bluuebunny/crossref_metadata_2025 huggingface dataset:
Caring for a child with cancer—A systematic review
Authors: Vance Yvonne , Eiser Christine
Published: January 2004

Objective

To report the results of a systematic review to determine the effects of parents' behavior on children's coping with cancer.

Methods

Searches were conducted using Medline, EMBASE, PsycLit, and articles were subsequently selected on the basis of predefined criteria.

Results

Twenty‐four papers were identified. There were associations between parenting behaviors and child distress both before and during medical procedures. Parents who criticized the child, or apologized for what was happening had children who were more distressed. Parents who were very permissive had more problems with adherence to treatment regimens.

Conclusions

Parents' behavior is critical in determining children's responses during procedures and adherence to home care. There has been less work concerning how parents manage more everyday problems, such as encouraging the child to go to school. Longitudinal studies are recommended to determine how parenting behaviors affect longer term child adjustment. These findings may be helpful for clinic staff to understand parents' reactions, and may also inform the content of intervention programs. © 2003 Wiley‐Liss, Inc.
Association of cytogenetic abnormalities with detection of BCR‐ABL fusion transcripts in children with T‐lineage lymphoproliferative diseases (T‐ALL and T‐NHL)
Authors: Lo Nigro Luca , Sainati Laura , Mirabile Elena , Lanciotti Marina , Poli Amelia , Leszl Anna , Basso Giuseppe
Published: January 2004

Detection of Philadelphia chromosome (Ph) in childhood T‐lineage acute lymphoproliferative disorders is a rare event. Additional cytogenetic abnormalities are particularly uncommon in ALL. We here report two cases with T lineage acute lymphoproliferative disorders (T‐ALL and T‐NHL) presenting with both cytogenetic alterations and BCR‐ABL fusion transcripts, associated with an aggressive presentation and a poor outcome. We point out firstly on the cytogenetic aberrations, supporting the hypothesis of multi‐lineage involvement of ALL expressing Ph chromosome; secondly, on the persistence of T‐cell leukemic clone detected by minimal residual disease (MRD) analysis, despite of the early disappearance of BCR‐ABL fusion transcript. © 2003 Wiley‐Liss, Inc.
Biodistribution of post‐therapeutic versus diagnostic 131I‐MIBG scans in children with neuroblastoma
Authors: Hickeson Marc P. , Charron Martin , Maris John M. , Brophy Patricia , Kang Tammy I. , Zhuang Hongming , Khan Jehanzeb , Nevrotski Teresa
Published: January 2004

Background

To evaluate the biodistribution of therapeutic 131I‐metaiodobenzylguanidine (MIBG) and assess the sensitivity of diagnostic versus therapeutic 131I‐MIBG scans to detect metastatic disease.

Procedure

This retrospective study included 44 diagnostic and post‐therapy scans (PTS) in 18 children with neuroblastoma treated with 131I‐MIBG (2.0–33.1 GBq). The findings of diagnostic scans (DS) (2.6–44.4 MBq) were compared to those of corresponding PTS.

Results

In terms of biodistribution, the PTS identified 131I‐MIBG activity in one or more patients in the following regions not detected on the DS: nasal mucosa, cerebellum, central brain, adrenals, spleen, kidneys, thyroid, salivary glands, lower halves of the lungs, bladder, bowel, and an incisional scar. Conversely, the DS identified activity in the thorax, heart, kidneys, and bladder each in one patient without being visualized on the PTS. In terms of sensitivity to detect metastatic disease, 210 lesions were seen on the PTS compared to 151 on the DS. The PTS demonstrated sites of disease not evident in the DS in 16 cases.

Conclusions

The biodistribution of 131I‐MIBG is different using therapeutic doses as compared to pre‐therapy doses. 131I‐MIBG imaging following high therapeutic doses often reveals sites of occult metastatic disease that may be clinically relevant. © 2003 Wiley‐Liss, Inc.
Middle cerebral artery Doppler velocimetric assessment in two cases of hydrops fetalis without fetal anaemia
Authors: Shah Neil K. , Martin William L. , Whittle Martin J.
Published: January 2004

Objectives

Raised middle cerebral artery (MCA) Doppler velocity has been shown to be highly predictive of moderate to severe fetal anaemia. We present two false‐positive cases of raised MCA Doppler velocity in non‐immune hydropic fetuses.

Methods

In both cases, routine investigations for fetal hydrops, as well as detailed ultrasound scanning and MCA peak‐systolic velocity Doppler assessment (maximum velocity taken at zero degrees to the vessel), were performed. Fetal blood sampling was carried out at the same visit.

Results

MCA peak‐systolic velocity values greater than 1.50 MoM for gestation were found in both cases. However, both fetuses had normal haemoglobin values and haematocrits. Both fetuses died in utero soon after diagnosis.

Conclusions

A raised MCA velocity in a hydropic fetus may not always be due to fetal anaemia, rather it may indicate a fetus in poor condition perhaps due to cardiovascular decompensation and redistribution of blood to the fetal brain. Copyright © 2003 John Wiley & Sons, Ltd.
Prenatal diagnosis of premature centromere division–related mosaic variegated aneuploidy
Authors: Chen Chih‐Ping , Lee Chen‐Chi , Chen Wen‐Lin , Wang Wayseen , Tzen Chin‐Yuan
Published: January 2004

Objectives

To present the prenatal diagnosis of premature centromere division (PCD)‐related mosaic variegated aneuploidy (MVA) and a review of the literature.

