Objective:To validate the morphological changes of the parieto-occipital sulcus on the transcalvarial axial plane between 20 and 32 weeks of gestation, simplify grade for assessing fetal parieto-occipital sulcus development, and confirm its clinical feasibility.Methods:This was a cross-sectional study analysis that included 550 cases of normal singleton fetuses between 20 and 32 weeks of gestation, who underwent routine ultrasound examinations at Shenzhen Maternity and Child Healthcare Hospital from September 2019 to June 2022. The morphological changes of the bilateral parieto-occipital sulci on the transcalvarial axial plane were observed. The development of the parieto-occipital sulcus was classified into 6 grades based on the developmental features of angulation, progressive closure, and curvilinear growth: straight or shallow arcuate (Grade 0), shallow and wide V-shaped (Grade 1), deep and narrow V-shaped (Grade 2), Y-shaped (Grade 3), I-shaped (Grade 4), and curvilinear (Grade 5). The gestational age at examination and pregnancy outcomes were recorded. The distribution of gestational weeks for fetuses with different grades of parieto-occipital sulci on the left and right sides was analyzed. The symmetry between bilateral parieto-occipital sulcus gradings within individuals, as well as the inter-observer and intra-observer reliability were assessed using the Weighted Kappa coefficient. The gender differences in asymmetry of parieto-occipital sulci grades between the left and right sides was analyzed. Moreover, a model for predicting the grade of the parieto-occipital sulcus based on gestational week was established.Results:Grade for the left parieto-occipital sulcus was obtained for 549 fetuses, while grade for the right was obtained for 550 fetuses. From 20 to 32 weeks of gestation, the morphology of the fetal parieto-occipital sulcus was divided into Grade 0-5, progressing from low to high with gestational development. Grade 0 showed that the sulcus was not visible or only had a slight arcuate indentation, occurring at 20-22 weeks; Grade 1 presented as a shallow and wide "V" shape with an obtuse angle at the top, appearing from 20 to 27 weeks; Grade 2 was a deep and narrow "V" shape with an acute angle at the top, appearing from 24 to 29 weeks; Grade 3 appeared as a "Y" shape with the top part partially closed and the bottom still open, occurring between 26 to 30 weeks; Grade 4 was a fully closed "I" shape, appearing at 29-32 weeks; Grade 5 presented as a curved shape, indicating the parieto-occipital sulcus was approaching maturity, appearing from 31 to 32 weeks. There was no statistically significant difference in the distribution of gestational weeks for bilateral parieto-occipital sulcus developmental grade ( P>0.05). Bilateral parieto-occipital sulcus grade could be assessed in 549 fetuses, of which 43 cases (7.83%) exhibited grade asymmetry with a one-grade difference between sides; such asymmetry showed no significant difference between male and female genders ( P=0.647). The weighted kappa coefficient analysis results indicated a strong consistency in the development of the parieto-occipital sulci on both sides within individuals, generally demonstrating symmetrical development ( P<0.001). The intra-observer and inter-observer weighted kappa coefficients were 0.92 and 0.75, respectively, with good consistency. Conclusions:Prenatal ultrasound via the transcalvarial axial plane enables a preliminary and rapid assessment of the development of bilateral parieto-occipital sulci, facilitating early evaluation of fetal cortical maturation.

Objective:To study the stability and morphological changes of the convexity sulci in normal fetuses between 20 and 32 weeks, and to explore the simplified grade for evaluating the convexity sulci development and analyzing its clinical significance.Methods:This study was a cross-sectional analysis. A total of 551 cases of normal singleton pregnancies between 20 and 32 weeks of gestation were retrospectively collected, who underwent routine ultrasound examinations at Shenzhen Maternity and Child Healthcare Hospital from September 2019 to June 2022. The display of the far-field convexity sulci on the transcalvarial axial plane was observed as 0 for not displayed and 1 for displayed.Further, based on the morphology and number of convexity sulci, they were classified into five grades: no sulcus displayed (grade 0), one sulcus (grade 1), two sulci (grade 2), three sulci (grade 3), and four or more sulci (grade 4). The gestational age at examination and pregnancy outcomes were recorded. The distribution characteristics of gestational weeks for each grade of the convexity sulci were analyzed, and the gestational week distribution of the left and right convexity sulci was compared to analyze bilateral symmetry. The Weighted Kappa coefficient was used to analyze inter-observer and intra-observer consistency, and curve regression analysis was employed to establish a model for predicting grade based on gestational weeks.Results:Before 25 weeks of gestation, the convexity of the fetal cranial vertex was completely smooth.The central sulcus consistently appeared after 26 weeks, while the superior frontal sulcus, intraparietal sulcus, postcentral sulcus, and precentral sulcus consistently appeared between 28 and 31 weeks. Among these, the superior frontal sulcus had a lower display rate before 29 weeks. By 32 weeks, all convexity sulci of the cranial vertex should be visible. Three hundred and eleven fetuses were graded for the left, and 240 fetuses were graded for the right. The developmental grade of the convexity sulci increased from Grade 0 to Grade 4 as the gestational age progressed. Grade 0 appeared between 20-26 weeks, grade 1 between 25-28 weeks, grade 2 between 26-28 weeks, grade 3 between 27-30 weeks, and grade 4 between 27-32 weeks. The distribution of grade did not differ significantly between the left and right sides of grade 0, 1, 3 and 4 (all P>0.05), while there was a significant difference in the distribution of gestational age between the convexity sulci of grade 2 ( P<0.05). The Weighted Kappa coefficients for intra-observer and inter-observer consistency were 0.94 and 0.86, respectively, indicating strong consistency. Conclusions:The simplified grade for assessing the development of convexity sulci in normal fetuses on the transcalvarial axial plane via prenatal ultrasound can provide a preliminary evaluation of the maturation of convexity sulci in fetuses between 20 and 32 weeks of gestation.

