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1.
Childs Nerv Syst ; 40(3): 647-653, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37857860

RESUMO

PURPOSE: The utility and safety of including two neurosurgeons for tumor resections is unknown. This study compares outcomes among pediatric patients with craniopharyngiomas operated on with a dual or single surgeon approach (DSA, SSA). METHODS: A single-center review identified all craniopharyngioma transsphenoidal or craniotomy resections from 2000 to 2020. Surgical years of experience (YOE) and rates of 5-year reoperations, complications, recurrence, and postoperative radiotherapy were analyzed. RESULTS: Twenty-six transsphenoidal and 68 craniotomies were identified among 62 patients. Eleven transsphenoidal (42.3%) utilized DSA and 15 utilized (57.7%) SSA. Eight craniotomies (11.8%) were DSA and 60 (88.2%) were SSA. The surgeon for SSA transsphenoidal procedures had a median of 10.7 YOE (IQR: 9.9-13.7) versus 6.6 (IQR: 2.7-16; p = 0.058) for the lead surgeon in DSAs. The co-surgeon in transsphenoidal DSAs had a median of 27 YOE (IQR: 11.8-35.7). The surgeon for SSA craniotomies had a median of 19.3 YOE (IQR: 12.1-26.4) versus 4.5 years (IQR: 1.3-15.3; p = 0.017) for the lead surgeon in DSA cases. The co-surgeon in DSA craniotomies had a median of 23.2 YOE (IQR: 12.6-31.4). Case complexity was similar across transsphenoidal groups. DSA transsphenoidal resections had fewer complications (18% DSA vs. 33% SSA), reoperations (45% vs. 53%), and radiation therapy (9.1% DSA vs. 33% SSA) than SSA. CONCLUSION: Lead surgeons in DSAs are frequently junior surgeons while SSAs typically employ senior surgeons. Outcomes did not significantly differ between DSA and SSA. Mentorship through DSAs does not negatively affect patient care.


Assuntos
Craniofaringioma , Neoplasias Hipofisárias , Humanos , Criança , Craniofaringioma/radioterapia , Craniofaringioma/cirurgia , Craniofaringioma/complicações , Neurocirurgiões , Resultado do Tratamento , Estudos Retrospectivos , Neoplasias Hipofisárias/radioterapia , Neoplasias Hipofisárias/cirurgia , Neoplasias Hipofisárias/complicações , Complicações Pós-Operatórias/etiologia
2.
J Craniofac Surg ; 32(8): e737-e739, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34172679

RESUMO

ABSTRACT: A 3-month-old patient presented for evaluation by plastic surgery with marked trigonocephaly and was subsequently diagnosed with metopic craniosynostosis. During presurgical evaluation, the patient was found to have two variants of the NOTCH3 gene, resulting in the diagnosis of lateral meningocele (Lehman) syndrome. Due to the increased possibility of stroke associated with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, the patient underwent only anterior calvarial vault remodeling without fronto-orbital advancement for correction of her craniosynostosis. This unique constellation of symptoms, and its impact on operative management, has not been previously described in the literature.


Assuntos
CADASIL , Craniossinostoses , Anormalidades Múltiplas , Craniossinostoses/diagnóstico por imagem , Craniossinostoses/genética , Craniossinostoses/cirurgia , Feminino , Humanos , Lactente , Meningocele , Mutação , Receptor Notch3/genética
3.
J Pediatr ; 216: 142-149.e2, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31685225

RESUMO

OBJECTIVE: To evaluate patient outcomes of minimally invasive endoscopic strip craniectomy (ESC) for craniosynostosis. STUDY DESIGN: This is a retrospective cohort analysis (2004-2018) of 500 consecutive infants with craniosynostosis treated by ESC with orthotic therapy at a single center. Operative outcomes included transfusions, complications, and reoperations as well as head circumference change based on World Health Organization percentiles. Multivariable logistic regression was used to identify risk factors associated with blood transfusion. Paired t tests were used for within-patient comparisons and Fisher exact test to compare syndromic and nonsyndromic subgroups. RESULTS: ESC was associated with low rates of blood transfusion (6.6%), complications (1.4%), and reoperations (3.0%). Risk factors for transfusion included syndromic craniosynostosis (P = .01) and multiple fused sutures (P = .02). Median surgical time was 47 minutes, and hospital length of stay 1 day. Transfusion and reoperation rates were higher among syndromic patients (both P < .001). Head circumference normalized by 12 months of age relative to World Health Organization criteria in infants with sagittal, coronal, and multisuture craniosynostosis (all P < .001). CONCLUSIONS: ESC is a safe, effective, and durable correction of infantile craniosynostosis. ESC can achieve head growth normalization with low risks of blood transfusion, complications, or reoperation. Early identification of craniosynostosis in the newborn period and prompt referral by pediatricians allows families the option of ESC vs larger and riskier open reconstruction procedures.


