Ultra-broadband photon pair preparation by spontaneous four wave mixing in dispersion-engineered optical fiber

We present a study of the spectral properties of photon pairs generated through the process of spontaneous four wave mixing (SFWM) in single mode fiber. Our analysis assumes narrowband pumps, which are allowed to be frequency-degenerate or non-degenerate. Based on this analysis, we derive conditions on the pump frequencies and on the fiber dispersion parameters which guarantee the generation of ultra-broadband photon pairs. Such photon pairs are characterized by: i) a very large degree of entanglement, and ii) a very high degree of temporal synchronization between the signal and idler photons. Through a numerical exercise, we find that the use of photonic crystal fiber (PCF) facilitates the fulfilment of the conditions for ultra-broadband photon pair generation; in particular, the spectral region in which emission occurs can be adjusted to particular needs through an appropriate choice of the PCF parameters. In addition, we present a novel quantum interference effect, resulting from indistinguishable pathways to the same outcome, which can occur when pumping a SFWM source with multiple spectral lines.Comment: 15 pages, 10 figures. To be published in Phys. Rev.

Yield of forage, grain and biomass in eight hybrids of maize with different sowing dates and environmental conditions

The aim was to evaluate yield of forage, grain and biomass and fibre content of eight hybrids of maize (Rio-Grande, Arrayan, Genex 778, Narro 2010, Advance 2203, DAS 2358, P4082W and HT9150W) during two sowing seasons (spring/summer) for two consecutive years at La Laguna in Torreon, Mexico. Once the grain progression of the kernel milk line was ⅓, green forage yield (GFY), dry matter (DM), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined. When the corncobs were fully mature, grain yield (GY) and biomass production (TBP) were determined. Weather conditions were recorded during the experiment. The results indicated that maximum temperature was higher and rainfall lower in the summer sowing and second year. Spring sowing had significantly higher yields of GFY, DM, GY and TBP compared to summer sowing. The first year of study showed significantly higher yields regarding GFY, GY and TBP, but FDN, FDA, DM content compared to the second year. The best hybrid for GFY and DM was Rio-Grande; for FDN and FDA was Advance 2203; for GY was HT9150W and finally for TBP was Arrayan. Regardless of the hybrid used and the sowing season, production of maize depended on external factors such as maximum temperature and rainfall; therefore, producers need to consider sowing in spring to avoid the negative effect of high temperatures on plant development.The aim was to evaluate yield of forage, grain and biomass and fibre content of eight hybrids of maize (Rio-Grande, Arrayan, Genex 778, Narro 2010, Advance 2203, DAS 2358, P4082W and HT9150W) during two sowing seasons (spring/summer) for two consecutive years at La Laguna in Torreon, Mexico. Once the grain progression of the kernel milk line was ⅓, green forage yield (GFY), dry matter (DM), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined. When the corncobs were fully mature, grain yield (GY) and biomass production (TBP) were determined. Weather conditions were recorded during the experiment. The results indicated that maximum temperature was higher and rainfall lower in the summer sowing and second year. Spring sowing had significantly higher yields of GFY, DM, GY and TBP compared to summer sowing. The first year of study showed significantly higher yields regarding GFY, GY and TBP, but FDN, FDA, DM content compared to the second year. The best hybrid for GFY and DM was Rio-Grande; for FDN and FDA was Advance 2203; for GY was HT9150W and finally for TBP was Arrayan. Regardless of the hybrid used and the sowing season, production of maize depended on external factors such as maximum temperature and rainfall; therefore, producers need to consider sowing in spring to avoid the negative effect of high temperatures on plant development

Derivada generalizada de Lanczos en una discontinuidad finita

Lanczos introdujo una expresión integral para calcular la derivada de una función, siendo ésta continua en el punto x bajo análisis, Aquí extendemos dicha expresión al caso de una discontinuidad finita en x

Effects of dietary beef tallow on performance, rumen fermentation, carcass traits and meat quality of growing lambs

Growing lambs were evaluated for the effect of increasing dietary levels of beef tallow (BT) on performance, rumen fermentation, and carcass and meat characteristics. Twenty-one 5-month-old male Rambouillet lambs were assigned randomly to one of three diets with 0, 20, and 40 g BT/kg dry matter (DM) and similar energy and protein contents. Lambs were adapted to the diets for 15 days, followed by a 45-day evaluation trial. Data were analysed using a mixed model. Growth, feed intake and ruminal fermentation were not affected by the dietary level of BT. Daily metabolizable energy intake (MEI), carcass yield and degree of fatness, increased linearly as the BT level increased. Carcass classification and muscle conformation were not affected by BT. Most meat characteristics (texture, pH, myoglobin, protein content, colour, cathepsins, and chemical composition) five and eight days post-mortem were not affected, except for fat content in meat, which increased linearly as diet BT level increased. Fatty acid (FA) profiles of the meat from lambs fed the three diets were similar. In conclusion, addition of BT at 20 and 40 g/kg DM to diets for growing lambs allowed reduced grain usage and increased forage levels (from 0 to 270 g/kg DM), increasing energy intake, carcass yield and fatness, and intramuscular fat without causing harmful effects on growth, feed intake or ruminal fermentation characteristics. Keywords: dietary fat, fatty acids, meat colour, shee

Physiological Regulation of Isocitrate Dehydrogenase and the Role of 2-Oxoglutarate in Prochlorococcus sp. Strain PCC 9511