Case and Methods

A 33‐year‐old primigravida woman underwent amniocentesis at 22 weeks' gestation because of intrauterine growth restriction (IUGR), microcephaly, and oligohydramnios. Amniocentesis revealed PCD‐related MVA. Repeat amniocentesis two weeks later consistently showed PCD‐related MVA. The pregnancy was terminated. The proband postnatally manifested dysmorphic facial features of microcephaly, hypertelorism, low‐set ears, a broad nasal bridge, a thin upper lip, and overriding toes. At autopsy, the internal organs were unremarkable. Cytogenetic analyses of the cord blood, liver, lungs, skin, and placenta displayed PCD‐related MVA in all tissues studied. The PCD frequencies for the cells in the amniotic fluid (first culture), amniotic fluid (second culture), cord blood, liver, lungs, skin, and placenta were 53.3%, 56.5%, 47.4%, 38.7%, 33.9%, 33.3%, and 40.8% respectively.

Conclusion

The present case provides evidence that, in cases of pregnancy with PCD‐related MVA, the cytogenetic result of the amniocytes correlates well with those of the fetal cells and chorionic villi cells. We suggest that prenatal sonographic detection of a complex of IUGR, microcephaly and oligohydramnios with or without central nervous system abnormalities should include a differential diagnosis of PCD‐related MVA. Copyright © 2003 John Wiley & Sons, Ltd.
Multi‐channel magnetocardiography for detecting beat morphology variations in fetal arrhythmias
Authors: Sturm R. , Müller H.‐P. , Pasquarelli A. , Demelis M. , Erné S. N. , Terinde R. , Lang D.
Published: January 2004

Objective

Over the last few years, a number of studies have shown that fetal magnetocardiography (fMCG) is useful in describing fetal cardiac activity. A 55‐channel MCG system in Ulm was used to record fetal cardiac activity in 12 pregnant women (with normal fetal heart activity in echocardiography) and in 5 pregnant women in whom the echocardiography showed fetal arrhythmias.

Method

The recorded MCG data were treated in order to eliminate the maternal signal and three MCG channels with the best signals were used to emulate a standard electrocardiogram (ECG) recording so that standard MCG analysis could be performed.

Results

The results in assessing fetal electrophysiology, demonstrating its potential, are presented here for two fetuses with recorded supraventricular extrasystoles (SVES) and for one with ventricular extrasystoles (VES). Concerning the SVES, the analysis software OMEGA was able to separate three different beat morphologies. The VES could be detected exactly and have been confirmed by postnatal ECG.

Conclusion

The beat morphology and the beat‐to‐beat variations allow new insights into the electrophysiology of the fetal heart. Copyright © 2003 John Wiley & Sons, Ltd.
The prenatal diagnosis of cloacal dysgenesis sequence in six cases: can the termination of pregnancy always be the first choice?
Authors: Sahinoglu Zeki , Mulayim Baris , Ozden Selcuk , Etker Seref , Celayir Aysenur , Ozkan Ferda , Bilgic Remziye
Published: January 2004

Objective

Cloacal dysgenesis sequence is a lethal malformation, which usually requires termination. In this study, our aim was to evaluate the prenatal and postnatal diagnostic features of cloacal dysgenesis sequence and review the management of the patients.

Material and Methods

The data of six cases of cloacal dysgenesis sequences were collected from the ultrasonography and neonatal records. The findings were evaluated in prenatal and postnatal periods. Chromosomal analysis was performed in all the cases. The evaluation of primary and secondary malformations was done. Coexisting anomalies were searched for by radiology and histopathology.

Results

Malformations in six cases (two females and four males) were described. The absence of anal, genital, and urinary openings with intact perineum covered by smooth skin were common findings. These features were considered as primary malformations for cloacal dysgenesis sequence. Secondary anomalies (urinary and gastrointestinal system malformations, pulmonary hypoplasia, and other coexisting anomalies) were evaluated.

Conclusion

The prenatal differential diagnosis of cloacal dysgenesis sequence from other urinary obstructive diseases was essential regarding fetal prognosis, prenatal, and neonatal management. The bladder outlet obstruction and pulmonary hypoplasia due to reduced amniotic fluid and/or kidney disease were considered prognostic factors for neonatal death. Termination of pregnancy is almost always recommended instead of intrauterine shunt procedures; but if we take into consideration one of our cases and a few reported cases who survived in the neonatal period, the prenatal management of these pregnancies needs to be reevaluated. Copyright © 2003 John Wiley & Sons, Ltd.
Second‐trimester diagnosis of intracranial vascular anomalies in a fetus with subdural hemorrhage
Authors: Strigini Francesca A. L. , Nardini Vincenzo , Carmignani Arianna , Valleriani Anna Maria
Published: January 2004

Objectives

Risk factors for intracranial hemorrhage occurring in prenatal life are imperfectly known. A case of prenatal diagnosis of subdural hemorrhage associated with multiple intracranial vascular aneurysms is described.

Methods

Sonography and magnetic resonance imaging of the fetal head were obtained at 21 weeks' gestation and compared with pathologic findings.

Results

Sonography showed a large transonic mass displacing the normal intracranial structures. Magnetic resonance imaging demonstrated the hemorrhagic origin of the mass and showed multiple vascular anomalies. Postmortem examination confirmed the compression of the cerebral hemisphere by a blood collection, probably because of bleeding from one of the multiple vascular aneurysms into the subdural space.

