The effects of lack of movement in sows during pregnancy period on cortisol, acute phase proteins and lymphocytes proliferation level in piglets in early postnatal period.

Prolonged exposure to stress may cause adverse effects on animal physiology. It is especially important during the gestation period as female physiology can affect the unborn offspring in the form of prenatal stress. Intensive pig farming industry developed gestation crates that enable to keep sows during gestation period in small stalls which do not allow animals to move freely for a maximum of 4 weeks after successful insemination (Council Directive 2008/120/EC). Although these crates have production advantages, many health and welfare issues have been raised recently. In this study we tested to what extent the lack of movement of sows kept in the gestation crates had an impact on some blood and saliva constituents of new-born piglets. In total, the samples were collected from 80 piglets when they were 3, 7 and 21 days of age and tested for cortisol levels in blood and saliva, acute phase proteins (amyloid A, C-reactive protein, haptoglobin) and lymphocytes proliferation index (in response to ConA, PHA and PWM). 40 piglets were from sows kept in free movement housing (FM group) from day 1 to day 100 of pregnancy and forty piglets were from sows in the movement restriction group (MR), in which the sows were kept in crates just allowing them to stand up and lie down from day 1 to day 100 of the pregnancy (research was conducted before the implementation Directive 2008/120/EC i.e. January 1,2013). The results of the study showed that the piglets delivered by sows kept under movement restriction conditions exhibited higher cortisol and acute phase protein levels as well as a lower lymphocytes proliferation index. This suggests that lack of movement in sows during the gestation period influences piglets' physiology and indicates that the piglets are suffering from prenatal stress caused by insufficient housing conditions of their mothers potentially leading to poor health and welfare of their offspring.

Influence of lycopene and astaxanthin in feed on metabolic parameters of laying hens, yolk color of eggs and their content of carotenoids and vitamin A when stored under refrigerated conditions.

Orientating investigations were carried out in order to test the influence of oil extracts of lycopene (20, 40 and 60 mg/kg feed) and astaxanthin (10, 20 and 30 mg/kg feed) as feed additives on the metabolic parameters (glucose, creatinine, cholesterol) and enzyme activities (alanine aminotransferase, ALT; aspartate transaminase, AST) of laying hens. Eggs from these hens were stored at refrigerator temperatures of 4°C and 12°C for up to 30 days and analyzed for vitamin A, carotenoid and yolk color. 45 laying hens (Hy-Line W36 cross, 23 weeks of age) were divided in three groups of 15 birds each (control, lycopene fed group, astaxanthin fed group). Blood samples were taken from the hens and laid eggs were collected on days 31, 61, and 91 of the study. The eggs were stored for 30 days in refrigerators. Both lycopene and astaxanthin increased the content of glucose in serum (Р⟨0.05). The content of creatinine and cholesterol, and the activity of ALT, AST and alkaline phosphatase varied dose-dependently. With the exception of cholesterol, metabolite concentrations in the serum of laying hens fed different lycopene and astaxanthin doses did not exceed clinically accepted physiological levels. The carotenoid content and color of the egg yolks from laying hens fed astaxanthin was significantly higher (Р⟨0.05) compared to lycopene fed birds. Refrigerator storage of the eggs did not affect carotenoid content and egg yolk color compared to freshly laid eggs. Both feed additives showed a favorable effect on the metabolism of laying hens and the enrichment of egg yolks with carotenoids, astaxanthin significantly more (Р⟨0.05) than lycopene.

Gate-tunable large magnetoresistance in an all-semiconductor spin valve device.

A large spin-dependent and electric field-tunable magnetoresistance of a two-dimensional electron system is a key ingredient for the realization of many novel concepts for spin-based electronic devices. The low magnetoresistance observed during the last few decades in devices with lateral semiconducting transport channels between ferromagnetic source and drain contacts has been the main obstacle for realizing spin field effect transistor proposals. Here, we show both a large two-terminal magnetoresistance in a lateral spin valve device with a two-dimensional channel, with up to 80% resistance change, and tunability of the magnetoresistance by an electric gate. The enhanced magnetoresistance is due to finite electric field effects at the contact interface, which boost spin-to-charge conversion. The gating scheme that we use is based on switching between uni- and bidirectional spin diffusion, without resorting to spin-orbit coupling. Therefore, it can also be employed in materials with low spin-orbit coupling.

