1,174 research outputs found
Revisiting Scalarization in Multi-Task Learning: A Theoretical Perspective
Linear scalarization, i.e., combining all loss functions by a weighted sum,
has been the default choice in the literature of multi-task learning (MTL)
since its inception. In recent years, there is a surge of interest in
developing Specialized Multi-Task Optimizers (SMTOs) that treat MTL as a
multi-objective optimization problem. However, it remains open whether there is
a fundamental advantage of SMTOs over scalarization. In fact, heated debates
exist in the community comparing these two types of algorithms, mostly from an
empirical perspective. To approach the above question, in this paper, we
revisit scalarization from a theoretical perspective. We focus on linear MTL
models and study whether scalarization is capable of fully exploring the Pareto
front. Our findings reveal that, in contrast to recent works that claimed
empirical advantages of scalarization, scalarization is inherently incapable of
full exploration, especially for those Pareto optimal solutions that strike the
balanced trade-offs between multiple tasks. More concretely, when the model is
under-parametrized, we reveal a multi-surface structure of the feasible region
and identify necessary and sufficient conditions for full exploration. This
leads to the conclusion that scalarization is in general incapable of tracing
out the Pareto front. Our theoretical results partially answer the open
questions in Xin et al. (2021), and provide a more intuitive explanation on why
scalarization fails beyond non-convexity. We additionally perform experiments
on a real-world dataset using both scalarization and state-of-the-art SMTOs.
The experimental results not only corroborate our theoretical findings, but
also unveil the potential of SMTOs in finding balanced solutions, which cannot
be achieved by scalarization.Comment: Accepted at NeurIPS 202
Data Processing Pipeline for Pointing Observations of Lunar-based Ultraviolet Telescope
We describe the data processing pipeline developed to reduce the pointing
observation data of Lunar-based Ultraviolet Telescope (LUT), which belongs to
the Chang'e-3 mission of the Chinese Lunar Exploration Program. The pointing
observation program of LUT is dedicated to monitor variable objects in a
near-ultraviolet (245-345 nm) band. LUT works in lunar daytime for sufficient
power supply, so some special data processing strategies have been developed
for the pipeline. The procedures of the pipeline include stray light removing,
astrometry, flat fielding employing superflat technique, source extraction and
cosmic rays rejection, aperture and PSF photometry, aperture correction, and
catalogues archiving, etc. It has been intensively tested and works smoothly
with observation data. The photometric accuracy is typically ~0.02 mag for LUT
10 mag stars (30 s exposure), with errors come from background noises,
residuals of stray light removing, and flat fielding related errors. The
accuracy degrades to be ~0.2 mag for stars of 13.5 mag which is the 5{\sigma}
detection limit of LUT.Comment: 10 pages, 7 figures, 4 tables. Minor changes and some expounding
words added. Version accepted for publication in Astrophysics and Space
Science (Ap&SS
Klinička primjena RT-PCR u otkrivanju DNK tuberkuloze u kombinaciji s TB-IGRA u dijagnostici plućne tuberkuloze s negativnim nalazom sputuma
The aim was to investigate detection of pulmonary alveolar lavage fluid tuberculosis
DNA by real-time fluorescent polymerase chain reaction (RT-PCR) combined with clinical application
of the sputum smear-negative pulmonary tuberculosis diagnosis with TB interferon-γ release
assay (TB-IGRA). From October 2014 to October 2015, 632 outpatients and inpatients treated in our
hospital were randomly selected, of which 459 patients as the research group managed with RT-PCR
detection combined with TB-IGRA and 173 patients as the control group undergoing electronic
bronchoscopy alveolar lavage fluid detection, with detection results statistically evaluated. The positive
rate in the research group was 96.51%, i.e. significantly higher than that in the control group (66.47%),
yielding a statistically significant difference (χ2=109.68, p=0.00). The true positive rate was 97.7% in
the research group and 67.92% in the control group; the true positive rate was significantly higher in
the research group patients as compared with the control group, yielding a statistically significant difference
(χ2=112.04, p=0.00). The sensitivity and specificity, as well as Youden index were significantly
higher in the research group as compared with the control group. In conclusion, TB DNA detection
by RT-PCR combined with TB-IGRA is a very good method of diagnosing tuberculosis, and it can
be implemented in clinical diagnosis of pulmonary tuberculosis.Cilj istraživanja bio je ispitati otkrivanje DNK tuberkuloze u plućnom alveolarnom ispirku pomoću lančane reakcije