Conclusion

Magnetic resonance imaging with the use of single‐shot ultrafast sequences may be useful not only in the differential diagnosis of fetal intracranial hemorrhage but also in identifying vascular risk factors. Copyright © 2003 John Wiley & Sons, Ltd.
Follow‐up of children with isolated fetal echogenic bowel with particular reference to bowel‐related symptoms
Authors: Patel Y. , Boyd P. A. , Chamberlain P. , Lakhoo K.
Published: January 2004

Objectives

To determine whether there was any evidence of long‐term bowel pathology in children, apparently healthy at birth, who had a prenatal second‐trimester diagnosis of isolated grade 2 fetal echogenic bowel.

Methods

This was a retrospective study using data from the Oxford Congenital Anomaly Register. Fetuses with isolated grade 2 fetal echogenic bowel and date of delivery from 1994 to 2000 inclusive were identified. Information about the health of the children, particularly relating to bowel symptoms, was obtained from hospital records and from a questionnaire sent to the general practitioner.

Results

A total of 109 cases were identified, with delivery details available for 108. There was one unexplained intrauterine death, and additional problems were subsequently diagnosed in four cases (cystic fibrosis (2), Down syndrome (1), and VACTERL (1)). Questionnaires were sent to the GPs of the 103 who had no problems identified at the time of discharge from the maternity hospital. Age at follow‐up ranged from one to four years. Responses to the questionnaires were received from 83 (81%). Of these, 74 (89%) had not reported bowel symptoms to the GP, 9 (11%) reported symptoms relating to constipation (6), chronic abdominal pain (1), infantile colic with milk intolerance (1) and gastro‐oesophageal reflux (1).

Conclusion

This small study provides some reassurance that there was no evidence of any serious long‐term bowel pathology associated with isolated fetal echogenic bowel. Copyright © 2003 John Wiley & Sons, Ltd.
Clinical, cytogenetic, and molecular findings of prenatally diagnosed mosaic trisomy 4
Authors: Chen Chih‐Ping , Chern Schu‐Rern , Lee Chen‐Chi , Chang Tung‐Yao , Wang Wayseen , Tzen Chin‐Yuan
Published: January 2004

Objectives

To present the clinical, cytogenetic, and molecular findings of prenatally diagnosed mosaic trisomy 4.

Case

An amniocentesis was performed at 21 weeks' gestation because of maternal anxiety. Cytogenetic analysis revealed mosaicism for trisomy 4, 47,XX,+4[4]/46,XX[16]. Level II ultrasound demonstrated tetralogy of Fallot. Repeated amniocentesis at 23 weeks' gestation revealed 47,XX,+4[4]/46,XX[19]. The pregnancy was terminated. Phenotypic findings included tetralogy of Fallot, hypertelorism, micrognathia, abnormal ears, duplicated phalanges of the left thumb, clinodactyly, and overlapping of the toes. The karyotype of the cord blood was 46,XX. Cytogenetic analyses of the multiple tissue samplings showed a karyotype of 47,XX,+4 in 40/40 cells of the amniotic membrane (amnion), and 47,XX,+4/46,XX with various levels of trisomy 4 in the cells of the liver, lungs, placenta, skin, and umbilical cord. The levels of trisomy 4 were 11/40 in the liver, 8/40 in the lungs, 31/40 in the placenta, 9/40 in the skin, and 8/40 in the umbilical cord.

Method

The parental origin and meiotic origin of trisomy 4 were determined by examining the amniotic membrane using quantitative fluorescent polymerase chain reaction assays with polymorphic markers specific for chromosome 4. The result was consistent with a paternal meiosis I nondisjunction error. The cord blood showed a biparental inheritance. An extra paternal heterozygous allele with partial dosage increase was noted in other fetal and extraembryonic tissues studied.

Conclusion

A diagnosis of trisomy 4 mosaicism in amniocytes indicates an increased risk for fetal abnormalities. Associated abnormal findings include congenital heart defects and anomalies of the digits and thumb. A confirmatory placental sampling may be helpful, whereas a fetal blood sampling is of a very limited value. A postnatal amnion sampling may provide additional clues to the fetal involvement of trisomy 4. Copyright © 2004 John Wiley & Sons, Ltd.
Interleukin‐8 mRNA in vaginal secretions: a prenatal marker of congenital infection in case of preterm labor with intact membranes
Authors: Kayem G. , Maillard F. , Batteux F. , Weill B. , Cabrol D. , Goffinet F.
Published: January 2004

Objective

To study whether interleukin‐8 (IL‐8) mRNA in vaginal secretions is associated with congenital infection and preterm delivery in the case of preterm labor with intact membranes.

Methods

This prospective clinical study in a tertiary referral center included 280 patients who gave birth to 360 infants from 1997 through 1999. IL‐8 mRNA in vaginal secretions was determined with reverse transcriptase polymerase chain reaction. Logistic regression was used to examine the association between vaginal IL‐8 mRNA and congenital infection independently of the time of birth. Main outcome measures were congenital infection and delivery before 37 and 33 weeks' gestation.

Results

A total of 100 women (100/280 (35.7%)) gave birth before 37 weeks. A total of 54 children (54/360 (15%)) had congenital infection. IL‐8 mRNA in vaginal secretions was associated with delivery within 14 days of the sampling (24 (15.6%) vs. 7 (5.6%) p < 0.01), but not with delivery within 48 h, 7 days (p = 0.07) or before 37 or 33 weeks. There were more congenital infections in the group with detectable IL‐8 mRNA (37 (19.3%) than in the negative group (17 (10.1%); p < 0.05). IL‐8 mRNA was associated with congenital infection independently of the time of birth (OR: 2.6 (1.3–5.1)). This test had a sensitivity for predicting neonatal infection of 69%. Its specificity was 49%, its positive predictive value 19%, and its negative predictive value 90%.

