A bicycle can be self-stable without gyroscopic or caster effects

A riderless bicycle can automatically steer itself so as to recover from falls. The common view is that this self-steering is caused by gyroscopic precession of the front wheel, or by the wheel contact trailing like a caster behind the steer axis. We show that neither effect is necessary for self-stability. Using linearized stability calculations as a guide, we built a bicycle with extra counter-rotating wheels (canceling the wheel spin angular momentum) and with its front-wheel ground-contact forward of the steer axis (making the trailing distance negative). When laterally disturbed from rolling straight, this bicycle automatically recovers to upright travel. Our results show that various design variables, like the front mass location and the steer axis tilt, contribute to stability in complex interacting ways.     

Livelihoods and agro-ecological gradients: A meso-level analysis in the Indo-Gangetic Plains, India

Rice-wheat systems in the Indo-Gangetic Plains (IGP) have long exemplified South Asia’s agricultural transformation through the Green Revolution. The same systems now also typify the post-Green Revolution stagnation and equity challenges, despite receiving considerable attention from the research and development (R&D) community. The apparent homogeneity of vast irrigated plains masks significant diversity in assets, livelihood strategies and livelihood outcomes. The paper analyzes the rural livelihoods and underlying agro-ecological gradients in the IGP drawing on village surveys and secondary data as characterization tools. The contribution of the paper is twofold: (i) new knowledge of the socio-economic circumstances in farming communities across the Indian IGP to enhance the effectiveness and efficiency of R&D interventions and particularly poverty alleviation; and (ii) an illustration of a novel approach to operationalize livelihood analysis at the meso-level so as to address spatial scale issues and link micro-level contextual realities across a vast geographical area. The agricultural R&D community needs to incorporate this socio-economic diversity more proactively into its R&D agenda if it is to succeed in sustaining productivity gains, improving rural livelihoods equitably, and securing environmental sustainability in this important eco-region.     

Internal validation of a computerized systems model for health management decision support in growing hogs

A study was designed to conduct an internal validation of a computerized systems model for health management decision support in growing hogs. Evaluation focused on both the alpha-beta tracker, which was employed to predict underlying system variables, and the simulation model itself, which predicted system performance. Both mean absolute prediction error and Theil's u₂ statistic were calculated. Simulation scenarios were designed to highlight specific aspects of the model. In addition, a case example was developed to demonstrate the model's logical consistency and its applicability for assessing the economics of health management decisions. Use of the alpha-beta tracker to project data series, including pig deaths and disease prevalence rates at slaughter, was largely unsuccessful. The model consistently predicted hogs marketed such that 0 < u₂ < 1. Also, decreased disease rates improved both physical and financial performance as expected. Depending on the quarter involved, the maximum bid to achieve a 50% decrease in the prevalence rates of pneumonia at slaughter and a 10% decrease in the prevalence rates of atrophic rhinitis at slaughter ranged from $0.15 to $0.37 per hog marketed for one producer. Future validation efforts should emphasize data quality and the effects of disease on production while seeking system application in a commercial production setting.     

Bluetongue virus seropositivity in sheep flocks in North West Frontier Province, Pakistan

The objectives of this study were to describe the prevalence and distribution of serum antibodies to Bluetongue virus (BTV) in a sample of 38 sheep flocks in northern areas of the North West Frontier Province of Pakistan and to identify demographic and productivity variables that are associated with BTV seropositivity. Blood samples were taken from a random sample of ewes in each flock in April 1995. The owners of the flocks were interviewed regarding some demographic, husbandry and productivity variables of the flocks on the day of blood sampling. A competitive enzyme-linked immunosorbent assay was conducted to test the serum samples for BTV group-specific antibodies. BTV seropositive reactions were obtained in 184 (48.4%) out of 380 tested sera, and in 89.5% (34/38) of the flocks. In the 34 seropositive flocks, the prevalences ranged from 12.5 to 100% (median = 47). A multivariable logistic analysis was carried out to study the influence of demographic and productivity variables on the BTV serological status of the sheep flocks. Abortion risk in the previous lambing season was mildly associated with the serological status of the flock (adjusted odds ratio = 1.16, P = 0.07). For the seropositive flocks, a linear multiple regression showed that distance travelled by the flock during transhumant movement was significantly associated with percent seropositivity (partial regression coefficient (± SE) = − 0.091 ± 0.045).     