Assuntos
Craniossinostoses/cirurgia , Craniotomia/métodos , Endoscopia , Estudos de Coortes , Feminino , Humanos , Lactente , Estudos Longitudinais , Masculino , Estudos Retrospectivos , Resultado do Tratamento
4.
Childs Nerv Syst ; 36(12): 3007-3012, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32363544

RESUMO

OBJECTIVES: To recognize the national trends in management of pediatric craniopharyngioma and to address the significant predictors of discharge disposition. METHODS: We utilized the Kids' Inpatient Database (KID), a pediatric inpatient sample generated by the Healthcare Cost and Utilization Project (HCUP) triennially from 1997 to 2016. RESULTS: KID contains 2141 pediatric craniopharyngioma admissions. Patient demographics had no effect on discharge disposition. Based on the multivariable logistic regression analysis, we confirmed a significantly higher non-routine discharge rate among patients with hydrocephalus (P = 0.01). Patients who developed diabetes insipidus were at higher risk for non-routine discharge (P = 0.02). Admission of patients to a freestanding children's hospital increased the likelihood of routine discharge (P = 0.001). CONCLUSION: Hydrocephalus, diabetes insipidus, and admission to a freestanding children's hospital are significant independent predictors of discharge disposition.


Assuntos
Craniofaringioma , Neoplasias Hipofisárias , Criança , Craniofaringioma/epidemiologia , Bases de Dados Factuais , Hospitalização , Humanos , Pacientes Internados , Tempo de Internação , Alta do Paciente , Estados Unidos/epidemiologia
5.
Med Vet Entomol ; 28(3): 264-72, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24797405

RESUMO

Despite decades of research, there is still no agreement on which indices of Aedes aegypti (Stegomyia aegypti) (Diptera: Culicidae) presence and abundance better quantify entomological risk for dengue. This study reports the results of a multi-scale, cross-sectional entomological survey carried out in 1160 households in the city of Merida, Mexico to establish: (a) the correlation between levels of Ae. aegypti presence and abundance detected with aspirators and ovitraps; (b) which immature and egg indices correlate with the presence and abundance of Ae. aegypti females, and (c) the correlations amongst traditional Aedes indices and their modifications for pupae at the household level and within medium-sized geographic areas used for vector surveillance. Our analyses show that ovitrap positivity was significantly associated with indoor adult Ae. aegypti presence [odds ratio (OR) = 1.50; P = 0.03], that the presence of pupae is associated with adult presence at the household level (OR = 2.27; P = 0.001), that classic Aedes indices are informative only when they account for pupae, and that window screens provide a significant level of protection against peridomestic Ae. aegypti (OR = 0.59; P = 0.02). Results reinforce the potential of using both positive collections in outdoor ovitraps and the presence of pupae as sensitive indicators of indoor adult female presence.


Assuntos
Aedes/fisiologia , Monitoramento Ambiental , Insetos Vetores/fisiologia , Aedes/crescimento & desenvolvimento , Animais , Estudos Transversais , Dengue/epidemiologia , Dengue/parasitologia , Feminino , Insetos Vetores/crescimento & desenvolvimento , Larva/fisiologia , México , Controle de Mosquitos , Óvulo/fisiologia , Densidade Demográfica , Pupa/fisiologia
6.
Radiography (Lond) ; 30(2): 517-523, 2024 03.
Artigo em Inglês | MEDLINE | ID: mdl-38245920