Conclusion

IL‐8 mRNA could be a prenatal noninvasive vaginal marker of congenital infection. Copyright © 2004 John Wiley & Sons, Ltd.
Prenatal diagnosis of mosaic trisomy 16 associated with congenital diaphragmatic hernia and elevated maternal serum alpha‐fetoprotein and human chorionic gonadotrophin
Authors: Chen Chih‐Ping , Shih Jin‐Chung , Chern Schu‐Rern , Lee Chen‐Chi , Wang Wayseen
Published: January 2004

Objectives

To present the clinical, cytogenetic, and molecular findings of prenatally diagnosed mosaic trisomy 16.

Case

A 30‐year‐old gravida 2, para 1 woman was referred for amniocentesis because of a positive maternal serum screen result with elevated maternal serum alpha‐fetoprotein (MSAFP) and maternal serum free β‐human chorionic gonadotrophin (MSfreeβ‐hCG). Cytogenetic analysis of amniotic fluid at 21 weeks' gestation revealed mosaicism for trisomy 16, 47,XX,+16[3]/46,XX[15]. Ultrasonography demonstrated right diaphragmatic hernia and agenesis of left umbilical artery. The pregnancy was terminated subsequently. The karyotype of the cord blood was 46,XX. Cytogenetic analyses of the multiple sampled tissue specimens showed a karyotype of 47,XX,+16 in the placenta and 47,XX,+16/46,XX with various levels of trisomy 16 in the umbilical cord and skin. Molecular studies showed that the trisomy 16 in the placenta was likely to have resulted from a maternal meiosis II nondisjunction error. Partial dosage increase of an extra maternal allele was noted in the skin and umbilical cord.

Conclusion

Fetuses with mosaic trisomy 16 may be associated with congenital diaphragmatic hernia and elevated MSAFP and MShCG. Fetal blood sampling is of a limited value in confirming mosaic trisomy 16 ascertained through amniocentesis. Copyright © 2004 John Wiley & Sons, Ltd.
Interband transitions of wide‐band‐gap ternary pnictide BeCN2 in the chalcopyrite structure
Authors: Chiker F. , Abbar B. , Bouhafs B. , Ruterana P.
Published: January 2004

Equilibrium lattice constants, bulk modulus, electronic band structure, and different optical transitions calculated by means of the full potential linearized augmented plane wave method are presented for BeCN2 in the chalcopyrite structure. Analysis of the band structure suggests a pseudo‐direct band gap, which refers to an indirect band gap in binary compounds. We also discuss the relationships of the principal band gaps of the c‐BN zinc‐blende analogs. We investigate the assignment of the different optical transitions that are discussed in more detail from the reflectivity spectra. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of localized Mn spins in diluted‐magnetic‐semiconductor nanostructures with quantum dots
Authors: Scherbakov A. V. , Akimov A. V. , Yakovlev D. R. , Ossau W. , Molenkamp L. W. , Terai Y. , Kuroda S. , Takita K. , Souma I. , Oka Y.
Published: January 2004

Dynamics of spin–lattice relaxation of the magnetic Mn‐ion system is investigated for nanostructures with (Cd,Mn)Te and (Cd,Mn)Se diluted‐magnetic‐semiconductor (DMS) quantum dots. A nonequilibrium phonon technique with optical detection of the induced heating of the magnetic ion system was exploited. A strongly nonexponential decay of the spin dynamics is found to be specific for the DMS quantum dots. It is explained in the frame of a model suggesting that the spin dynamics in quantum dots is strongly affected by a spin diffusion into/from a DMS wetting layer, where the spin–lattice relaxation rate differs from that in the quantum dots. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new band in Cr3+‐doped MgAl2O4 natural spinel at room temperature
Authors: Phan The‐Long , Phan Manh‐Huong , Yu Seong‐Cho
Published: January 2004

Time resolved photoluminescence spectra of natural MgAl2O4 spinel doped with Cr3+ ions have been investigated at room temperature in the wavelength range between 380 and 800 nm. Using several excitation sources from the different lasers we have observed a new band, namely K, with a peak of 15,547 cm−1 (643.2 nm) and the transition process of photoluminescent lines among the electronic levels of the Cr3+ ion. In terms of the experimental results and the Tanabe‐Sugano diagram, we strongly propose that the K‐band originates from the electric dipole transition, 2Eg → 4A2g in the strong crystal field with Dq/B > 2.3. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A search for defect configurational changes in the post‐breakdown metastability of semi‐insulating GaAs
Authors: Luo Y. L. , Fung S. , Beling C. D. , Ling C. C. , Li S.
Published: January 2004

Recently room temperature electrically induced metastability in semi‐insulating (SI)‐GaAS has been reported in which the normally high resistivity state of SI‐GaAs converts into a low resistivity state when breakdown electric fields are applied to the metal/SI‐GaAs/metal systems. In this brief report, the methods of photo‐quenching and positron annihilation lifetime spectroscopy have been employed to see whether the high field breakdown and subsequent metastability has its origins in some configurational change of a native defect in the sample. Our results indicate that rather than being due to an atomic configurational change the observed metastability is most likely of purely electronic origin. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonequilibrium kinetics in spin‐crossover compounds
Authors: Gudyma Yu. , Semenko O.
Published: January 2004

