Electronic and magnetic properties of Mn-doped BeSiAs(2) and BeGeAs(2) compounds.

The structural, electronic and magnetic properties of BeSiAs(2) and BeGeAs(2) chalcopyrite ternary compounds doped with manganese were investigated by means of ab initio calculations. It was found that substitution of Be atoms by Mn increases the lattice constants of both compounds that provide acceptable mismatch with conventional Si, Ge and GaAs substrates. In spite of the increase of the spin polarization upon doping, both compounds possess antiferromagnetic (AFM) ordering with the impurity in the group II position whereas ferromagnetic (FM) ordering is obtained in the case of an impurity in the group IV position.

[The excitation of the fibers of the funiculus dorsalis medullae spinalis during the stimulation of different groups of cutaneous and muscle nerve fibers in the cat]. / Vozbuzhdenie volokon dorsal'nykh kanatikov spinnogo mozga pri razdrazhenii razlichnykh grupp volokon kozhnogo i myshechnogo nervov koshki.

Electric stimulation of various groups of fibres of cutaneous and muscle nerve of cat has been studied for its effect on action potentials in the gray dorsal column fibres, Registration was performed at the level L2--L3 from ipsi- and contralateral dorsal columns, using needle electrodes. Action potentials of dorsal columns, arisen by stimulation of cutaneous nerves, had a more complex form than those of stimulated muscle nerves. Nonmyelinated fibres of a cutaneous nerve are shown to relate to those of dorsal columns. Excitation of high-threshold A- and C-fibres activates the most fast-conducting fibres of dorsal columns. When a stimulus was applied to all fibres of the cutaneous nerve, the action potentials with conduction velocities of 146-0.24 m/s were recorded in dorsal columns. It was shown that such conduction velocities remained in dorsal columns to level C7. Stimulation of muscle nerves excited only myelinic fibres of dorsal columns, the conduction velocities ranging from 90 to 2.3 m/s. By alternating stimulation of either nerve with a 30-300 ms interval we decreased the action potential amplitude of the nerve that was the second to be stimulated. It is likely be related to convergence of the cutaneous and muscle nerve inputs in the spinal cord on the same neurons. A suggestion is made that faster transfer of high-threshold cutaneous signals in dorsal column are associated with the necessity of rapid information about damaging stimulation.

[Reaction of nonmyelinated fibers of the cutaneous nerve of cats to cooling]. / Aktivnost' v bezmielinovykh voloknakh kozhnogo nerva koshki v otvet na okhlazhdenie.

Combining the colliding impulses method with the methods of singling out the nerve's weak signals from the equipment noise shows that most nonmyelinated fibers of C1 and C2 groups develop impulses under cooling the cat hairy skin. In some nonmyelinated fibers of the C2 group there takes place an inhibition of spontaneous impulses in response to cooling.

[Do specialized cutaneous cold receptors exist?]. / Sushchestvuiut li spetsializirovannye kholodovye retseptory kozhi?

The relative quantity of the cutaneous nerve unmyelinated fibers that conduct the excitation impulses from mechanoreceptors under contraction of pilomotors without and during cooling of the skin by 10 degrees C at a rate of 1 degree C per second was measured by the integrating method of colliding impulses. The same mechanoreceptors are shown to be excited by pilomotors both under skin deformation and cooling. A conclusion is made about absence of specific cold receptors in the cat skin.

[Distribution of the bone marrow cells in the skeleton of mice]. / Raspredelenie kletok kostnogo mozga v skelete myshei.

The data on the content of nucleated bone marrow cells in 17 skeletal portions of the hybrid F1 (CBA X C57B1) laboratory mice weighing 18-21 g are presented. The bone marrow content in the bones of the spine, head, inferior limb, pelvis, upper limb, sternum and ribs constituted 33.7; 19.6; 17.6; 11.9; 8.2 and 9.0% of the total amount, respectively. The epxerimental results are compared with the literature data.

[Activity in the myelin fibers of the cat cutaneous nerve in response to heating]. / Aktivnost' v mielinovykh voloknakh kozhnogo nerva koshki v otvet na nagrevanie.