Electrical spin injection and detection in high mobility 2DEG systems.

In this review paper we present the current status of research related to the topic of electrical spin injection and detection in two-dimensional electron gas (2DEG) systems, formed typically at the interface between two III-V semiconductor compounds. We discuss both theoretical aspects of spin injection in case of ballistic transport as well as give an overview of available reports on spin injection experiments performed on 2DEG structures. In the experimental part we focus particularly on our recent work on all-semiconductor structures with a 2DEG confined at an inverted GaAs/(Al,Ga)As interface and with a ferromagnetic semiconductor (Ga,Mn)As employed as a source of spin-polarized electrons.

Electrical spin injection into high mobility 2D systems.

We report on spin injection into a high mobility 2D electron system confined at an (Al,Ga)As/GaAs interface, using (Ga,Mn)As Esaki diode contacts as spin aligners. We measured a clear nonlocal spin valve signal, which varies nonmonotonically with the applied bias voltage. The magnitude of the signal cannot be described by the standard spin drift-diffusion model, because at maximum this would require the spin polarization of the injected current to be much larger than 100%, which is unphysical. A strong correlation of the spin signal with contact width and electron mean free path suggests that ballistic transport in the 2D region below ferromagnetic contacts should be taken into account to fully describe the results.

Demonstration of the spin solar cell and spin photodiode effect.

Spin injection and extraction are at the core of semiconductor spintronics. Electrical injection is one method of choice for the creation of a sizeable spin polarization in a semiconductor, requiring especially tailored tunnel or Schottky barriers. Alternatively, optical orientation can be used to generate spins in semiconductors with significant spin-orbit interaction, if optical selection rules are obeyed, typically by using circularly polarized light at a well-defined wavelength. Here we introduce a novel concept for spin injection/extraction that combines the principle of a solar cell with the creation of spin accumulation. We demonstrate that efficient optical spin injection can be achieved with unpolarized light by illuminating a p-n junction where the p-type region consists of a ferromagnet. The discovered mechanism opens the window for the optical generation of a sizeable spin accumulation also in semiconductors without direct band gap such as Si or Ge.

Proximity induced enhancement of the Curie temperature in hybrid spin injection devices.

We investigate the increase of the Curie temperature T(C) in a lateral spin injection geometry where the ferromagnetic (Ga,Mn)As injector and detector contacts are capped by a thin iron film. Because of interlayer coupling between Fe and (Ga,Mn)As T(C) gets enhanced by nearly 100% for the thinnest (Ga,Mn)As films. The use of the proximity effect might pave the way for practical implementation of spintronic devices.

Spin-blockade spectroscopy of a two-level artificial molecule.

Coulomb- and spin-blockade spectroscopy investigations have been performed on an electrostatically defined "artificial molecule" connected to spin polarized leads. The molecule is first effectively reduced to a two-level system by placing both constituent atoms at a specific location of the level spectrum. The spin sensitivity of the conductance enables us to identify the electronic spin states of the two-level molecule. We find in addition that the magnetic field induces variations in the tunnel coupling between the two atoms. The lateral nature of the device is evoked to explain this behavior.

Collapse of the spin-singlet phase in quantum dots.

We present experimental and theoretical results on a new regime in quantum dots in which the filling factor two-singlet state is replaced by new spin polarized phases. We make use of spin blockade spectroscopy to identify the transition to this new regime as a function of the number of electrons. The key experimental observation is a reversal of the phase in the systematic oscillation of the amplitude of Coulomb blockade peaks as the number of electrons is increased above a critical number. It is found theoretically that correlations are crucial to the existence of the new phases.