Ring signatures allow a user to sign messages as a member of a set of users, which is called the ring. This primitive ensures that nobody can detect which member in the ring signs the message. ...Libert, Peters, and Qian (2018) 24 proposed the first tightly secure ring signature scheme with O(logn) signature size in the random oracle model, where n is the size of a ring. To our knowledge, a tightly secure ring signature scheme has never been reported without depending on the random oracle methodology. In this paper, we propose two generic constructions of tightly secure ring signatures in the standard model. Our first (resp., second) construction is secure in the common reference string model (resp., the plain model). Both of our constructions are secure under the decisional linear assumption over the pairing groups. Our first generic construction has a more efficient instantiation than our second one. While our second generic construction does not have an efficient instantiation, its signature size achieves O(logn) asymptotically, which is the same as one of the Libert et al.'s scheme.
From the work by Laguillaumie and Vergnaud in ICICS’04, it has been widely believed that multi-designated verifiers signature scheme (MDVS) can be constructed from ring signature schemes in general. ...However, in this article, somewhat surprisingly, we prove that it is impossible to construct an MDVS scheme from a ring signature scheme in a black-box sense (in the standard model). The impossibility stems from the difference between the definitions of unforgeability of the two schemes. To the best of our knowledge, existing works demonstrating the constructions do not provide formal reductions from an MDVS scheme to a ring signature scheme, and thus, the impossibility has been overlooked for a long time.
The learning with errors (LWE) problem is one of the fundamental problems in cryptography and it has many applications in post-quantum cryptography. There are two variants of the problem, the ...decisional-LWE problem, and the search-LWE problem. LWE search-to-decision reduction shows that the hardness of the search-LWE problem can be reduced to the hardness of the decisional-LWE problem. The efficiency of the reduction can be regarded as the gap in difficulty between the problems. We initiate a study of quantum search-to-decision reduction for the LWE problem and propose a reduction that satisfies sample-preserving. In sample-preserving reduction, it preserves all parameters even the number of instances. Especially, our quantum reduction invokes the distinguisher only 2 times to solve the search-LWE problem, while classical reductions require a polynomial number of invocations. Furthermore, we give a way to amplify the success probability of the reduction algorithm. Our amplified reduction is incomparable to the classical reduction in terms of sample complexity and query complexity. Our reduction algorithm supports a wide class of error distributions and also provides a search-to-decision reduction for the learning parity with noise problem. In the process of constructing the search-to-decision reduction, we give a quantum Goldreich-Levin theorem over ℤq where q is a prime. In short, this theorem states that, if a hardcore predicate a · s (mod q) can be predicted with probability distinctly greater than 1/q with respect to a uniformly random a ∈ ℤnq, then it is possible to determine s ∈ ℤnq.
In photodynamic therapy (PDT), singlet oxygen (
1
O
2
) is the main species responsible for promoting tumor cell death. The determination of the quantum yield (Φ
Δ
) of a photosensitizer (PS) is ...important for dosimetry. The purpose of this paper is to quantify the
1
O
2
generated by the PS by near-infrared spectroscopy (NIRS). The Φ
Δ
of different PS species were measured by the detection of near-infrared
1
O
2
luminescence. From the measurement results, the Φ
Δ
of talaporfin sodium, protoporphyrin IX (PpIX), and lipidated PpIX (PpIX lipid) were measured as 0.53, 0.77, and 0.87, respectively. In addition, the Φ
Δ
values of PpIX in a hypoxic and oxic solution were evaluated, since tumors are associated with regions of hypoxia. The measured Φ
Δ
indicated a same value at high (DO: 20%) and low (DO: 1%) oxygen concentrations. Using the measured Φ
Δ
, the amount of
1
O
2
generated by the PSs was estimated using
1
O
2
= D*Φ
Δ
, where D* is the total excited PS concentration. The generated
1
O
2
amounts were little different at the high and the low oxygen concentrations, and the generated
1
O
2
amount for each PS was different depending on each Φ
Δ
. The NIRS measurement determined the Φ
Δ
of talaporfin sodium, PpIX, and PpIX lipid. The quantitative evaluation based on the measured Φ
Δ
will support the development of PDT treatment monitoring and design.
Development of surgical support robots began in the 1980s as a navigation and auxiliary device for endoscopic surgery. For remote surgery on the battlefield, a master-slave-type surgical support ...robot was developed, in which a console surgeon operates the robot at will. The da Vinci surgical system, which currently dominates the global robotic surgery market, received United States Food and Drug Administration and regulatory approval in Japan in 2000 and 2009 respectively. The latest, fourth generation, da Vinci Xi has a good field of view via a three-dimensional monitor, highly operable forceps, a motion scale function, and a tremor-filtered articulated function. Gastroenterological tract robotic surgery is safe and minimally invasive when accessing and operating on the esophagus, stomach, colon, and rectum. The learning curve is said to be short, and robotic surgery will likely be standardized soon. Therefore, robotic surgery training should be systematized for young surgeons so that it can be further standardized and later adapted to a wider range of surgeries. This article reviews current trends and potential developments in robotic surgery.