The enzyme isocitrate dehydrogenase (ICDH; EC 1.1.1.42) catalyzes the oxidative decarboxylation of isocitrate, to produce 2- oxoglutarate. The incompleteness of the tricarboxylic acids cycle in marine cyanobacteria confers a special importance to isocitrate dehydrogenase in the C/N balance, since 2-oxoglutarate can only be metabolized through the glutamine synthetase/glutamate synthase pathway. The physiological regulation of isocitrate dehydrogenase was studied in cultures of Prochlorococcus sp. strain PCC 9511, by measuring enzyme activity and concentration using the NADPH production assay and Western blotting, respectively. The enzyme activity showed little changes under nitrogen or phosphorus starvation, or upon addition of the inhibitors DCMU, DBMIB and MSX. Azaserine, an inhibitor of glutamate synthase, induced clear increases in the isocitrate dehydrogenase activity and icd gene expression after 24 h, and also in the 2-oxoglutarate concentration. Iron starvation had the most significant effect, inducing a complete loss of isocitrate dehydrogenase activity, possibly mediated by a process of oxidative inactivation, while its concentration was unaffected. Our results suggest that isocitrate dehydrogenase responds to changes in the intracellular concentration of 2-oxoglutarate and to the redox status of the cells in Prochlorococcus

Differential expression of dnaA and dosR genes among members of the Mycobacterium tuberculosis complex under oxic and hypoxic conditions

Major differences regarding the pathology and host immune response of the Beijing and Canettii genotypes of Mycobacterium tuberculosis have been reported; however, studies on the genetic expression of these genotypes during in vitro dormancy are scarce. This study examined the expression of five cell-cycle-related genes and two dormancy-related genes in M. canettii, M. tuberculosis H37Rv, and M. tuberculosis Beijing during the Wayne model of dormancy. The results showed that under hypoxic conditions the three tuberculosis genotypes were able to transcribe genes involved in DNA replication and cellular division. In addition, dosR was found to be up-regulated in M. tuberculosis Beijing during the exponential growth phase but down-regulated under hypoxic conditions. In this genotype, the replication-related gene dnaA was also strongly down-regulated. These latter two findings suggest that, compared to M. tuberculosis H37Rv and M. canettii, the Beijing genotype has a lower capacity to synthesize dosR, hspX, and dnaA mRNAs during in vitro dormancy. [Int Microbiol 2010;13(1):9-13

A Holistic Formulation for System Margining and Jitter Tolerance Optimization in Industrial Post-Silicon Validation

There is an increasingly higher number of mixed-signal circuits within microprocessors and systems on chip (SoC). A significant portion of them corresponds to high-speed input/output (HSIO) links. Post-silicon validation of HSIO links can be critical for making a product release qualification decision under aggressive launch schedules. The optimization of receiver analog circuitry in modern HSIO links is a very time consuming post-silicon validation process. Current industrial practices are based on exhaustive enumeration methods to improve either the system margins or the jitter tolerance compliance test. In this paper, these two requirements are addressed in a holistic optimization-based approach. We propose a novel objective function based on these two metrics. Our method employs Kriging to build a surrogate model based on system margining and jitter tolerance measurements. The proposed method, tested with three different realistic server HSIO links, is able to deliver optimal system margins and guarantee jitter tolerance compliance while substantially decreasing the typical post-silicon validation time.ITESO, A.C

A Multi-Stage CTLE Design and Optimization for PCI Express Gen6.0 Link Equalization

The continuously increasing bandwidth demand from new applications has led to the development of the new peripheral component interconnect express (PCIe) Gen6, reaching data rates of 64 giga-transfers per second (GT/s) and adopting the pulse amplitude modulation 4-level (PAM4) signaling scheme. While PAM4 solves the bandwidth requirements, it brings new challenges for the physical channel design. PAM4 is more susceptible to errors due to various noise sources caused by reduced voltage (and timing) ranges, yielding a higher bit error rate (BER). It also introduces new challenges in slicers, transition jitter, and equalizers, making of equalization (EQ) a critical process for PAM4 signaling. In this paper, we propose a multi-stage continuous-time linear equalizer (CTLE) with high-band, mid-band, and low-band frequency boost stages to deal with highly lossy channels. Given the complexity of EQ of multi-level signals, optimization techniques are used, including an efficient optimization of the transmitter finite impulse response (FIR) filter and the receiver CTLE tuning.ITESO, A.C

Effect of 8-Week Consumption of a Dietary Pattern Based on Fruit, Avocado, Whole Grains, and Trout on Postprandial Inflammatory and Oxidative Stress Gene Expression in Obese People

Overweight and obesity constitute a major global public health problem. Healthy dietary patterns induce changes at the molecular level. Currently, there are no studies evaluating the effect of a diet based on fruit, avocado, whole grains, and trout (FAWGT diet) on the expression of obesity-related genes. This randomized controlled crossover study included 44 obese Colombians with BMI ≥30 kg/m2 who followed either a FAWGT diet or a usual diet (UD) characterized by a high intake of saturated fat and foods rich in processed carbohydrates. After 8 weeks of intervention, a postprandial expression study of inflammation and oxidative stress-related genes was carried out with a real-time PCR. The intervention with a FAWGT diet decreased the expression of inflammatory (NFKB1, IL6, IL1β) and oxidative stress (NFE2L2) genes compared with the intake of the UD. Finally, the postprandial expression of NFkB1 was positively correlated with triglyceride levels after a dietary intervention with the FAWGT diet and the IL1β gene, and likewise with insulin levels after following the usual diet. The consumption of the FAWGT diet for 8 weeks reduced the inflammatory status; thus, it can be considered a valid alternative to other healthy diets, since it induces beneficial changes on the genes involved in inflammation and oxidative stress in obese people