RESUMO

INTRODUCTION: Practice learning is critical to the development of clinical skills; hence placements are a major component of all pre-registration radiography programmes. Nonetheless, dissatisfaction with practicum experiences is a common reason why students consider leaving such programmes. Providing effective placements which promote retention may not only require better appreciation of students' clinical reflections, but also a more fundamental understanding of the implicit criteria they use to appraise a practicum. This study applied the theory of human relatedness (THR) to the placement experiences of radiography undergraduates to identify the evaluative mechanisms which may underpin these experiences. METHODS: A critical realist investigative approach was employed to reanalyse data regarding the practicum experiences of stakeholders involved in undergraduate diagnostic radiography programmes at two universities in Australia and Ethiopia against the eight core THR concepts, namely connectedness, disconnectedness, parallelism, enmeshment, belonging, reciprocity, mutuality, and synchrony. RESULTS: The findings identified all states of relatedness and processes/social competencies of the THR within the placement experiences of these stakeholders. The degree of positive relatedness a radiography student experiences within a practicum, irrespective of the setting, may affect their clinical performance. CONCLUSION: The findings support the argument that the THR may reflect an implicit set of criteria stakeholders use to evaluate clinical encounters. Additionally, these results are congruent with earlier investigations regarding the practicum reflections of other undergraduate healthcare students. IMPLICATIONS FOR PRACTICE: To enhance student placement experiences, it is necessary to recognise the effect a student's sense of relatedness may have on their self-efficacy and proficiency, modifying pre-practicum preparation and assessment arrangements to inhibit disconnectedness and enmeshment, avoid the need for parallelism, and better cultivate connectedness, belonging, reciprocity, mutuality, and synchrony.


Assuntos
Competência Clínica , Estudantes , Humanos , Etiópia , Austrália , Radiografia
7.
Cureus ; 16(4): e57931, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38738035

RESUMO

Left-handed surgical trainees are uniquely challenged when learning how to suture using standard needle drivers designed for right-handed individuals and often feel disadvantaged in comparison to their right-handed peers. "Palming," a suturing technique that improves suturing mechanics and efficiency, cannot be achieved in the standard manner using the left hand. This paper proposes a previously undescribed technique for palming using the left hand that provides many of the same benefits as standard palming methods using the right hand, potentially reducing a common source of inequity in surgical training.

8.
Neurosurgery ; 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38856202

RESUMO

BACKGROUND AND IMPORTANCE: Trephination is a procedure in which a small hole is made in the skull. Rare cases of self-trephination by individuals seeking medical benefit have been reported. Excoriation disorder is a compulsive skin-picking condition in which an individual self-inflicts cutaneous lesions. Left untreated, severe excoriation disorder can pose significant health risks. CLINICAL PRESENTATION: Here, we describe 5 patients who presented with self-trephination due to a severe form of compulsive cranial excoriation at 2 neighboring academic medical centers over a 4-year period. We review the clinical presentation of self-trephination in cranial excoriation disorder and associated risk factors, surgical and nonsurgical interventions, complications of the disease, treatments, and mortality. Defining clinical characteristics include repetitive self-induced destruction of the scalp and skull with entry into the intracranial compartment, frequent psychiatric comorbidities, infection or injury of the brain with consequent neurological morbidity or mortality, and frequent treatment failures because of poor adherence. CONCLUSION: Self-trephination in cranial excoriation disorder is a severe neuropsychological disorder and neurosurgical emergency that exposes the brain and is often life-threatening. Appropriate therapy requires antibiotics, surgical debridement and repair of the wound, and concomitant effective psychiatric management of the underlying compulsion, including the use of antidepressants and behavioral therapy.

9.
Phys Rev Lett ; 110(13): 136401, 2013 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-23581347

RESUMO

Electron capture during forward bias and reemission at zero bias by divacancies in the depletion region of a silicon diode structure at room temperature have been studied for the first time using monoenergetic positrons. The positron response increases essentially linearly with electron current, as a result of increased positron trapping by negatively charged divacancies. The measurements indicate that ≤1% of the divacancies become negatively charged in the steady state at a forward bias of 1 V. Changes in the mean positron response when applying a square wave bias to the sample (1 V forward bias and 0 V, duty cycle 1:4, times at 0 V in the range 0.1-100 µs), were consistent with a rapid conversion of doubly to singly charged divacancies (in ∼10(1) ns), followed by slower defilling of the singly charged divacancies with a time constant of ∼10(1) µs. These ac measurements allow determination of the relative populations of singly and doubly charged divacancies. The results provide confirmation of consistency between the positron's response to the silicon divacancy and previously extracted capture and emission kinetics determined through charge transient measurements and assigned to the same defect. The possibility of combining these two, orthogonal techniques suggest a promising new and powerful approach to defect spectroscopy in which the structure and electrical properties of a defect may be determined in a single measurement.

