugate idler photon. Using single-mode fibers as
spatial mode filters, we obtain a signal-conditioned idler-detection
probability of about 3.1%.Comment: 8 pages, 3 figure
Exploring two distinct gentamicin prescribing protocols in UK hospitals: a mixed-methods realist evaluation.
This is the final version. Available from BMJ Publishing via the DOI in this record. Data availability statement: Data are available upon reasonable request.
The raw data cannot be made freely available to share, given the nature of the
consents given by participants. However, the corresponding author (ND ORCID ID:
0000-0002-8797-3467) can be contacted to discuss possible secondary analyses
of deidentified participant data.OBJECTIVES: Gentamicin is the aminoglycoside antibiotic of choice in the UK. It has a narrow therapeutic index: underdosing results in inefficacy while overdosing is characterised by nephrotoxicity and ototoxicity. To improve patient safety, hospitals have protocols for the prescription of gentamicin, which vary in complexity and approach. This study aimed to explore two distinct protocols for prescribing gentamicin in hospital settings, in order to understand the mechanisms they trigger and the outcomes they achieve. SETTING: A mixed-methods realist evaluation explored gentamicin prescribing protocols in two hospital surgical admissions units in South West England between January and August 2018. Site 1 had a traditional, complex protocol, while site 2 took a simplified protocol. PARTICIPANTS: Testing the initial programme theory (IPT) involved semi-structured audio-recorded interviews of a volunteer sample of healthcare professionals (HCPs) involved in the prescribing and administering process, alongside a clinical audit reviewing accuracy of gentamicin prescribing. OUTCOME MEASURES: Three sequential phases were used to identify factors in a successful protocol: IPT generation; testing; refinement of the IPT. The IPT was generated by literature search and analysis of existing protocols of sites 1 and 2. Refinement of the IPT synthesised the results of the quantitative and qualitative research to identify the key characteristics of a successful protocol. RESULTS: One hundred gentamicin prescriptions were reviewed, with a mean accuracy of gentamicin prescribing at site 1 of 65.67% and at site 2 of 78.79% (p<0.01). Thirty HCPs were interviewed. Key contexts were identified including prescriptiveness, experience and availability of patient information. These triggered hidden mechanisms including uncertainty, fear, confidence and frustration leading to both intended outcomes but also unintended outcomes such as deviation from protocol and unnecessary gentamicin levels. CONCLUSIONS: A simplified prescribing protocol for gentamicin is better accepted by prescribers, leading to better adherence to protocol and more accurate prescribing
Electron-Phonon Coupling in Charged Buckminsterfullerene
A simple, yet accurate solution of the electron-phonon coupling problem in
C_{60} is presented. The basic idea behind it is to be found in the
parametrization of the ground state electronic density of the system calculated
making use of ab-initio methods, in term of sp hybridized orbitals.
This parametrization allows for an economic determination of the deformation
potential associated with the fullerene's normal modes. The resulting
electron-phonon coupling constants are used to calculate Jahn-Teller effects in
C_{60}^-, and multiple satellite peaks in the corresponding photoemission
reaction. Theory provides an accurate account of the experimental findings.Comment: 11 pages, 3 figures. Accepted for publication in Chem. Phys. Let
Pressure dependence of the thermoelectric power of single-walled carbon nanotubes
We have measured the thermoelectric power (S) of high purity single-walled
carbon nanotube mats as a function of temperature at various hydrostatic
pressures up to 2.0 GPa. The thermoelectric power is positive, and it increases
in a monotonic way with increasing temperature for all pressures. The low
temperature (T < 40 K) linear thermoelectric power is pressure independent and
is characteristic for metallic nanotubes. At higher temperatures it is enhanced
and though S(T) is linear again above about 100 K it has a nonzero intercept.
