An extremely low-noise heralded single-photon source: a breakthrough for quantum technologies

Low noise single-photon sources are a critical element for quantum technologies. We present a heralded single-photon source with an extremely low level of residual background photons, by implementing low-jitter detectors and electronics and a fast custom-made pulse generator controlling an optical shutter (a LiNbO3 waveguide optical switch) on the output of the source. This source has a second-order autocorrelation g^{(2)}(0)=0.005(7), and an "Output Noise Factor" (defined as the ratio of the number of noise photons to total photons at the source output channel) of 0.25(1)%. These are the best performance characteristics reported to date

GHz QKD at telecom wavelengths using up-conversion detectors

We have developed a hybrid single photon detection scheme for telecom wavelengths based on nonlinear sum-frequency generation and silicon single-photon avalanche diodes (SPADs). The SPAD devices employed have been designed to have very narrow temporal response, i.e. low jitter, which we can exploit for increasing the allowable bit rate for quantum key distribution. The wavelength conversion is obtained using periodically poled Lithium niobate waveguides (W/Gs). The inherently high efficiency of these W/Gs allows us to use a continuous wave laser to seed the nonlinear conversion so as to have a continuous detection scheme. We also present a 1.27GHz qubit repetition rate, one-way phase encoding, quantum key distribution experiment operating at telecom wavelengths that takes advantage of this detection scheme. The proof of principle experiment shows a system capable of MHz raw count rates with a QBER less than 2% and estimated secure key rates greater than 100 kbit/s over 25 km.Comment: 12 pages, 7 figure

Expression of tumor-associated antigens in breast cancer subtypes

OBJECTIVES: Tumor-associated antigens (TAAs) are frequently overexpressed in several cancer types. The aim of this study was to investigate the expression of TAAs in breast cancer. MATERIAL AND METHODS: A total of 250 selected invasive breast cancers including 50 estrogen receptor (ER)-positive (Luminal B like), 50 triple-negative (TN), 50 ER-positive lobular type, 50 ER- and progesterone receptor (PgR)-positive (Luminal A like) and 50 cerbB2-positive breast cancers, were assessed for New York esophageal squamous cell carcinoma-1 (NY-ESO-1), Wilms tumor antigen (WT-1) and PReferentially expressed Antigen of MElanoma (PRAME) antigen expression by immunohistochemistry (IHC). RESULTS: A significantly higher expression of cancer testis (CT)-antigens NY-ESO-1 and WT-1 antigen was detected in TN breast cancers compared with ER-positive tumors. NY-ESO-1 overexpression (score 2 + and 3+) assessed by monoclonal and polyclonal antibodies was detected in 9 (18%) TN cancers as compared to 2 (4%) ER-positive tumors (p = 0.002). WT1 over-expression (score 2 + and 3+) was confirmed in 27 (54%) TN tumor samples as compared to 6 (12%) ER-positive (p < 0.0001). PRAME over-expression (score 2 + and 3+) was detected in 8 (16%) HER2 positive tumor samples as compared to no TN and ER-positive cancers (p = 0.0021). CONCLUSIONS: NY-ESO-1 and WT1 antigens are overexpressed in TN breast cancers. Because of the limited therapeutic options for this patient subgroup, CT antigen-based vaccines might prove to be useful for patients with this phenotype of breast cancer

Effects of dietary eicosapentaenoic acid on growth, survival, pigmentation and fatty acid composition in Senegal sole (Solea senegalensis) larvae during the Artemia feeding period

We examined the effect of dietary eicosapentaenoic acid (20:5n-3, EPA) on growth, survival, pigmentation and fatty acid composition of Senegal sole larvae using a dose-response design. From 3 to 40 days post hatch (dph), larvae were fed live food that had been enriched using one of four experimental emulsions containing graduated concentrations of EPA and constant docosahexaenoic acid (22:6n-3, DHA) and arachidonic acid (20:4n-6, ARA). Proportions of EPA in the enriched Artemia nauplii were described as “nil” (EPA-N, 0.5% total fatty acids, TFA), “low” (EPA-L, 10.7% TFA), “medium” (EPA-M, 20.3% TFA) or “high” (EPA-H, 29.5% TFA). Significant differences among dietary treatments in larval length were observed at 25, 30 and 40 dph, and in dry weight at 30 and 40 dph, although no significant correlation could be found between dietary EPA content and growth. The stage of eye migration at 17 and 25 dph was significantly affected by dietary levels of EPA. Significantly lower survival was observed in fish fed EPA-H enriched nauplii. A significantly lower percentage of fish fed EPA-N (82.7%) and EPA-L (82.9%) diets were normally pigmented compared to the fish fed EPA-M (98.1%) and EPA-H (99.4%) enriched nauplii. Tissue fatty acid concentrations reflected the corresponding dietary composition. Arachidonic and docosahexaenoic acid levels in all the tissues examined were inversely related to dietary EPA. There was an increase in the proportion of docosapentaenoic acid (22:5n-3, DPA) in the tissues relative to the diet, which is indicative of chain elongation of EPA. This work concluded that Senegal sole larvae have a very low EPA requirement during the live feeding period