polimeraze u stvarnom vremenu s fluorescentnim bojama (RT-PCR) u kombinaciji s kliničkom primjenom dijagnostike
plućne tuberkuloze s negativnim nalazom sputuma pomoću testa otpuštanja TB interferona-γ (TB-IGRA). Od listopada
2014. do listopada 2015. godine nasumce su odabrane 632 osobe bolnički i izvanbolnički liječene u našoj bolnici, od kojih
je 459 uključeno u ispitnu skupinu podvrgnutu otkrivanju pomoću RT-PCR u kombinaciji s testom TB-IGRA, a 173 u
kontrolnu skupinu podvrgnutu elektroničkom otkrivanju u bronhoskopskom alveolarnom ispirku; rezultati su statistički
obrađeni. Stopa pozitivnih nalaza bila je 96,51% u ispitnoj skupini, odnosno značajno viša od one u kontrolnoj skupini
(66,47%), uz statistički značajnu razliku (χ2=109,68; p=0,00). Stopa stvarno pozitivnih nalaza bila je 97,7% u ispitnoj skupini
i 67,92% u kontrolnoj skupini, dakle značajno viša kod bolesnika ispitne skupine u usporedbi s kontrolnom skupinom, uz
statistički značajnu razliku (χ2=112,04; p=0,00). Osjetljivost i specifičnost, kao i Youdenov indeks bili su značajno viši u
ispitnoj skupini u usporedbi s kontrolnom skupinom. U zaključku, otkrivanje TB DNK pomoću RT-PCR u kombinaciji s
TB-IGRA vrlo je dobra metoda za dijagnosticiranje tuberkuloze, koja se može primjenjivati u kliničkoj dijagnostici plućne
tuberkuloze
pts promoter influences antibiotic resistance via proton motive force and ROS in Escherichia coli
IntroductionGlucose level is related to antibiotic resistance. However, underlying mechanisms are largely unknown.MethodsSince glucose transport is performed by phosphotransferase system (PTS) in bacteria, pts promoter-deleted K12 (Δpts-P) was used as a model to investigate effect of glucose metabolism on antibiotic resistance. Gas chromatography-mass spectrometry based metabolomics was employed to identify a differential metabolome in Δpts-P compared with K12, and with glucose as controls.ResultsΔpts-P exhibits the resistance to β-lactams and aminoglycosides but not to quinolones, tetracyclines, and macrolide antibiotics. Inactivated pyruvate cycle was determined as the most characteristic feature in Δpts-P, which may influence proton motive force (PMF), reactive oxygen species (ROS), and nitric oxide (NO) that are related to antibiotic resistance. Thus, they were regarded as three ways for the following study. Glucose promoted PMF and β-lactams-, aminoglycosides-, quinolones-mediated killing in K12, which was inhibited by carbonyl cyanide 3-chlorophenylhydrazone. Exogenous glucose did not elevated ROS in K12 and Δpts-P, but the loss of pts promoter reduced ROS by approximately 1/5, which was related to antibiotic resistance. However, NO was neither changed nor related to antibiotic resistance.DiscussionThese results reveal that pts promoter regulation confers antibiotic resistance via PMF and ROS in Escherichia coli
Razvoj kvantitativnog PCR testa temeljenog na SYBR Green I za identifikaciju cirkovirusa svinja 1, 2 i 3
Porcine Circovirus (PCV) includes Porcine Circovirus 1(PCV1), Porcine Circovirus 2 (PCV2) and Porcine Circovirus 3 (PCV3). In recent years, co-infection exists between PCV1, PCV2 and PCV3 serotypes. Therefore, it is particularly necessary to establish a fast, specific and sensitive SYBR Green I real-time quantitative PCR detection method for PCV1, PCV2 and PCV3. In this experiment, specific primers were selected and the reaction conditions were optimized. A real-time quantitative PCR identification method was established. The results showed the detection limits of this assay were 40.3 copies/μl for PCV1, 25.2 copies/μl for PCV2 and22.4 copies/ μl for PCV3. There was no cross-reactivity with swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine pseudorabies virus (PRV) and porcine parvovirus (PPV). The intra-assay and inter-assay coefficients of variation were less than 1%. The test results of 100 PCV suspected positive samples revealed that the PCV1, PCV2 and PCV3 singular infection rate was 10% (10/100), 64% (64/100) and 52% (52/100), respectively. The PCV1 and PCV2 co-infection rate was 8% (8/100), the PCV1 and PCV3 co-infection rate was 7% (7/100), the PCV2 and PCV3 co-infection rate was 26% (26/100), and the PCV1, PCV2 and PCV3 co-infection rate was 7% (7/100). This method has good specificity, sensitivity and stability. It provides a promising tool for rapid differential detection of PCV1, PCV2 and PCV3.Među cirkovirusima svinja razlikujemo cirkovirus svinja tipa 1 (PCV1), cirkovirus svinja tipa 2 (PCV2) i cirkovirus svinja tipa 3 (PCV3). Posljednjih se godina pojavljuje koinfekcija ovim trima serotipovima, stoga je potrebno uspostaviti brzu, specifičnu i osjetljivu metodu kako bi se kvantitativnim PCR testom temeljenom na SYBR Green I mogli identificirati PCV1, PCV2 i PCV3. U ovom su istraživanju upotrijebljene