We provide a detailed theoretical analysis of the non‐linear kinetics in spin‐crossover with the application of the nonequilibrium potential conception. The probability stationary density of a spin‐crossover system in the presence of a weak external noise of thermal origin and the mean first passage time of the potential barrier were obtained. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman scattering spectra of La3Ga5SiO14 (LGS) crystals
Authors: Lu G. W. , Li C. X. , Wang W. C. , Wang Z. H. , Wang Z. M. , Yuan D. R. , Xia H. R.
Published: January 2004

Based on the space group theory, the normal vibration modes of La3Ga5SiO14 (LGS) crystal were predicted, and the Raman scattering intensities of non‐polar and polar modes were calculated respectively. The lattice vibration and structure of LGS crystal were investigated by Raman spectroscopy and density‐functional theory (DFT). The DFT calculations were made on SiO4, GaO4, GaO6, La3Ga4O12 and La3Ga3SiO12 clusters, which model the atomic cluster in LGS crystal. Excellent agreement has been achieved between vibrational frequencies predicted by the theory and those observed in experiments. The layer structure of LGS crystal is identified, and its excellent piezoelectric properties are mainly attributed to the large polarizability anisotropy of La3Ga4O12 and La3Ga3SiO12 clusters, which results from the strong interaction between Ga(Si)O4 tetrahedras of LGS crystal. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ionic disorder and Yaffet–Kittel angle in nanoparticles of ZnFe2O4 prepared by sol‐gel method
Authors: Wang Li , Zhou Qingguo , Li Fashen
Published: January 2004

ZnFe2O4 nanoparticles have been prepared by sol‐gel methods. Mössbauer spectra from 4.2 K to RT showed their magnetic ordering took place at much higher temperature than that of bulk zinc ferrite. Mössbauer measurements that cover the temperature range 4.2 K to room temperature were acquired in zero field and an applied magnetic field of 5 T. The large increase of TN for nanoparticles can be attributed mainly to the redistribution of Fe and Zn cations on the A and B sites. Nanoparticles with smaller size have bigger θYK (Yaffet–Kittel angle). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mössbauer Study of ZnxCu1−xFe1.2Cr0.8O4
Authors: An D. H. , Kang K. U. , Lee B. G. , Lim J. B. , Jang S. U. , Baek K. S. , Choi E. J. , Oak H. N.
Published: January 2004

ZnxCu1−xFe1.2Cr0.8O4 (x = 0.0, 0.2, 0.4, 0.6) have been studied by Mössbauer spectroscopy, SQUID magnetometry, and X‐ray diffraction. The crystals are found to have a cubic spinel structure, and the lattice constant a0 increases linearly with increasing Zn concentration x. The iron ions are in ferric states and occupy both the tetrahedral (A) and octahedral (B) sites; the fraction of the iron irons at the A‐sites is 0.70 for x = 0 and decreases to 0.40 for x = 0.6. As the Zn concentration increases, both Néel temperature and magnetic hyperfine field decrease monotonically. While spin orderings are collinear for low Zn concentrations (x > 0.2), the spin canting emerges for x > 0.2 and increases with increasing Zn concentration; the canting angle at liquid helium temperature reaches up to 37° for x = 0.6. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic diffuse scattering of X‐rays in fcc 4He
Authors: Venkataraman C. T. , Schwoerer‐Böhning M. , Simmons R. O.
Published: January 2004

A first measurement of the dynamic diffuse scattering (DDS) of X‐rays was made in a fcc 4He crystal. The generally preferred method of studying lattice dynamics is through inelastic neutron scattering (INS). INS experiments, however, require large crystals which, in case of the high pressure fcc phase of helium are difficult to achieve and suffer from some poorly resolved phonon signals. An alternate promising technique uses a beryllium sample cell at cryogenic temperatures and excellent quality single crystals. Diffuse X‐ray scattering measurements on such fcc samples yield information about the elastic constants in solid 4He. Present test results on a crystal at 241(3) MPa and 23.8(1) K are compared with the results from neutron experiments and several theoretical calculations, including a present Hartree‐Fock LCAO model. Various disagreements are found and discussed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of low‐temperature magnetic relaxations in two systems GdAl2Dx (C15 Laves phase) and Fe3O4 (Inverse spinel)
Authors: Walz F. , Reule H. , Hirscher M. , Kronmüller H.
Published: January 2004

Most interestingly, the low‐temperature (T < 45 K) magnetic aftereffect (MAE) spectra occurring in both the cubic C15 Laves phase GdAl2Dx, after deuterium (D) charging, and in stoichiometric, singlecrystalline magnetite (Fe3O4) are of striking similarity – being composed of a plateau‐like relaxation zone (5 K < T < 30 K) and a pronounced Debye‐peak near T ≥ 30 K. Whereas the well‐investigated spectra in magnetite are well understood as resulting from various modes of thermally assisted incoherent tunneling of small polarons, not so much is known, as yet, concerning the respective mechanisms in GdAl2Dx. Guided by the impressive similarity of their spectra, we attempt here an interpretation of the underlying mechanisms in both systems on the basis of well‐corroborated magnetite concepts – i.e., in terms of incoherent tunnelling of specific particles, such as small polarons in Fe3O4 and deuterons in GdAl2Dx. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Symmetry aspects of exciton–exciton interactions and biexciton transitions in wurtzite semiconductor structures
Authors: Tronc P. , Kitaev Yu. E. , Smirnov V. P. , Jacobson M. , Neu G.
Published: January 2004