Cancer-testis antigen expression in triple-negative breast cancer

Background: Cancer-testis (CT) antigens, frequently expressed in human germline cells but not in somatic tissues, may become aberrantly reexpressed in different cancer types. The aim of this study was to investigate the expression of CT antigens in breast cancer. Patients and methods: A total of 100 selected invasive breast cancers, including 50 estrogen receptor (ER) positive/HER2 negative and 50 triple negative (TN), were examined for NY-ESO-1 and MAGE-A expression by immunohistochemistry. Results: A significantly higher expression of MAGE-A and NY-ESO-1 was detected in TN breast cancers compared with ER-positive tumors (P = 0.04). MAGE-A expression was detected in 13 (26%) TN cancers compared with 5 (10%) ER-positive tumors (P = 0.07). NY-ESO-1 expression was confirmed in nine (18%) TN tumor samples compared with two (4%) ER-positive tumors. Conclusions: MAGE-A and NY-ESO-1 CT antigens are expressed in a substantial proportion of TN breast cancers. Because of the limited therapeutic options for this group of patients, CT antigen-based vaccines might prove to be useful for patients with this phenotype of breast cance

Fatty acid metabolism in marine fish: Low activity of fatty acyl Δ5 desaturation in gilthead sea bream ( Sparus aurata ) cells

Marine fish are known to have an absolute dietary requirement for C20 and C22 highly unsaturated fatty acids. Previous studies using cultured cell lines indicated that underlying this requirement in marine fish was either a deficiency in fatty acyl Δ5 desaturase or C18-20 elongase activity. Recently, Ghioni et al. (Biochim. Biophys. Acta, 1437, 170-181, 1999) presented evidence that in turbot cells there was low activity of C18-20 elongase whereas Δ5 desaturase had high activity. In the present study, the fatty acid desaturase/elongase pathway was investigated in a cell line (SAF-1) from another carnivorous marine fish, sea bream. The metabolic conversions of a range of radiolabelled polyunsaturated fatty acids that comprised the direct substrates for Δ6 desaturase ([1-14C]18:2n-6 and [1-14C]18:3n-3), C18-20 elongase ([U-14C]18:4n-3), Δ5 desaturase ([1-14C]20:3n-6 and [U-14C]20:4n-3) and C20-22 elongase ([1-14C]20:4n-6 and [1-14C]20:5n-3) were utilized. The results showed that fatty acyl Δ6 desaturase in SAF-1 cells was highly active and there was substantial C18-20 elongase and C20-22 elongase activities. A deficiency in the desaturation/elongation pathway was clearly identified at the level of the fatty acyl Δ5 desaturase which was very low, particularly with 20:4n-3 as substrate. In comparison, the apparent activities of Δ6 desaturase, C18-20 elongase and C20-22 elongase were approximately 94-fold, 27-fold and 16-fold greater than that for Δ5 desaturase towards their respective n-3 polyunsaturated fatty acid substrates. The evidence obtained in the SAF-1 cell line is consistent with the dietary requirement for C20 and C22 highly unsaturated fatty acids in the marine fish, the sea bream, being primarily due to a deficiency in fatty acid Δ5 desaturase activity

Analysis of detector performance in a gigahertz clock rate quantum key distribution system

We present a detailed analysis of a gigahertz clock rate environmentally robust phase-encoded quantum key distribution (QKD) system utilizing several different single-photon detectors, including the first implementation of an experimental resonant cavity thin-junction silicon single-photon avalanche diode. The system operates at a wavelength of 850 nm using standard telecommunications optical fibre. A general-purpose theoretical model for the performance of QKD systems is presented with reference to these experimental results before predictions are made about realistic detector developments in this system. We discuss, with reference to the theoretical model, how detector operating parameters can be further optimized to maximize key exchange rates

Highly unsaturated fatty acid synthesis in marine fish: Cloning, functional characterization, and nutritional regulation of fatty acyl delta6 desaturase of Atlantic cod (Gadus morhua L.)