Deposition rates and accretion patterns of intramuscular fat, loin muscle area, and backfat of Duroc pigs sired by boars from two time periods

A study was conducted to evaluate differences in performance and in carcass composition and tissue deposition rates between purebred Duroc pigs sired by boars currently available and those sired by boars from the mid-1980s. Two lines were developed by randomly allocating littermate and half-sib pairs of females to matings by current time period (CTP) or old time period (OTP) boars. Pigs from 2 replications were placed on test at a group mean BW of 63.5 kg. Serial ultrasonic measurements of the 10th-rib LM area (LMA), off-midline backfat (BF10), and intramuscular fat percentage (IMF) were collected every 2 wk in the first replication and used to assess deposition rate differences. Off-test ultrasonic LMA, BF10, and IMF measurements from a total of 557 pigs from 23 CTP sires and 232 pigs from 15 OTP sires across 2 replications and at a mean BW of 109 kg were evaluated. All available barrows and randomly selected gilts (n = 277) were sent to a commercial abattoir, and carcass measurements of 10th-rib backfat, last-rib backfat, last lumbar backfat, and LMA were collected. Analysis of serial backfat measurements revealed a linear relationship between back-fat and BW between 73 and 118 kg for pigs from both time periods. Pigs sired by OTP boars deposited more backfat (P < 0.05) at a faster rate than pigs sired by CTP boars over the entire test period. A curvilinear cumulative tissue deposition pattern was revealed for ultrasonically estimated LMA and IMF within both time periods. Significant linear and quadratic regression coefficient differences between lines indicated that pigs sired by CTP boars deposited more LMA and less IMF per kilogram of BW gain than pigs sired by OTP boars. Pigs sired by CTP boars had more LMA and less BF10 (P < 0.05), whereas pigs sired by OTP boars had more IMF (P = 0.04). Carcass evaluation revealed more (P < 0.01) carcass measurements of LMA and less (P < 0.05) carcass measurements of 10th-rib backfat, carcass measurements of last-rib backfat, and carcass measurements of last lumbar backfat for pigs sired by CTP boars. No difference (P > 0.05) between the time periods was found for ADG over the entire test period. Results from this study illustrate that significant progress in carcass composition has been realized within the Duroc breed since the mid-1980s. The long-term selection response in carcass leanness has also resulted in changes in deposition rates of correlated traits such as LMA and IMF.     

Die Grundlagen des natürlichen Erdbeeraromas

Due to its abundance of taste and odour compounds the strawberry becomes more and more popular. But what makes the flavour of this fruit so extraordinary? Scientists from the Technische Universität München (TUM) provide an answer. They succeeded in the elucidation of the formation pathway of a key aroma chemical of strawberry fruit on the molecular level.     

Promotion of lymphocyte egress into blood and lymph by distinct sources of sphingosine-1-phosphate

Lymphocytes require sphingosine-1-phosphate (S1P) receptor-1 to exit lymphoid organs, but the source(s) of extracellular S1P and whether S1P directly promotes egress are unknown. By using mice in which the two kinases that generate S1P were conditionally ablated, we find that plasma S1P is mainly hematopoietic in origin, with erythrocytes a major contributor, whereas lymph S1P is from a distinct radiation-resistant source. Lymphocyte egress from thymus and secondary lymphoid organs was markedly reduced in kinase-deficient mice. Restoration of S1P to plasma rescued egress to blood but not lymph, and the rescue required lymphocyte expression of S1P-receptor-1. Thus, separate sources provide S1P to plasma and lymph to help lymphocytes exit the low-S1P environment of lymphoid organs. Disruption of compartmentalized S1P signaling is a plausible mechanism by which S1P-receptor-1 agonists function as immunosuppressives.