Diffraction theory and focusing of light by left-handed materials

A diffraction theory in a system consisting of left-handed and right-handed materials is proposed. The theory is based upon the Huygens's principle and the Kirchhoff's integral and it is valid if the wavelength is smaller than any relevant length of the system. The theory is applied to the calculation of the smearing of the foci of the Veselago lens due to the finite wavelength. We show that the Veselago lens is a unique optical instrument for the 3D imaging, but it is not a ``superlens'' as it has been claimed recently.Comment: 7 pages, 2 figure

Annotated bibliography on the economic effects of global climate change on fisheries

Fisheries, Bibliography, Climatic changes

Prevalence Of Bruxism And Emotional Stress And The Association Between Them In Brazilian Police Officers

This study aimed to assess the prevalence of bruxism and emotional stress in Brazilian police officers, due to exposure to stressful situations, and to assess the relationship between the type of work done by a police officer and the presence of bruxism and emotional stress. A cross-sectional study was conducted at the Military Police of the State of São Paulo, Campinas, SP, Brazil. The final sample included 394 male police officers (mean age = 35.5 years). Bruxism was diagnosed by the presence of aligned dental wear facets associated with the presence of one of the following signs or symptoms: self-report of tooth-grinding, painful sensitivity of the masseter and temporal muscles, discomfort in the jaw musculature upon waking. The Stress Symptoms Inventory (SSI) was applied to evaluate emotional stress. The type of work done by the police was classified as organizational or operational, the latter being assumed as the more stressful since it exposes the police officer to life risk. The results showed a prevalence of bruxism of 50.2% and a prevalence of emotional stress of 45.7%. The Chi-square test indicated an association between stress and bruxism (P < .05). No significant association was found between emotional stress and type of work (P = .382) or between bruxism and work activity (P = .611). It could be concluded that emotional stress was associated with bruxism, independently of the type of work done by police officers.2213135Lavigne, G.J., Rompré, P.H., Montplaisir, J.Y., Sleep bruxism: Validity of clinical research diagnostic criteria in a controlled polysomnographic study (1996) J Dent Res, 75 (1), pp. 546-552Lobbezoo, F., Naeije, M., Bruxism is mainly regulated centrally, not peripherally (2001) J Oral Rehabil, 28 (12), pp. 1085-1091Arnold, A., Bruxism and the occlusion (1981) Dent Clin North Am, 25, pp. 395-407Rugh, J.D., Harlan, J., Nocturnal bruxism and temporoman-dibular disorders (1988) Adv Neurol, 49, pp. 329-341Tsai, C.M., Chou, S.L., Gale, E.N., McCall Jr, W.D., Human masticatory muscle activity and jaw position under experimental stress (2002) J Oral Rehabil, 29 (1), pp. 44-51Manfredini, D., Landi, N., Romagnoli, M., Bosco, M., Psychic and occlusal factors in bruxers (2004) Aust Dent J, 49 (2), pp. 84-89Pingitore, G., Chrobak, V., Petrie, J., The social and psychologic factors of bruxism (1991) J Prosthet Dent, 65 (3), pp. 443-446Watanabe, T., Ichikawa, K., Clark, G.T., Bruxism levels and daily behaviors: 3 weeks of measurement and correlation (2003) J Orofac Pain, 17 (1), pp. 65-73Pierce, C.J., Chrisman, K., Bennett, M.E., Close, J.M., Stress, anticipatory stress, and psychologic measures related to sleep bruxism (1995) J Orofac Pain, 9 (1), pp. 51-56Axelbend, M., Vaile, J., South Florida's approach to police stress management (1979) Police Stress, 1, pp. 13-14Blackmore, J., (1978) Are police allowed to have problems of their own? Police Mag, 1, pp. 47-55Violanti, J.M., (1996) Police suicide: Epidemic in blue, , Springfield: Charles C Thomas;Neylan, T.C., Metzler, T.J., Best, S.R., Weiss, D.S., Fagan, J.A., Libermam, A., Critical incident exposure and sleep quality in police officers (2002) Psychosom Med, 64 (2), pp. 345-352Lipp, M.E.N., Guevara, A.J.H., Empiric validation of stress symptoms inventory (SSI) (1994) Estud Psicol, 11, pp. 43-49Pigno, M.A., Hatch, J.P., Rodrigues Garcia, R.C., Sakai, S., Rugh, J.D., Severity, distribution, and correlates of occlusal tooth wear in a sample of Mexican-American and European-American adults (2001) Int J Prosthodont, 14 (1), pp. 65-70Glaros, A.G., Incidence of diurnal and nocturnal bruxism (1981) J Prosthet Dent, 45 (5), pp. 545-549Ramfjord, S.P., Bruxism, a clinical and electromyographic study (1961) J Am Dent Assoc, 62, pp. 21-44Manfredini, D., Ciapparelli, A., Dell'Osso, L., Bosco, M., Mood disorders in subjects with bruxing behavior (2005) J Dent, 33 (6), pp. 485-490Manfredini, D., Landi, N., Fantoni, F., Segù, M., Bosco, M., Anxiety symptoms in clinically diagnosed bruxers (2005) J Oral Rehabil, 32 (8), pp. 584-588Wigdorowicz-Makowerowa, N., Epidemiological studies on prevalence and etiology of functional disturbances of the masticatory system (1979) J Prosthet Dent, 41 (1), pp. 76-82Collins PA, Gibbs ACC. Stress in police officers: a study of the origins, prevalence and severity of stress-related symptoms within a county police force. Occup Med. 2003;53(4):256-64Bültmann, U., Kant, I., Kasl, S.V., Beurskens, A.J., van der Brandt, P.A., Fatigue and psychological distress in the working population: Psychometrics, prevalence, and correlates (2002) J Psychosom Res, 52 (6), pp. 445-452Spielberg, C.C., Westberry, L.G., Grier, K.S., Greenfield, G., (1981) The police stress survey: Sources of stress in law enforcement, , Tampa FL, Human Resources Institute;Kirkcaldly, B., Cooper, C.L., Ruffalo, P., Work stress and health in a sample of U.S. police (1995) Psychol Rep, 76 (2), pp. 700-702Kroes, W.H., Gould, S., Job stress in policemen: An empirical study (1979) Police Stress, 1, pp. 9-10Violanti, J.M., Aron, F., Ranking police stressors (1994) Psychol Rep, 75 (2), pp. 824-826Violanti, J.M., Aron, F., Sources of police stressors, job attitudes and psychological distress (1993) Psychol Rep, 72 (3 PART 1), pp. 899-90