10.
J Drugs Dermatol ; 12(6): 679-84, 2013 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-23839186

RESUMO

BACKGROUND: Intravenous immunoglobulin (IVIG) can be used to treat potentially deadly toxic epidermal necrolysis (TEN), milder Stevens Johnson Syndrome (SJS) and intermediate TEN/SJS overlap. Some formularies now deny IVIG for TEN based on the EuroSCAR TEN/SJS study that reported a nonsignificant trend toward increased mortality in 75 IVIG-treated TEN/SJS patients; of note the IVIG patients had more TEN and less SJS than patients in other treatment arms. EuroSCAR data on mortality among the 25 IVIG-treated TEN patients, use of nonsucrose IVIG, and admission to specialized settings such as burn units was not disclosed. The impact of treatment setting (specialized unit vs general ward) on IVIG efficacy has not previously been studied. OBJECTIVE: To evaluate efficacy of treating TEN with early nonsucrose IVIG in a burn unit. METHODS: Data were retrospectively collected from 13 IVIG-treated TEN patients admitted to a burn unit over a 6-year period. RESULTS: We report 0% mortality among 13 IVIG-treated TEN patients. Mortality was significantly lower than predicted by SCORTEN. Mortality was also significantly lower than the EuroSCAR groups receiving IVIG (P<.005), supportive care (P<.018), and corticosteroids only (P<.046). CONCLUSION: TEN patients may benefit from early nonsucrose IVIG administered in burn units or other specialized settings.


Assuntos
Imunoglobulinas Intravenosas/uso terapêutico , Fatores Imunológicos/uso terapêutico , Síndrome de Stevens-Johnson/tratamento farmacológico , Adolescente , Adulto , Idoso , Unidades de Queimados , Criança , Feminino , Humanos , Imunoglobulinas Intravenosas/administração & dosagem , Imunoglobulinas Intravenosas/química , Fatores Imunológicos/administração & dosagem , Fatores Imunológicos/química , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Síndrome de Stevens-Johnson/mortalidade , Síndrome de Stevens-Johnson/fisiopatologia , Fatores de Tempo , Resultado do Tratamento , Adulto Jovem
11.
Proc Nutr Soc ; : 1-9, 2023 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-37759428

RESUMO

Consumption of snacks and ultra-processed foods (UPF) high in fat, salt and sugar (HFSS) is associated with rising rates of obesity and growing socioeconomic disparities in nutrition. While infancy, childhood and adolescence are critical periods for development of dietary preferences, there remains a dearth of research exploring factors that underpin snacking behaviour over this time. This review aims to address this gap by drawing from qualitative lived experience research, with 122 families of different socioeconomic position (SEP), to explore how the (i) home food environment, (ii) food environment and (iii) social value and meanings of food shape parental provision of snacks. This review shows that snacking holds important meanings in everyday family life, with infants integrated into existing snacking practices from an early age. Price promotions, low-cost and long shelf-lives all make UPF and HFSS snacks an appealing option for many low-SEP parents; while children's requests and preferences for HFSS snacks present a challenge across SEP. However, higher-SEP parents can ensure fresh fruits are always available as an alternative snack, while fruit is described as a financially risky expenditure for low-SEP families. The present findings also indicate that retailers and producers are increasingly promoting 'healthier' snacks through product packaging and marketing, such as 'meets one of your five a day', despite these products displaying similar nutritional profiles to traditional UPF and HFSS snacks. We outline a series of policy recommendations, including extending Healthy Start Vouchers and the Fruit and Vegetable Scheme in schools and action to address misleading product marketing and packaging.