To improve the toughness of epoxy polymers, cross-linked rubber (CLR) particles or core–shell rubber (CSR) particles can be blended into the epoxy matrix. Particle cavitation is thought to be the ...main toughening mechanism of rubber-modified epoxies. Although CLR-modified epoxies have not been studied in depth previously, it is expected that the toughening mechanism differs from that of CSR-modified epoxies because void formation is less likely to occur. We formed the CLR- and CSR-modified epoxy resins using nanosized acrylonitrile butadiene CLR particles, which showed good compatibility with the epoxy matrix and the CSR particles with a rubbery core surrounded by a glassy shell. The toughening mechanism was examined by comparing the fracture behavior, fracture surfaces, and process zones via tensile and fracture toughness testing, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and transmission optical microscopy (TOM). There was a difference in the characteristics of the
R
-curves between the CLR- and CSR-modified epoxies. In addition, the SEM and TEM observations indicated that there was a difference in the fracture mechanism.
Extensive metabolite analysis of Streptomyces rochei 7434AN4 was performed to discover uncharacterized secondary metabolites. A mutant strain of S. rochei, in which two regulatory genes srrC (a ...tetR-type repressor) and srrY (SARP-type activator) were inactivated, accumulated three 4-monosubstituted γ-butyrolactones YT02-A, YT02-B, and KH01-A, which were not detected in the parent strain. Their structures were identified as 4,10-dihydroxy-10-methyldodecan-4-olide, 4,10-dihydroxy-10-methylundecan-4-olide, and 4-hydroxy-11-oxo-10-methyldodecan-4-olide. A structural comparison indicated that the three butanolides and the signaling molecules, termed S. rochei butenolides (SRBs), could share common C12 or C13 fatty acids for their biosynthesis intermediates, however, these three butanolides did not induce antibiotic production even at 50 μM concentration (1000-folds of the minimum antibiotic-inducing concentration of SRBs) in S. rochei.
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We recruited 56 colorectal cancer patients and compared the mutational spectrum of tumor tissue DNA, circulating cell‐free DNA (ccfDNA) and circulating tumor cell (CTC) DNA (ctcDNA) to evaluate the ...potential of liquid biopsy to detect heterogeneity of cancer. Tumor tissue DNA, ccfDNA, and ctcDNA were extracted from each patient and analyzed using next‐generation sequencing (NGS) and digital PCR. To maximize yields of CTC, three antibodies were used in the capture process. From 34 untreated patients, 53 mutations were detected in tumor tissue DNA using NGS. Forty‐seven mutations were detected in ccfDNA, including 20 not detected in tissues. Sixteen mutations were detected in ctcDNA, including five not detected in tissues. In 12 patients (35.3%), mutations not found in tumor tissues were detected by liquid biopsy: nine (26.5%) in ccfDNA only and three (8.8%) in ctcDNA only. Combination analysis of the two liquid biopsy samples increased the sensitivity to detect heterogeneity. From 22 stage IV patients with RAS mutations in their primary tumors, RAS mutations were detected in 14 (63.6%) ccfDNA and in eight (36.4%) ctcDNA using digital PCR. Mutations not detected in primary tumors can be identified in ccfDNA and in ctcDNA, indicating the potential of liquid biopsy in complementing gene analysis. Combination analysis improves sensitivity. Sensitivity to detect cancer‐specific mutations is higher in ccfDNA compared with ctcDNA.
Cancer is a heterogeneous disease. We compared the mutational spectrum of tumor tissue DNA, circulating cell‐free DNA, and circulating tumor cell DNA in colorectal cancer patients using next‐generation sequencing and digital PCR. Results showed the potential of liquid biopsy samples to provide a complementary role in genetic analysis.
Diagnostic markers for recurrence of colorectal cancer have not been established. The aim of the present study was to identify new diagnostic markers for recurrence after curative surgery of stage II ...colon cancer.
In this study, the prognostic values of the preoperative lymphocyte count and the post/preoperative lymphocyte count ratio (PPLR) were evaluated in 142 patients with localized colon cancer treated with surgery at a single medical center. The associations of patient demographics, blood chemistry, and serum biochemical indices with recurrence-free survival (RFS) and cancer-specific survival (CSS) were examined by univariate and multivariate analyses.
Receiver operating characteristic (ROC) curve analysis showed that the optimal cut-off values of the lymphocyte count and PPLR were, respectively, 1555.2/μl and 1.151 for RFS. On univariate analysis, tumor depth of invasion, carbohydrate antigen 19-9 (CA19-9), and preoperative low lymphocyte count (≤1555.2/μl) were all correlated with poorer RFS (
< 0.05). On multivariate analysis, T4, low lymphocyte count, and low PPLR were independent predictors of poor RFS. Furthermore, the patients were categorized into four categories based on preoperative lymphocyte count high/low and PPLR high/low. Patients with a low preoperative lymphocyte count and low PPLR had the poorest RFS and CSS compared to the other patients.
The combination of the preoperative lymphocyte count and the PPLR appears to be a potential marker for predicting recurrence of stage II colon cancer.
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