Rigidity and Vanishing Theorems for Almost Even-Clifford Hermitian Manifolds

We prove the rigidity and vanishing of several indices of ''geometrically natural'' twisted Dirac operators on almost even-Clifford Hermitian manifolds admitting circle actions by automorphisms

Quantitative trait loci mapping for resistance to maize streak virus in F2: 3 population of tropical maize

Open Access Article; Published online: 01 Feb 2020Maize streak virus (MSV) continues to be a major biotic constraint for maize production throughout Africa. Concerning the quantitative nature of inheritance of resistance to MSV disease (MSVD), we sought to identify new loci for MSV resistance in maize using F2:3 population. The mapping population was artificially inoculated with viruliferous leafhoppers under screenhouse and evaluated for MSVD resistance. Using 948 DArT markers, we identified 18 quantitative trait loci (QTLs) associated with different components of MSVD resistance accounting for 3.1–21.4% of the phenotypic variance, suggesting that a total of eleven genomic regions covering chromosomes 1, 2, 3, 4, 5 and 7 are probably required for MSVD resistance. Two new genomic regions on chromosome 4 revealed the occurrence of co-localized QTLs for different parameters associated with MSVD resistance. Moreover, the consistent appearance of QTL on chromosome 7 for MSVD resistance is illustrating the need for fine-mapping of this locus. In conclusion, these QTLs could provide additional source for breeders to develop MSV resistance

Dielectric photonic crystal as medium with negative electric permittivity and magnetic permeability

We show that a two-dimensional photonic crystal (PC) made from a non-magnetic dielectric is a left-handed material in the sense defined by Veselago. Namely, it has negative values of both the electric permittivity $\epsilon$ and the magnetic permeability $\mu$ in some frequency range. This follows from a recently proven general theorem. The negative values of $\epsilon$ and $\mu$ are found by a numerical simulation. Using these values we demonstrate the Veselago lens, a unique optical device predicted by Veselago. An approximate analytical theory is proposed to calculate the values of $\epsilon$ and $\mu$ from the PC band structure. It gives the results that are close to those obtained by the numerical simulation. The theory explains how a non-zero magnetization arises in a non-magnetic PC.Comment: 11 pages 4 figure

Changes in the UK baby food market surveyed in 2013 and 2019: the rise of baby snacks and sweet/savoury foods

Objective: To assess how the baby food market in the UK has changed between 2013 and 2019. Setting: United Kingdom. Design: A cross-sectional survey of all infant food products available to buy in the UK online and in-store collected in 2019. Nutritional content and product descriptions were recorded and compared with an existing 2013 database. Main outcome measures: Change in the proportion of products marketed to infants aged 4 months, proportion classified as sweet versus savoury, spoonable versus dry (snacks) average sugar content. Results: Fewer products were described as suitable for infants aged 4 months in 2019 (201, 23%) compared with 2013 (178, 43%; p&lt;0.001), while the proportion for children in the 6–7-month age range increased (2013: 135, 33%; 2019: 369, 43%; p=0.001). The proportion of sweet and savoury products was unchanged; sweet spoonable products showed a small but significant decrease in sugar content (6%) between 2013 and 2019, but savoury spoonable products showed a 16% increase. Sweet snacks remained very sweet (~20 g/100 g median sugar at both time points). In the 2019 dataset, concentrated juice was added to 29% (n=253) of products and 18% (n=80) ‘savoury’ products comprised more than 50% sweet vegetables or fruit. The number and proportion of snacks increased markedly in 2019 (185, 21%) compared with 2013 (42, 10%; p=0.001) while the proportion of wet spoonable foods decreased (2013: 326, 79%; 2019: 611, 71%; p=0.001). Conclusions: Fewer foods are now marketed to infants aged 4 months, but there has been no overall reduction in the sweetness of products and the increase in snack foods and the sweetness of savoury foods is a concern