Fish contain high levels of the n-3 highly unsaturated fatty acids (HUFA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids that are crucial to the health of higher vertebrates. Biosynthesis of HUFA requires enzyme-mediated desaturation of fatty acids. Here we report cloning and functional characterisation of a ∆6 fatty acyl desaturase of Atlantic cod (Gadus morhua), and describe its tissue expression and nutritional regulation. PCR primers were designed based on the sequences of conserved motifs in available fish desaturases and used to isolate a cDNA fragment from liver of cod. The full-length cDNA was obtained by Rapid Amplification of cDNA Ends (RACE). The cDNA for the putative fatty acyl desaturase was shown to comprise 1980bp which included a 5’-UTR of 261bp and a 3’-UTR of 375bp. Sequencing revealed that the cDNA included an ORF of 1344 bp that specified a protein of 447 amino acids. The protein sequence included three histidine boxes, two transmembrane regions, and an N-terminal cytochrome b5 domain containing the haem-binding motif HPGG, all of which are characteristic of microsomal fatty acid desaturases. The cDNA displayed Δ6 desaturase activity in a heterologous yeast expression system. Quantitative real time PCR assay of gene expression in cod showed that the ∆6 desaturase gene, was highly expressed in brain, relatively highly expressed in liver, kidney, intestine, red muscle and gill, and expressed at much lower levels in white muscle, spleen and heart. In contrast, the abundance of a cod fatty acyl elongase transcript was high in brain and gill, with intermediate levels in kidney, spleen, intestine and heart, and relatively low expression in liver. The expression of the Δ6 desaturase gene and the PUFA elongase gene may be under a degree of nutritional regulation, with levels being marginally increased in livers and intestine of fish fed a vegetable oil blend by comparison with levels in fish fed fish oil. However, this was not reflected in increased Δ6 desaturase activity in hepatocytes or enterocytes, which showed very little highly unsaturated fatty acid biosynthesis activity irrespective of diet. The study described has demonstrated that Atlantic cod express a fatty acid desaturase gene with functional Δ6 activity in a yeast expression system. This is consistent with an established hypothesis that the poor ability of marine fish to synthesise HUFA is not due to lack of a Δ6 desaturase, but rather to deficiencies in other parts of the biosynthetic pathway. However, further studies are required to determine why the Δ6 desaturase appears to be barely functional in cod under the conditions tested

Cultured fish cells metabolize octadecapentaenoic acid (all-cis delta3,6,9,12,15–18∶5) to octadecatetraenoic acid (all-cis delta6,9,12,15–18∶4) via its 2-trans intermediate (trans delta2, all-cis delta6,9,12,15–18∶5)

Octadecapentaenoic acid (all-cis Δ3,6,9,12,15-18:5; 18:5n-3) is an unusual fatty acid found in marine dinophytes, haptophytes and prasinophytes. It is not present at higher trophic levels in the marine food web but its metabolism by animals ingesting algae is unknown. Here we studied the metabolism of 18:5n-3 in cell lines derived from turbot (Scophthalmus maximus), gilthead sea bream (Sparus aurata) and Atlantic salmon (Salmo salar). Cells were incubated in the presence of approximately 1 μM [U-14C] 18:5n-3 methyl ester or [U-14C] 18:4n-3 (octadecatetraenoic acid; all-cis Δ6,9,12,15-18:4) methyl ester, both derived from the alga Isochrysis galbana grown in H14CO3, and also with 25 μM unlabelled 18:5n-3 or 18:4n-3. Cells were also incubated with 25 μM trans Δ2, all-cis Δ6,9,12,15-18:5 (2-trans 18:5n-3) produced by alkaline isomerization of 18:5n-3 chemically synthesized from docosahexaenoic acid (all-cis Δ4,7,10,13,16,19-22:6; 22:6n-3). Radio- and mass analyses of total fatty acids extracted from cells incubated with 18:5n-3 were consistent with this fatty acid being rapidly metabolized to 18:4n-3 which was then elongated and further desaturated to eicosatetraenoic acid (all-cis Δ8,11,14,17,19-20:4; 20:4n-3) and eicosapentaenoic acid (all-cis Δ5,8,11,14,17-20:5; 20:5n-3). Similar mass increases of 18:4n-3 and its elongation and further desaturation products occurred in cells incubated with 18:5n-3 or 2-trans 18:5n-3. We conclude that 18:5n-3 is readily converted biochemically to 18:4n-3 via a 2-trans 18:5n-3 intermediate generated by a Δ3,Δ2-enoyl-CoA-isomerase acting on 18:5n-3. Thus, 2-trans 18:5n-3 is implicated as a common intermediate in the β-oxidation of both 18:5n-3 and 18:4n-3

Investigation of highly unsaturated fatty acid metabolism in the Asian sea bass, Lates calcarifer

Lates calcarifer, commonly known as the Asian sea bass or barramundi, is an interesting species that has great aquaculture potential in Asia including Malaysia and also Australia. We have investigated essential fatty acid metabolism in this species, focusing on the endogenous highly unsaturated fatty acid (HUFA) synthesis pathway using both biochemical and molecular biological approaches. Fatty acyl desaturase (Fad) and elongase (Elovl) cDNAs were cloned and functional characterization identified them as ∆6 Fad and Elovl5 elongase enzymes, respectively. The ∆6 Fad was equally active towards 18:3n-3 and 18:2n-6, and Elovl5 exhibited elongation activity for C18-20 and C20-22 elongation and a trace of C22-24 activity. The tissue profile of gene expression for ∆6 fad and elovl5 genes, showed brain to have the highest expression of both genes compared to all other tissues. The results of tissue fatty acid analysis showed that the brain contained more docosahexaenoic acid (DHA, 22:6n-3) than flesh, liver and intestine. The HUFA synthesis activity in isolated hepatocytes and enterocytes using [1-14C]18:3n-3 as substrate was very low with the only desaturated product detected being 18:4n-3. These findings indicate that L. calcarifer display an essential fatty acid pattern similar to other marine fish in that they appear unable to synthesize HUFA from C18 substrates. High expression of ∆6 fad and elovl5 genes in brain may indicate a role for these enzymes in maintaining high DHA levels in neural tissues through conversion of 20:5n-3