The inelastic collision of two excitons or the optical decay of a biexciton can induce a transition into an exciton and a photon. From the symmetry point of view, we have studied the states of free and bound biexcitons in bulk GaN with the wurtzite structure and in GaN/AlN heterostructures. Due to the antisymmetry properties arising from the exchange of identical fermions, the ground state of the free Γ biexcitons involving two holes from the same valence band is totally symmetric with respect to the symmetry group of the structure. We established the optical selection rules as well as the possible channels for the processes mentioned above and showed that, whatever is the symmetry of a biexciton, there are at least two channels for its optical recombination. That suggests fast recombination processes. If one (several) phonon(s) is (are) involved in a process, it is always possible to connect by an optical transition any initial state to any final one. An electric field applied parallel to the growth axis lowers the symmetry of superlattices to that of quantum wells. All the results remain valid for any bulk semiconductor with the wurtzite structure and for any wurtzite‐based heterostructure with identical cations or anions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some peculiar properties of the complex magnetic systems
Authors: Kapor D. , Pavkov M. , Manojlović M. , Pantić M. , Škrinjar M. , Stojanović S.
Published: January 2004

We treat two Heisenberg systems with complex magnetic structures: system with three sublattices and superlattice with three‐plane motive, with both ferromagnetic and antiferromagnetic coupling. Within Bloch's spin‐wave approximation they can be represented by a simple bosonic Hamiltonian with anomalous coupling. We show that the energies of the system can be derived by both Green function approach or so called “u–v” transformation. The basic result is that for a particular relation between sublattice spins i.e. S2 = S1 + S3 the system possess two acoustic (gapless) energy branches with linear dispersion law for small wave‐vectors. This leads to peculiar properties. In the Mean Field formalism, we show that the system in this case manifests so called weak ferromagnetism, and for certain system parameters, the three plane superlattice can posses one or even two compensation temperatures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the NQR detection of nitrogenated substances by multi‐pulse sequences
Authors: Mikhaltsevitch V. T. , Rudakov T. N.
Published: January 2004

Theoretical and practical aspects of using multi‐pulse spin‐locking and the “strong off‐resonant comb” (SORC) sequence for detecting nitrogenated substances by the nuclear quadrupole resonance method were studied. A number of optimum correlations between the parameters of multi‐pulse sequences and the relaxation characteristics of the substances under investigation were determined. The obtained relations were used for the fast detection of α‐trinitrotoluene (TNT). Relaxation parameters and temperature coefficients for twelve 14N lines of the orthorhombic phase of TNT measured at room temperature are also presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
kp‐approach for non‐symmetric short‐range defects: resonant states and alloy bandstructure
Authors: Vasko F. T.
Published: January 2004

The short‐range defect with reduced symmetry is studied in the framework of the kp‐approach taking into account a matrix structure of potential energy in the equations for envelope functions. The case of the narrow‐gap semiconductor, with defects which are non‐symmetric along the [001], [110], or [111] direction, is considered. A resonant state at a single defect is described within the Koster–Slater approximation. The bandstructure modification of the alloy, formed by non‐symmetric impurities, is discussed and a generalized virtual crystal approximation is introduced. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Model of a superconducting singular Fermi liquid with a first‐order phase transition
Authors: Gonczarek Ryszard , Krzyzosiak Mateusz
Published: January 2004

Model of s‐wave and d‐wave superconductivity in a singular Fermi liquid with a divergent scattering amplitude for particles with the same quasi‐momenta and opposite spins is formulated and presented with regard to a narrow, nearly half‐filled conduction band. The ground state and other eigenstates for the superconducting phase are found. Thermodynamic functions are obtained by the use of the Bogolubov method. The gap equation along with the equation for the chemical potential is derived in a general form and solved in a self‐consistent manner for s‐wave pairing. Above a certain temperature there are two solutions of the gap equation, however only for the greater one the superconducting phase remains stable. It is shown that the system undergoes a first‐order phase transition between the superconducting and the normal phase. The critical temperature and the heat of the transition are found. The temperature dependence of the entropy and the specific heat of the system is also presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two relaxation processes in the inhomogeneous deuterated ferroelectric Rb0.96(ND4)0.04D2AsO4
Authors: Trybuła Z. , Kaszyński J. , Łoś Sz. , Mielcarek S. , Trybuła M.
Published: January 2004

This paper reports the results of the influence of dc electric field on the complex permittivity ε* = ε′ – iε″ in the inhomogeneous deuterated ferroelectric Rb1−x(ND4)xD2AsO4, where x = 0.04 (DRADA with x = 0.04). In this crystal the coexistence of ferroelectric and short‐range ordered (glass) phases takes place at a low temperature below Tc. At Tc = 155 K the transition to the ferroelectric state is reported. Two relaxation processes were observed in the perpendicular orientation to the ferroelectric c‐axis in the temperature range from 3.5 K to 300 K. The influence of a dc electric field on the temperature dependence of the dielectric losses shows clearly two different relaxation processes. At temperatures around 60 K, there is a dispersion related to the embryos of the glass clusters, which coexists with ferroelectric domains. The dispersion around 120 K due to frozen domain wall motion is also observed in the perpendicular direction to the ferroelectric c‐axis along hydrogen bonds. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Molecular‐dynamics simulations of surface and bulk properties of Zn, Cd, and ZnCd systems
Authors: Amirouche Lynda , Erkoç Şakir
Published: January 2004

