Multi-Prover Commitments Against Non-Signaling Attacks

We reconsider the concept of multi-prover commitments, as introduced in the late eighties in the seminal work by Ben-Or et al. As was recently shown by Cr\'{e}peau et al., the security of known two-prover commitment schemes not only relies on the explicit assumption that the provers cannot communicate, but also depends on their information processing capabilities. For instance, there exist schemes that are secure against classical provers but insecure if the provers have quantum information processing capabilities, and there are schemes that resist such quantum attacks but become insecure when considering general so-called non-signaling provers, which are restricted solely by the requirement that no communication takes place. This poses the natural question whether there exists a two-prover commitment scheme that is secure under the sole assumption that no communication takes place; no such scheme is known. In this work, we give strong evidence for a negative answer: we show that any single-round two-prover commitment scheme can be broken by a non-signaling attack. Our negative result is as bad as it can get: for any candidate scheme that is (almost) perfectly hiding, there exists a strategy that allows the dishonest provers to open a commitment to an arbitrary bit (almost) as successfully as the honest provers can open an honestly prepared commitment, i.e., with probability (almost) 1 in case of a perfectly sound scheme. In the case of multi-round schemes, our impossibility result is restricted to perfectly hiding schemes. On the positive side, we show that the impossibility result can be circumvented by considering three provers instead: there exists a three-prover commitment scheme that is secure against arbitrary non-signaling attacks

Breast reconstruction affects coping mechanisms in breast cancer survivors.

Coping strategies used by women with breast cancer are vital for adjustment to their disease. Whilst it is clear that factors such as age at diagnosis, social support and ethnicity can influence coping mechanisms, there is currently no information about whether breast reconstruction changes mechanisms of coping for such patients. The aims of this study, therefore, were to determine how women who have had immediate breast reconstruction and mastectomy cope, compared to those who have mastectomy alone, and whether there are differences in coping mechanisms due to breast reconstruction surgery. This was a retrospective cohort study, using a standardised questionnaire called the Brief Cope Scale. Inclusion criteria was the following: all women who had immediate breast reconstruction and mastectomy in Shropshire from 2003 to 2014 for ductal carcinoma in situ or node-negative invasive breast cancer. Each patient was matched for year of diagnosis, adjuvant therapy and age to one woman who had mastectomy alone. Two hundred thirty-four questionnaires were sent with a 58% response rate. Significantly more patients from the reconstruction cohort coped by active coping (T value 1.66, P value 0.04) compared to those in the mastectomy alone cohort. In contrast, significantly more patients in the mastectomy alone cohort coped by active venting compared to the reconstruction cohort (T value 1.71, P value 0.04). This study indicates for the first time that breast reconstruction may alter coping mechanisms in breast cancer survivors. Awareness of these coping mechanisms will enable clinicians to provide appropriate, individualised support

Metabolism of wheat dextrin, partially hydrolysed guar gum and insulin combined with either Bifidobacterium lactis or Lactobacillus acidophilus in an in vitro gut model fermentation

Combining the fibres wheat dextrin (WD), partially hydrolysed guar gum (PHGG) and inulin with probiotics Lactobacillus acidophilus NCFM (NCFM) or Bifidobacterium lactis HN019 (HN019) may enhance bacterial metabolites leading to a healthier gut community. The aim of this study was to determine whether WD, PHGG and inulin or NCFM and HN019 alone generate a more favourable gut bacterial community than when combined. A secondary aim was to assess organic acid production following prebiotics, probiotics and synbiotic fermentation. An in vitro gut model batch culture fermentation was run for 72 h. Samples were collected for bacterial enumeration (fluorescent in situ hybridisation combined with flow cytometry) and organic acid production (gas chromatography). Inulin and HN019 combination significantly increased bifidobacteria compared to inulin alone. Additionally, a significant increase in lactic acid bacteria, Bacteroides and Clostridium coccoides-Eubacterium rectale was found in the inulin containing probiotic vessels. The WD and PHGG vessels combined with the probiotic did not show any alteration in bacterial metabolism compared to the dietary fibres alone. In conclusion, synbiotic inulin combined with either HN019 or NCFM may help to enhance bacterial metabolites and cross-feeding to lead to a prolonged elevation in Bifidobacterium spp., and lactic acid bacteria