specifične početnice te su optimizirani uvjeti rekacije za uspostavljanje kvantitativnog PCR-a u stvarnom vremenu. Rezultati su pokazali da su granice detekcije ovog testa 40,3 kopije/μL za PCV1, 25,2 kopije/μL za PCV2 i 22,4 kopije/μL za PCV3. Nije bilo križne reaktivnosti s virusom svinjske kuge (CSFV), virusom reproduktivnog i respiratornog sindroma svinja (PRRSV), virusom pseudobjesnoće svinja (PRV) i parvovirusom svinja (PPV). Koeficijenti varijacije unutar testa i među testovima bili su manji od 1 %. Rezultati analize 100 uzoraka sa sumnjom na PCV pokazali su da je stopa infekcije serotipom PCV1 bila 10% (10/100), PCV2 64% (64/100), a PCV3 52% (52/100). Stopa koinfekcije serotipovima PCV1 i PCV2 bila je 8% (8/100), PCV1 i PCV3 7% (7/100), a PCV2 i PCV3 26% (26/100). Koinfekcija svim trima serotipovima, PCV1, PCV2 i PCV3, bila je 7% (7/100). Metoda primjenjena u ovom istraživanju ima dobru specifičnost, osjetljivost i postojanost te je obećavajući alat za brzo otkrivanje serotipova PCV1, PCV2 i PCV3
Photon upconversion through triplet exciton-mediated energy relay.
Exploration of upconversion luminescence from lanthanide emitters through energy migration has profound implications for fundamental research and technology development. However, energy migration-mediated upconversion requires stringent experimental conditions, such as high power excitation and special migratory ions in the host lattice, imposing selection constraints on lanthanide emitters. Here we demonstrate photon upconversion of diverse lanthanide emitters by harnessing triplet exciton-mediated energy relay. Compared with gadolinium-based systems, this energy relay is less dependent on excitation power and enhances the emission intensity of Tb3+ by 158-fold. Mechanistic investigations reveal that emission enhancement is attributable to strong coupling between lanthanides and surface molecules, which enables fast triplet generation (<100 ps) and subsequent near-unity triplet transfer efficiency from surface ligands to lanthanides. Moreover, the energy relay approach supports long-distance energy transfer and allows upconversion modulation in microstructures. These findings enhance fundamental understanding of energy transfer at molecule-nanoparticle interfaces and open exciting avenues for developing hybrid, high-performance optical materials
Navigating the depths: a stratification-aware coarse-to-fine received signal strength-based localization for internet of underwater things
Underwater wireless sensor networks (UWSNs) are the primary enabling technology for the Internet of underwater things (IoUT), with which all underwater objects can interact and communicate. In UWSNs, localization is vital for military or civilized applications since data collected without location are meaningless. However, accurate localization using acoustic signals in UWSNs is challenging, especially for received signal strength (RSS)-based techniques. The adverse effect of hybrid loss (path and absorption loss) and stratified propagation may severely impact localization accuracy. Even though some schemes have been proposed in the literature, the accuracy is unsatisfactory. To this end, this study proposes a coarse-to-fine localization method (CFLM). The problem is reformed into an alternating nonnegative constrained least squares (ANCLS) framework, where a constrained ellipse adjustment (CEA) using block principal pivoting is proposed to obtain the coarse estimation. A refined step using a Taylor series expansion is then further presented, in which a corrected solution is acquired by iteration. Additionally, this study derives the Cramér-Rao lower bound (CRLB) to evaluate the proposed method. Simulation results show that the proposed CFLM improves the localization accuracy by up to 66 percent compared with weighted least squares (WLS), privacy-preserving localization (PPSL), two-step linearization localization approach (TLLA), particle swarm optimization-based (PSO) localization, and differential evolution-based (DE) localization under different scenarios
Experimentally obtaining the Likeness of Two Unknown Quantum States on an NMR Quantum Information Processor
Recently quantum states discrimination has been frequently studied. In this
paper we study them from the other way round, the likeness of two quantum
states. The fidelity is used to describe the likeness of two quantum states.
Then we presented a scheme to obtain the fidelity of two unknown qubits
directly from the integral area of the spectra of the assistant qubit(spin) on
an NMR Quantum Information Processor. Finally we demonstrated the scheme on a
three-qubit quantum information processor. The experimental data are consistent
with the theoretical expectation with an average error of 0.05, which confirms
the scheme.Comment: 3 pages, 4 figure
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