Surface and bulk properties of Zn, Cd, and ZnCd systems have been investigated by performing molecular‐dynamics simulations using a recently developed empirical many‐body potential energy function for these systems, which comprices two‐ and three‐body atomic interactions. Surface reconstruction and multilayer relaxation on clean surfaces, adatom on surface, substitutional atom on surface and bulk materials, and vacancy on surface and bulk materials have been studied extensively. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Band structure of a harmonically confined electron with an impenetrable boundary
Authors: Hai W. , Fang X. , Li F.
Published: January 2004

We study finite‐size effects of the spatially bounded quantum systems exemplified by a single‐electron quantum dot with a harmonic potential and an impenetrable boundary. A general solution of the corresponding Schrödinger equation is obtained and the unique special solution for any energy is derived from the normalization and boundary conditions. The classical‐mechanically allowable eigenenergies form the continuous spectrum or piecewise continuous bands with the minimum value being much less than the zero point energy of a free harmonic oscillator. As the increase of the confining size, the band widths reduce and the energies finally close to the discrete level of the free oscillator. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Field‐induced magnetic reorientation of the 2D Heisenberg ferromagnet with S = 1: the influence of an exchange anisotropy
Authors: Ilkovič V.
Published: January 2004

The two‐dimensional (2D) Heisenberg model with spin S = 1, with the exchange anisotropy plus a second‐order uniaxial single‐site anisotropy and an external transverse magnetic field is treated by the Tyablikov (Random Phase Approximation: RPA) decoupling of the exchange interaction term and the Anderson‐Callen decoupling of the anisotropy term. The orientation of the magnetization is determined by the expectation values 〈Sα〉 (α = x, z) of the spin components from which the orientation angle θ is obtained as a function of the temperature and of the transverse magnetic field for various parameters of the exchange anisotropy in the (x,y)‐plane. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin dependent distribution and Fermi surface of the perovskite manganite compound La0.7Sr0.3MnO3 via 2D‐ACAR measurements
Authors: Hamid A. S. , Arima T.
Published: January 2004

Using 2D angular correlation of positron annihilation radiation (ACAR) experiment, we have performed a systematic study of the spin dependent and Fermi surface of the colossal magneto‐resistance CMR La0.7Sr0.3MnO3. The measurements have been carried out using a re‐versal magnetic field direction (parallel and anti‐parallel to the direction of motion of the polarized posi‐trons). The measured spectra have been investigated in the momentum space as well as in the wave vector space. They revealed information about the hybridization effect of Mn(3d eg1) and O(2p) like states. Further, the results showed that the majority spin electrons predominated at the Fermi level. From another perspective, the Fermi surface of La0.7Sr0.3MnO3 revealed a cuboids hole surface centered on R point and a spheroid electron surface centered on Γ point. A comparison with the earlier results showed qualitative agreement. However, the current results could reveal the dimension of the electron surface centered on Γ point that was predicted in the earlier 2D‐ACAR measurements. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bound exciton and donor–acceptor pair recombinations in ZnO
Authors: Meyer B. K. , Alves H. , Hofmann D. M. , Kriegseis W. , Forster D. , Bertram F. , Christen J. , Hoffmann A. , Straßburg M. , Dworzak M. , Haboeck U. , Rodina A. V.
Published: January 2004

The optical properties of excitonic recombinations in bulk, n‐type ZnO are investigated by photoluminescence (PL) and spatially resolved cathodoluminescence (CL) measurements. At liquid helium temperature in undoped crystals the neutral donor bound excitons dominate in the PL spectrum. Two electron satellite transitions (TES) of the donor bound excitons allow to determine the donor binding energies ranging from 46 to 73 meV. These results are in line with the temperature dependent Hall effect measurements. In the as‐grown crystals a shallow donor with an activation energy of 30 meV controls the conductivity. Annealing annihilates this shallow donor which has a bound exciton recombination at 3.3628 eV. Correlated by magnetic resonance experiments we attribute this particular donor to hydrogen. The Al, Ga and In donor bound exciton recombinations are identified based on doping and diffusion experiments and using secondary ion mass spectroscopy. We give a special focus on the recombination around 3.333 eV, i.e. about 50 meV below the free exciton transition. From temperature dependent measurements one obtains a small thermal activation energy for the quenching of the luminescence of 10 ± 2 meV despite the large localization energy of 50 meV. Spatially resolved CL measurements show that the 3.333 eV lines are particularly strong at crystal irregularities and occur only at certain spots hence are not homogeneously distributed within the crystal contrary to the bound exciton recombinations. We attribute them to excitons bound to structural defects (Y‐line defect) very common in II–VI semiconductors. For the bound exciton lines which seem to be correlated with Li and Na doping we offer a different interpretation. Li and Na do not introduce any shallow acceptor level in ZnO which otherwise should show up in donor–acceptor pair recombinations. Nitrogen creates a shallow acceptor level in ZnO. Donor–acceptor pair recombination with the 165 meV deep N‐acceptor is found in nitrogen doped and implanted ZnO samples, respectively. In the best undoped samples excited rotational states of the donor bound excitons can be seen in low temperature PL measurements. At higher temperatures we also see the appearance of the excitons bound to the B‐valence band, which are approximately 4.7 meV higher in energy. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Feature Article: Bound exciton and donor–acceptor pair recombinations in ZnO
Authors: Meyer B. K. , Alves H. , Hofmann D. M. , Kriegseis W. , Forster D. , Bertram F. , Christen J. , Hoffmann A. , Straßburg M. , Dworzak M. , Haboeck U. , Rodina A. V.
Published: January 2004

The article [1] features the current state of knowledge on the optical properties of excitonic and donor–acceptor pair recombination in bulk n‐ZnO, as revealed by recent photo‐ and cathodoluminescence measurements.