12.
J Neurosurg Pediatr ; 32(2): 201-213, 2023 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-37178026

RESUMO

OBJECTIVE: Endoscopic third ventriculostomy (ETV) with choroid plexus cauterization (CPC) can avoid ventriculoperitoneal shunt (VPS) dependence in very young hydrocephalic children, although long-term success as a primary treatment in North America has not been previously reported. Moreover, optimal age at surgery, impact of preoperative ventriculomegaly, and relationship to prior cerebrospinal fluid (CSF) diversion remain poorly defined. The authors compared ETV/CPC and VPS placement for averting reoperation, and they evaluated preoperative predictors for reoperation and shunt placement after ETV/CPC. METHODS: All patients under 12 months of age who underwent initial hydrocephalus treatment via ETV/CPC or VPS placement at Boston Children's Hospital between December 2008 and August 2021 were reviewed. Analyses included Cox regression for independent outcome predictors, and both Kaplan-Meier and log-rank rank tests for time-to-event outcomes. Cutoff values for age and preoperative frontal and occipital horn ratio (FOHR) were determined with receiver operating characteristic curve analysis and Youden's J index. RESULTS: In total, 348 children (150 females) were included with principal etiologies of posthemorrhagic hydrocephalus (26.7%), myelomeningocele (20.1%), and aqueduct stenosis (17.0%). Of these, 266 (76.4%) underwent ETV/CPC and 82 (23.6%) underwent VPS placement. Treatment choice largely reflected surgeon preferences before practice shifted toward endoscopy, with endoscopy not considered for > 70% of initial VPS cases. ETV/CPC patients trended toward fewer reoperations, and Kaplan-Meier analysis estimated that 59% of patients would achieve long-term shunt freedom through 11 years (median 42 months of actual follow-up). Among all patients, corrected age < 2.5 months (p < 0.001), prior temporizing CSF diversion (p = 0.003), and excess intraoperative bleeding (p < 0.001) independently predicted reoperation. Among ETV/CPC patients, corrected age < 2.5 months (p = 0.031), prior CSF diversion (p = 0.001), preoperative FOHR > 0.613 (p = 0.011), and excessive intraoperative bleeding (p = 0.001) independently predicted ultimate conversion to VPS. The actual VPS insertion rates remained low in patients who were ≥ 2.5 months old at ETV/CPC either with prior CSF diversion (2/10 [20.0%]) or without prior CSF diversion (24/123 [19.5%]); however, the actual VPS insertion rates increased in patients who were < 2.5 months old at ETV/CPC with prior CSF diversion (19/26 [73.1%]) or without prior CSF diversion (44/107 [41.1%]). CONCLUSIONS: ETV/CPC successfully treated hydrocephalus in most patients younger than 1 year irrespective of etiology, averting observed shunt dependence in 80% of patients ≥ 2.5 months of age regardless of prior CSF diversion and in 59% of those < 2.5 months of age without prior CSF diversion. For infants aged < 2.5 months with prior CSF diversion, particularly those with severe ventriculomegaly, ETV/CPC was unlikely to succeed unless safely delayed.


Assuntos
Hidrocefalia , Neuroendoscopia , Terceiro Ventrículo , Criança , Feminino , Humanos , Lactente , Ventriculostomia/efeitos adversos , Resultado do Tratamento , Plexo Corióideo/cirurgia , Terceiro Ventrículo/cirurgia , Estudos Retrospectivos , Neuroendoscopia/efeitos adversos , Cauterização/efeitos adversos , Hidrocefalia/etiologia , Hidrocefalia/cirurgia
13.
J Neurosurg Pediatr ; : 1-7, 2023 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-36933265

RESUMO

OBJECTIVE: Morning glory disc anomaly (MGDA), a congenital abnormality of the optic nerve, may be associated with moyamoya arteriopathy, a cerebrovascular abnormality. In this study, the authors aimed to define the temporal evolution of cerebrovascular arteriopathy in patients with MGDA to characterize a rational strategy for screening and management over time. METHODS: The records of pediatric neurosurgical patients at two academic institutions were retrospectively reviewed to identify cases of cerebral arteriopathy and MGDA, including radiographic and clinical records documenting patient outcomes of medical and surgical management. RESULTS: Thirteen cases of moyamoya syndrome (MMS) associated with MGDA were identified in 13 children aged 0.6-17 years. The pattern of arteriopathy resembled that of non-MGDA MMS, with predominantly anterior circulation involvement. The arteriopathy lateralized with the MGDA, although 3 patients also had contralateral involvement. The overall group was followed for a median of 3.2 years. Radiological biomarkers of cerebral ischemia were applied to guide surgical decisions, and more than half of the patients (7 of 13) had evidence of stroke or progression on serial imaging. Nine patients underwent revascularization surgery, and 4 were managed medically. CONCLUSIONS: Cerebral arteriopathy observed in association with MGDA resembles MMS seen in patients without MGDA and is dynamic, with progression observed over months to years and an associated risk of cerebral ischemia that indicates a role for surgical revascularization. Radiological biomarkers may augment clinical data to identify candidates for revascularization surgery.