The collision method combined with some techniques improving the signal-to-noise ratio showed that the activation in the nerve fiber group A gamma 1, A delta, A delta 2 and in "mixed" fibers group was changed by hairy skin heating. A relatively great number of nerve fibers of these groups were activated and only an insignificant part of them inhibited their activity in response to the cutaneous receptor heating. A spontaneous activity increase and skin relaxation under heating. were shown.

[Activity in the myelinated fibers of a cat cutaneous nerve in response to cooling]. / Aktivnost' v mielinovykh voloknakh kozhnogo nerva koshki v otvet na okhlazhdenie.

The afferent activation in cat cutaneous nerve fibres in response to cooling was analyzed using the collision method and the method improving the signal-to-noise ratio in the antidromic action potential neurogram. It was found that the nerve fibres of groups Adelta1 and Adelta2 were activated under cutaneous receptors cooling. The activity of a small group of nerve fibres with conduction velocity 13.0--7.5 m/s was inhibited in response to cooling. A group of "mixed" fibres inhibited mainly its activity, but only an insignificant part of these fibres activated in response to cutaneous receptors cooling.

[Afferent activity in fine myelinated and unmyelinated nerve fibers of a cutaneous nerve upon mechanical stimulation of cutaneous receptors]. / Afferentnaia aktivnost' v tonkikh mielinizirovannykh i nemielinizirovannykh nervnykh voloknakh kozhnogo nerva pri mekhanicheskikh razdrazheniiakh retseptorov kozhi

The activity in fine myelinated and nonmyelinated nerve fibres of a cat cutaneous nerve was analyzed using a collision method and method improving the signal-to-noise ratio in the antidromic action potential neurogram. On the basis of the investigation of conduction velocities, electrical excitation thresholds and responses to mechanical stimulations, the following groupsare distinguished among fine myelinated and nonmyelinated fibres: group A delta1 (30-14m/s) activated mostly under light mechanical stimulation; group A delta2 (14.4.0 m/s) more readily activated by intense mechanical stimulation; group of "mixed" fibres containing myelinated and nonmyelinated nerve fibres (4-2 m/s) activated under both kinds of mechanical stimulation; group C1 (2.0-1.0 M/S) ACTIVATED MOSTLY BY LIGHT Mechanical stimulation and group C2 (1.0-0.15 M/S) CONNECTED WITh receptors that require for excitation intense mechanical stimulation.

Analysis of activity in A and C fibres under mechanical and thermal stimulation of the skin receptor field.

A conduction velocity spectrum in nerve fibres of 0.15 to 90 m/sec was found by means of electrophysiological methods of analysis and computer-aided processing of experimental data. A greater portion of the non-myelinated fibres in the cutaneous nerve proved to be afferent. Patterns of afferent impulse flows entering the central nervous system are determined under various mechanical and thermal stimulations of cat's cutaneous receptive field. Differences of these flows are considered to be the reasons for various sensation modalities. The mechanism of cutaneous mechanoreceptor excitation under temperature stimuli is discussed. Special attention is paid to the contraction of cutaneous collagen under cooling. Experimental data on the change of cutaneous mechanical properties and the electrophysiological changes corroborating the thermomechanical hypothesis of receptor excitation are given.

[Spinal nerve root distribution of the myelinated and unmyelinated nerve fibers of a cat cutaneous nerve]. / Raspredelenie v koreshkakh spinnogo mozga mielinizirovannykh i nemielinizirovannykh nervnykh volokon kozhnogo nerva koshki

The distribution of myelinated and nomyelinated nerve fibres from n. saphenus in the dorsal and ventral roots of the cat spinal cord was investigated, using methods improving the signal-to-noise ratio in the neurogram of the nerve evoked response. Nerve fibres from n. saphneus enter the spinal cord through roots of segments L4-6. In the dorsal roots of these segments the nerve fibres have conduction velocities from 80 to 0.38 m/s. In the ventral roots four groups of the nerve fibres with conduction velocities 80--60, 40--30, 12.0--3.0 and 1.1--0.51 m/s are found that are likely to be afferents. The conditions for low amplitude potentials detection in the spinal cord roots as well as the possible functional significance of the nerve fibres in the ventral roots are discussed.