This enhancement is strongly pressure dependent and is related to the change of
the phonon population with hydrostatic pressure.Comment: 4 pages, 3 figure
Thermodynamic description of Be(II) solubility and hydrolysis in acidic to hyperalkaline NaCl and KCl solutions
The solubility of Be(II) is investigated in carbonate-free dilute to concentrated HCl–NaCl–NaOH, KCl–KOH, NaOH and KOH solutions. Undersaturation experiments were performed under Ar atmosphere at T= (22 ± 2) °C. XRD, XPS, SEM and quantitative chemical analysis confirm that α-Be(OH)(cr) is the solid phase controlling the solubility in all evaluated systems. No transformation of α-Be(OH)(cr) to β-Be(OH)(cr) or ternary solid phases Na/K–Be(II)–OH(s) is observed in the investigated systems within the timeframe of this study (t ≤ 600 days). An amphoteric solubility behaviour of Be(II) is observed with a solubility minimum at pH ≈ 9.5 (with [Be(II)] ≈ 10M), regardless of the ionic strength. The combination of solubility data determined in acidic pH conditions and the hydrolysis scheme reported in the literature for cationic hydrolysis species of Be(II) is used for the determination of the solubility constant of α-Be(OH)(cr), log *K° = (6.9 ± 0.4). Slope analysis of the solubility data in alkaline to hyperalkaline conditions and Be NMR support the predominance of the monomeric hydrolysis species Be(OH)(aq), Be(OH)– and Be(OH) within the strongly alkaline pH-conditions relevant in cementitious systems. The comprehensive solubility dataset collected within this study in combination with extensive solid and aqueous phase characterization allow the development of a complete chemical, thermodynamic and (SIT) activity model for the system Be–Na–K–H–Cl–OH–HO(l). This model provides an accurate and robust tool for the evaluation of Be(II) solubility and speciation in a diversity of geochemical conditions, including source term calculations of beryllium in the context of the nuclear waste disposal Safety Case
Targeted capture of Dreb subfamily genes as candidates genes for drought tolerance polymorphism in natural population of Coffea canephora.
Coffea canephora, (Robusta), provides 33% of worldwide coffee production, 80% and 22% of Ugandan and Brazilian coffee production, respectively. Abiotic stress such as temperature variations or drought periods, aggravated by climate changes, are factors that affect this production. This sensitivity threatens both the steady supply of quality coffees and the livelihood of millions of people producing coffee. The natural genetic diversity of C. canephora offer a potential for detecting new genetic variants related to drought adaptation. In particular, modifications occurring in genes related to abiotic stress tolerance make these genes candidate for breeding programs in order to enhance the resilience to climate change
Experimental implementation of time-coding quantum key distribution
We have implemented an experimental set-up in order to demonstrate the
feasibility of time-coding protocols for quantum key distribution. Alice
produces coherent 20 ns faint pulses of light at 853 nm. They are sent to Bob
with delay 0 ns (encoding bit 0) or 10 ns (encoding bit 1). Bob directs at
random the received pulses to two different arms. In the first one, a 300 ps
resolution Si photon-counter allows Bob to precisely measure the detection
times of each photon in order to establish the key. Comparing them with the
emission times of the pulses sent by Alice allows to evaluate the quantum bit
error rate (QBER). The minimum obtained QBER is 1.62 %. The possible loss of
coherence in the set-up can be exploited by Eve to eavesdrop the line.
Therefore, the second arm of Bob set-up is a Mach-Zender interferometer with a
10 ns propagation delay between the two path. Contrast measurement of the
output beams allows to measure the autocorrelation function of the received
pulses that characterizes their average coherence. In the case of an ideal
set-up, the value expected with the pulses sent by Alice is 0.576. The
experimental value of the pulses autocorrelation function is found to be 0.541.
Knowing the resulting loss of coherence and the measured QBER, one can evaluate
the mutual information between Alice and Eve and the mutual information between
Alice and Bob, in the case of intercept-resend attacks and in the case of
attacks with intrication. With our values, Bob has an advantage on Eve of 0.43
bit per pulse. The maximum possible QBER corresponding to equal informations
for Bob and Eve is 5.8 %. With the usual attenuation of fibres at 850 nm, it
shows that secure key distribution is possible up to a distance of 2.75 km,
which is sufficient for local links.Comment: 27 pages, 6 figure
- …