14.
Proc Natl Acad Sci U S A ; 106(37): 15573-6, 2009 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-19717461

RESUMO

The study of abrupt increases in magnetization with magnetic field known as metamagnetic transitions has opened a rich vein of new physics in itinerant electron systems, including the discovery of quantum critical end points with a marked propensity to develop new kinds of order. However, the electric analogue of the metamagnetic critical end point, a "metaelectric" critical end point, has been rarely studied. Multiferroic materials wherein magnetism and ferroelectricity are cross-coupled are ideal candidates for the exploration of this novel possibility using magnetic-field (H) as a tuning parameter. Herein, we report the discovery of a magnetic-field-induced metaelectric transition in multiferroic BiMn(2)O(5), in which the electric polarization (P) switches polarity along with a concomitant Mn spin-flop transition at a critical magnetic field H(c). The simultaneous metaelectric and spin-flop transitions become sharper upon cooling but remain a continuous cross-over even down to 0.5 K. Near the P = 0 line realized at mu(0)H(c) approximately 18 T below 20 K, the dielectric constant (epsilon) increases significantly over wide field and temperature (T) ranges. Furthermore, a characteristic power-law behavior is found in the P(H) and epsilon(H) curves at T = 0.66 K. These findings indicate that a magnetic-field-induced metaelectric critical end point is realized in BiMn(2)O(5) near zero temperature.

15.
J Neurosurg Pediatr ; 29(6): 659-666, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35364592

RESUMO

OBJECTIVE: Bilateral coronal craniosynostosis in Apert syndrome is traditionally managed with open cranial vault remodeling procedures like fronto-orbital advancement (FOA). However, as minimally invasive procedures gain popularity, limited data exist to determine their efficacy in this syndromic population. This study examines whether endoscopic strip craniectomy (ESC) is inferior to FOA in correcting head growth in patients with Apert syndrome. METHODS: The authors conducted a retrospective review of children with Apert syndrome over a 23-year period. Postoperative head circumferences until 24 months of age were compared for patients treated with ESC versus FOA by using normative growth curves. Intraoperative and postoperative morbidity was compared between groups. RESULTS: The median postoperative follow-up for the FOA (n = 14) and ESC (n = 16) groups was 40 and 28.5 months, the median age at operation was 12.8 and 2.7 months, and the median operative time was 285 and 65 minutes, respectively (p < 0.001). The FOA group had significantly higher rates of blood transfusion, ICU admission, and longer hospital length of stay (p < 0.01). There were no statistically significant differences in premature reossification rates, complications, need for further procedures, or complaints of asymmetry. Compared to normative growth curves, all patients in both groups had head circumferences comparable to or above the 85th percentile at last follow-up. CONCLUSIONS: Children with Apert syndrome and bilateral coronal craniosynostosis treated with ESC experience early normalization of head growth and cephalic index that is not inferior to those treated with FOA. Longer-term assessments are needed to determine long-term aesthetic results and the correlation between head growth and neurocognitive development in this population.


Assuntos
Acrocefalossindactilia , Craniossinostoses , Humanos , Criança , Lactente , Acrocefalossindactilia/cirurgia , Acrocefalossindactilia/etiologia , Resultado do Tratamento , Craniossinostoses/cirurgia , Craniotomia/métodos , Crânio/cirurgia , Estudos Retrospectivos
16.
Phys Rev Lett ; 105(6): 066103, 2010 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-20867990

RESUMO

The evolution and annealing of pores in, and the crystallization of, vapor-deposited films of amorphous solid water have been studied by using variable-energy positron annihilation spectroscopy for temperatures in the range 50-150 K. Both positron and positronium annihilation provide insight to the nature of the grown-in pores and their evolution with temperature. Crystallization of the films was observed at just below 140 K, in agreement with earlier studies, with the topmost 80 nm undergoing a transition consistent with crystallization at 90-100 K.