The cover picture is a photograph showing an unusual look at the green luminescence of rod‐shaped ZnO crystals under ultraviolet excitation.

The first author, Bruno K. Meyer, is professor of physics at the Justus Liebig University of Giessen. His scientific interests include synthesis of semiconductor oxides by chemical vapour deposition and magnetron sputtering, in particular with respect to doping issues, materials science of electro‐ and thermochromic materials, recombination phenomena and defect characterization by magnetic resonance.

This issue also contains an Editor's Choice on “Evolution of molecular ordering and phase transitions in C60/C70 solid solutions” by Gabriela Rueda‐Morales and Jaime Ortiz‐López [2].
Effect of equity ownership on the survival of international joint ventures
Authors: Dhanaraj Charles , Beamish Paul W.
Published: January 2004

This note extends transaction cost analysis of international joint ventures (IJVs) to include explicitly the effect of equity. It challenges the common practice of treating all foreign investments with between 5 percent and 95 percent equity as IJVs. A fine‐grained analysis of the role of foreign equity ownership on the survival of 12,984 overseas subsidiaries confirms a declining, nonlinear, and asymmetrical relationship between equity and mortality in overseas subsidiaries. While investments involving small ownership levels (<20%) have very high mortality rates, those with high ownership levels (>80%) have mortality rates comparable to that of wholly owned subsidiaries. Implications for research, practice, and policy are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Strategic benefits to firms issuing private equity placements
Authors: Folta Timothy B. , Janney Jay. J.
Published: January 2004

For young technology firms, acquiring resources can often be costly due to the information asymmetry and uncertainty that exist surrounding the new technology. We contend that firms able to issue private equity can better manage their ability to mobilize three kinds of resources: capital, research partners, and commercial partners. We investigate the existence of long‐term, strategic benefits to private placements, and a number of factors may determine the long‐term effectiveness of this governance form. Overall, the empirical analyses demonstrates that private placements provide long‐term benefits to firms by reducing hazards associated with information asymmetry. Copyright © 2003 John Wiley & Sons, Ltd.
An empirical test of heuristics and biases affecting real option valuation
Authors: Miller Kent D. , Shapira Zur
Published: January 2004

This study applies insights from behavioral decision theory to explain how managers value call and put options. Behavioral decision theory points to important deviations from the assumptions of normative option pricing models in finance. We used a questionnaire to collect option pricing data to test our behavioral hypotheses. The evidence indicates specific biases affecting subjective valuations of options: (1) buyers and sellers price options below their expected values; (2) buyers' prices are consistently below sellers' prices; (3) irrelevant outcomes decrease option values; (4) discount rates vary with the option time horizon; and (5) changes in option values do not fully reflect increases in exercise prices. We discuss the implications of these findings for the management of real options and suggest directions for developing descriptive real option theory. Copyright © 2003 John Wiley & Sons, Ltd.
Explaining outcomes in competition among foreign multinationals in a focal host market
Authors: Rangan Subramanian , Drummond Aldemir
Published: January 2004

Multinational enterprises (MNEs) from different home regions now routinely confront one another in third markets. There is, however, little conceptual or theoretical literature on the determinants of outcome patterns in these contests. This paper offers a first attempt at systematic and parsimonious conceptualization of the issue. In Brazil, for instance, while U.S.‐based MNEs such as Coca‐Cola and IBM lead in their sectors, other leading U.S. MNEs including Citibank, GE, and Pfizer are outsold by European rivals that appear less competitive globally. Extending theory on the liability of foreignness and firm‐specific advantages, we contend that (i) the MNE whose home nation has greater ties to the focal host nation (along geographic, colonial, immigration, linguistic, and institutional dimensions) will lead in that host nation; and (ii) ties notwithstanding, if an MNE's firm‐specific advantages are so superior that it outsells a rival MNE in that rival's home market, then it will outsell that rival as well in the focal host market. Based on this we develop a conceptual framework, statistical analysis pertaining to MNE competition in Brazil, and three avenues for fruitful new research. Copyright © 2003 John Wiley & Sons, Ltd.
Exploration and exploitation alliances in biotechnology: a system of new product development
Authors: Rothaermel Frank T. , Deeds David L.
Published: January 2004

We link the exploration–exploitation framework of organizational learning to a technology venture's strategic alliances and argue that the causal relationship between the venture's alliances and its new product development depends on the type of the alliance. In particular, we propose a product development path beginning with exploration alliances predicting products in development, which in turn predict exploitation alliances, and that concludes with exploitation alliances leading to products on the market. Moreover, we argue that this integrated product development path is moderated negatively by firm size. As a technology venture grows, it tends to withdraw from this product development path to discover, develop, and commercialize promising projects through vertical integration. We test our model on a sample of 325 biotechnology firms that entered 2565 alliances over a 25‐year period. We find broad support for the hypothesized product development system and the moderating effect of firm size. Copyright © 2004 John Wiley & Sons, Ltd.