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Notes: A variational estimate of the free energy of a quantum spin chain based on the stochastic behavior of the quantization axes is proposed. It allows a description of the nonlinear excitations and quantum spin waves within the same framework.For an easy-plane ferromagnet with an external field in the plane it reveals that the nonlinear excitations (solitons) are predominantly described by the classical degrees of freedom. Considerable effort has been devoted to the theoretical description1 and experimental verification of the existence of nonlinear excitations. In this field magnetic chain systems have played an important part.2 Chain systems with an easy-plane anisotropy, such as (C6 H11 NH3 )CuBr3 (CHAB) and CsNiF3 , which are subjected to a symmetry breaking field, were found to be soliton bearing.3 Theoretically the description of the nonlinear effect is based on the mapping of the spin dynamics on a sine-Gordon model. Further research4 indicated that the interpretation of the thermodynamical properties of real systems in terms of the sine-Gordon model required however quantum and anisotropy corrections. Since the dipolar interactions between the spins in the chain are considered to be negligible, the direction of the spin chain in configuration space with respect to any preferred direction in spin space does not enter explicitly in the Hamiltonian. This makes it interesting to define a site-dependent z direction in spin space which makes an angle (aitch-thetan ,φn ) with the z direction in configuration space.The model Hamiltonian can then be written in terms of the spin operators defined with respect to the site-dependent quantization axis. The representation with equal quantization axis for all the sites is related to the representation with different quantization axes at each site by a rotation in spin space. The unitary transformation that describes the rotation contains the angles (aitch-thetan ,φn ), which we have treated as random variables. Based on this observation we have proposed a new variational approach for the quantum spin chain. We will outline the main results here. A full account is published elsewhere.5In our approach the free energy of the system can be separated in a quantum part and a classical part. The free energy F of the chain is then approximated by an upper bound F〈Fcl +Fqm , where βFcl =−ln[E(exp−βVcl )] and βFqm =−ln Tr(exp−β〈Hqm 〉). The first part is a configurational classical free energy, depending on the choice of the probability distribution for the quantization axes via the expectation E. The second contribution is the free energy of a modified quantum chain, whose parameters are classical averages and can be obtained from the configurational classical free energy. For easy-plane ferromagnetic chains, the nonlinear excitations are comprised in the classical part, whereas the quantum part contains predominantly linear excitations. For those thermodynamical quantities that are insensitive to the contribution of the quantum excitations, the chain is thermodynamically equivalent with a classical sine-Gordon system. The out-of-plane corrections are incorporated in the quantum part of the free energy. This behavior is corroborated experimentally by measurements of the excess heat capacity of CHAB for different magnetic fields with the same in-plane component.6 The validity of our approach is, however, not restricted to easy-plane ferromagnetic chains. Also for more complex systems with, for example, an orthorhombic or helical symmetry, the introduction of stochastic quantization axes can shed new light on some of the thermodynamical properties of these quantum systems in terms of their classical equivalent.

Notes: Background : Monoclonal antibodies to the pro-inflammatory cytokine tumour necrosis factor-α have shown efficacy in treating Crohn's disease, but can be immunogenic. Soluble tumour necrosis factor-binding proteins are being studied as potential alternative anti-tumour necrosis factor agents in Crohn's disease.Aim : To investigate the safety and efficacy of onercept, a recombinant form of the natural human soluble p55 tumour necrosis factor receptor, in the treatment of patients with active Crohn's disease.Methods : In a pilot study, 12 patients with active Crohn's disease were randomized to receive onercept at either 11.7 or 50 mg three times weekly for 2 weeks. Patients were followed up for 6 months after the end of treatment.Results : The Crohn's disease activity index decreased rapidly during treatment in both groups. Seven responses (Crohn's disease activity index decrease of 100 points) were observed over the first 6 weeks of the study, including five remissions (Crohn's disease activity index decrease of 150 points). Improvement was sustained for 2–4 months after stopping treatment. Treatment was well tolerated. No patients developed antibodies to onercept.Conclusions : Neutralizing the activity of tumour necrosis factor-α with its soluble p55 receptor may be valuable in the treatment of patients with Crohn's disease. Larger placebo-controlled trials are indicated.

Notes: Abstract. The CT and MRI findings in a case of chondrosarcoma of the hyoid bone are reported. Although chondrosarcoma is the second most common primary malignant bone tumor, only 10 % of chondrosarcomas occur in the head and neck region. The hyoid bone is a rare site of involvement with only seven cases reported previously.

Notes: Abstract After oral administration of rhein to rats, three rhein containing fractions were isolated from the urine: rhein, rheinmonoglucuronide and rheinmonosulphate. Rheinmonoglucuronide was identified by determination of the hydroxyanthraquinone- and the glucuronic acid component and by enzymatic cleavage withΒ-glucuronidase. Rheinmonosulphate could be split by sulphatase. Within 72 h after administering rhein to rats, only 17 to 20% anthracene derivatives could be recovered from the faeces and urine.

Notes: Abstract The metabolic pathway of sennoside A and B in tied-off gastrointestinal segments of the rat was investigated. The excretion of anthracene derivatives in urine and faeces of the rat after oral administration of the glycosidic compounds has also been studied. For the quantitative determination of rhein in biological samples, a densitometric method on thin-layer chromatograms has been developed. Sennoside A and B seem to be hydrolyzed by the intestinal microorganisms into the aglycones sennidin A and B, which in turn are metabolised into rhein-9-anthrone and rhein. These metabolites are excreted with the faeces. In the urine, sennidin, rhein and rheinmonoglucuronide were found.