17.
Phys Rev Lett ; 104(18): 186402, 2010 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-20482193

RESUMO

The canonical view of heavy fermion quantum criticality assumes a single quantum critical point separating the paramagnet from the antiferromagnet. However, recent experiments on Yb-based heavy fermion compounds suggest the presence of non-Fermi liquid behavior over a finite zero-temperature region. Using detailed susceptibility and transport measurements we show that the classic quantum critical system, Ge-substituted YbRh(2)Si(2), also displays such behavior. We advance arguments that this is not due to a disorder-smeared quantum critical point, but represents a new class of metallic phase.

18.
Nature ; 424(6948): 524-7, 2003 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-12891349

RESUMO

The point at absolute zero where matter becomes unstable to new forms of order is called a quantum critical point (QCP). The quantum fluctuations between order and disorder that develop at this point induce profound transformations in the finite temperature electronic properties of the material. Magnetic fields are ideal for tuning a material as close as possible to a QCP, where the most intense effects of criticality can be studied. A previous study on the heavy-electron material YbRh2Si2 found that near a field-induced QCP electrons move ever more slowly and scatter off one another with ever increasing probability, as indicated by a divergence to infinity of the electron effective mass and scattering cross-section. But these studies could not shed light on whether these properties were an artefact of the applied field, or a more general feature of field-free QCPs. Here we report that, when germanium-doped YbRh2Si2 is tuned away from a chemically induced QCP by magnetic fields, there is a universal behaviour in the temperature dependence of the specific heat and resistivity: the characteristic kinetic energy of electrons is directly proportional to the strength of the applied field. We infer that all ballistic motion of electrons vanishes at a QCP, forming a new class of conductor in which individual electrons decay into collective current-carrying motions of the electron fluid.

19.
Nature ; 432(7019): 881-5, 2004 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-15602556

RESUMO

A quantum critical point (QCP) develops in a material at absolute zero when a new form of order smoothly emerges in its ground state. QCPs are of great current interest because of their singular ability to influence the finite temperature properties of materials. Recently, heavy-fermion metals have played a key role in the study of antiferromagnetic QCPs. To accommodate the heavy electrons, the Fermi surface of the heavy-fermion paramagnet is larger than that of an antiferromagnet. An important unsolved question is whether the Fermi surface transformation at the QCP develops gradually, as expected if the magnetism is of spin-density-wave (SDW) type, or suddenly, as expected if the heavy electrons are abruptly localized by magnetism. Here we report measurements of the low-temperature Hall coefficient (R(H))--a measure of the Fermi surface volume--in the heavy-fermion metal YbRh2Si2 upon field-tuning it from an antiferromagnetic to a paramagnetic state. R(H) undergoes an increasingly rapid change near the QCP as the temperature is lowered, extrapolating to a sudden jump in the zero temperature limit. We interpret these results in terms of a collapse of the large Fermi surface and of the heavy-fermion state itself precisely at the QCP.

20.
Nature ; 407(6802): 351-5, 2000 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-11014185

RESUMO

There are two main theoretical descriptions of antiferromagnets. The first arises from atomic physics, which predicts that atoms with unpaired electrons develop magnetic moments. In a solid, the coupling between moments on nearby ions then yields antiferromagnetic order at low temperatures. The second description, based on the physics of electron fluids or 'Fermi liquids' states that Coulomb interactions can drive the fluid to adopt a more stable configuration by developing a spin density wave. It is at present unknown which view is appropriate at a 'quantum critical point' where the antiferromagnetic transition temperature vanishes. Here we report neutron scattering and bulk magnetometry measurements of the metal CeCu(6-x)Au(x), which allow us to discriminate between the two models. We find evidence for an atomically local contribution to the magnetic correlations which develops at the critical gold concentration (x(c) = 0.1), corresponding to a magnetic ordering temperature of zero. This contribution implies that a Fermi-liquid-destroying spin-localizing transition, unanticipated from the spin density wave description, coincides with the antiferromagnetic quantum critical point.

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