Pectic oligosaccharide structure-function relationships: prebiotics, inhibitors of Escherichia coli O157:H7 adhesion and reduction of Shiga toxin cytotoxicity in HT29 cells

Shiga toxin (Stx)-producing, food-contaminating Escherichia coli (STEC) is a major health concern. Plant-derived pectin and pectic-oligosaccharides (POS) have been considered as prebiotics and for the protection of humans from Stx. Of five structurally different citrus pectic samples, POS1, POS2 and modified citrus pectin 1 (MCP1) were bifidogenic with similar fermentabilities in human faecal cultures and arabinose-rich POS2 had the greatest prebiotic potential. Pectic oligosaccharides also enhanced lactobacilli growth during mixed batch faecal fermentation. We demonstrated that all pectic substrates were anti-adhesive for E. coli O157:H7 binding to human HT29 cells. Lower molecular weight and deesterification enhanced the anti-adhesive activity. We showed that all pectic samples reduced Stx2 cytotoxicity in HT29 cells, as measured by the reduction of human rRNA depurination detected by our novel TaqMan-based RT-qPCR assay, with POS1 performing the best. POS1 competes with Stx2 binding to the Gb3 receptor based on ELISA results, underlining the POS anti-STEC properties

Understanding the influence of processing conditions on the extraction of rhamnogalacturonan-I “hairy” pectin from sugar beet pulp

Sugar beet pectin is rich in rhamnogalacturonan-I (RG-I) region, which is a potential source of prebiotics. RG-I pectin cannot be extracted the same way as commercial homogalacturan-rich pectin using hot acid. Therefore, this study has explored several alternative methods, including microwave-assisted extraction (MAE) and conventional- solvent extraction (CSE) at atmospheric pressure using different solvents, and microwave-assisted hydrothermal extraction (MAHE) under pressure using water. No conclusive differences in microwave and conventional heating were found with heating rate controlled. The optimum treatment times of both MAE and CSE at 90 °C atmospheric pressure and regardless of the solvents used were 120 min; however, MAHE at 130 °C under pressure can dramatically reduce the time to 10 min. Alcohol-insoluble solids (AIS) extracted using pH13 solvent by MAE had both the highest RG-I yield at 25.3% and purity at 260.2 mg/g AIS, followed by AIS extracts using water by MAHE with 7.5% and 166.7 mg/g AIS respectively

A note on "symmetric" vielbeins in bimetric, massive, perturbative and non perturbative gravities

We consider a manifold endowed with two different vielbeins $E^{A}{}_{\mu}$ and $L^{A}{}_{\mu}$ corresponding to two different metrics $g_{\mu\nu}$ and $f_{\mu\nu}$. Such a situation arises generically in bimetric or massive gravity (including the recently discussed version of de Rham, Gabadadze and Tolley), as well as in perturbative quantum gravity where one vielbein parametrizes the background space-time and the other the dynamical degrees of freedom. We determine the conditions under which the relation $g^{\mu\nu} E^{A}{}_{\mu} L^{B}{}_{\nu} = g^{\mu\nu} E^{B}{}_{\mu} L^{A}{}_{\nu}$ can be imposed (or the "Deser-van Nieuwenhuizen" gauge chosen). We clarify and correct various statements which have been made about this issue.Comment: 20 pages. Section 7, prop. 6 and 7. added. Some results made more precis

Quantum-classical transition in Scale Relativity

The theory of scale relativity provides a new insight into the origin of fundamental laws in physics. Its application to microphysics allows us to recover quantum mechanics as mechanics on a non-differentiable (fractal) spacetime. The Schrodinger and Klein-Gordon equations are demonstrated as geodesic equations in this framework. A development of the intrinsic properties of this theory, using the mathematical tool of Hamilton's bi-quaternions, leads us to a derivation of the Dirac equation within the scale-relativity paradigm. The complex form of the wavefunction in the Schrodinger and Klein-Gordon equations follows from the non-differentiability of the geometry, since it involves a breaking of the invariance under the reflection symmetry on the (proper) time differential element (ds - ds). This mechanism is generalized for obtaining the bi-quaternionic nature of the Dirac spinor by adding a further symmetry breaking due to non-differentiability, namely the differential coordinate reflection symmetry (dx^mu - dx^mu) and by requiring invariance under parity and time inversion. The Pauli equation is recovered as a non-relativistic-motion approximation of the Dirac equation.Comment: 28 pages, no figur