Objective To explore the genetic characteristics of fetuses with congenital heart diseases(CHD)diagnosed by prenatal ultrasound.Methods Data of 613 singletons with prenatal ultrasonic diagnosed CHD were retrospectively analyzed.The cardiac structural abnormalities were classified into 8 types.Whole-exome sequencing(WES)was performed for 40 fetuses since chromosomal karyotyping analysis and/or chromosomal microarray analysis(CMA)showed benign copy number variations(CNV)or variants of uncertain significance(VUS).Results Among 613 fetuses,479 fetuses underwent both chromosomal karyotyping analysis and CMA,genomic abnormalities were detected in 60 fetuses(60/479,12.53％).Among 134 fetuses underwent only CMA,genomic abnormalities were found in 4 fetuses(4/134,2.99％).According to results of chromosomal karyotyping analysis and/or CMA,abnormalities were noticed in 40 fetuses(40/568,7.04％)among 568 fetuses with isolated CHD,while in 15 fetuses(15/45,33.33％)among 45 fetuses with non-isolated CHD,respectively.Abnormality detection rate of chromosomal karyotyping analysis and/or CMA in fetuses with complex CHD(10/41,24.39％)was higher than that in fetuses with non-complex CHD(54/572,9.44％).Among complex CHD fetuses,abnormality detection rate was the highest in fetuses with conotruncal defect(CTD)combined with malformation of venous system(4/13,30.77％),while among fetuses with non-complex CHD,situs inversus viscerum had the highest detection rate(1/4,25.00％).Among 40 fetuses chromosomal karyotyping analysis and/or CMA showed benign CNV or VUS,WES indicated pathogenic CNV/likely pathogenic CNV(P/LP)in 3 fetuses,VUS in 3 fetuses and benign CNV in 34 fetuses.Conclusion Fetuses with CHD,especially extracardiac malformations had possibilities of genomic abnormalities.Fetuses with CTD combined with malformation of venous system had higher possibilities of genomic abnormalities.Compared with CMA alone,chromosomal karyotyping analysis combined with CMA was helpful for detecting genomic abnormalities.

Objective:To assess the ultrasonographic features and potential diseases of fetal abnormal sylvian fissure(SF), and to explore the value of whole-genome sequencing (WGS) in prenatal detection.Methods:A total of 28 fetuses with a sonographic diagnosis of abnormal SF in Shenzhen Maternal and Child Health Hospital Affiliated to Southern Medical University between October 2018 and October 2020 were prospectively included. The fetal brain was evaluated by neuroultrasound and intrauterine MRI in detail. Amniotic fluid/cord blood obtained by amniocentesis or tissue samples from umbilical cord after birth were collected for WGS. Pregnancy outcomes and postnatal MRI were recorded, and neurodevelopment of live-born infants was followed up for more than 24 months after delivery.Results:During the study period, 28 fetuses with abnormal SF were identified, with a gestational age of 21.3-30.0 (24.8±2.0) weeks. Abnormal SF presented in MCD ( n=15, 53.6%), chromosomal anomalies ( n=3, 10.7%) or single-gene genetic syndromes ( n=3, 10.7%) with the affected fetuses showing developmental delay, hydrocephalus or leukomalacia ( n=4, 14.2%), corpus callosal agenesis with large interhemispheric cysts ( n=1, 3.6%), benign subarachnoid space enlargement with arachnoid cysts ( n=1, 3.6%), and multiple malformations ( n=1, 3.6%). Among the 15 cases with MCD, the most common pathology was lissencephaly/pachygyria, followed by schizencephaly, severe microcephaly, hemimegalencephaly with paraventricular heterotopia, and polymicrogyria. Abnormal SF presented bilaterally in 23 fetuses and unilaterally in 5. All cases were categorized into six types depending on SF morphology in the transthalamic section: no plateau-like or a small insula, linear type, irregular corrugated SF, Z-shaped, and cyst occupying type. In addition to abnormal SF, associated anomalies or mild variations were identified in all fetuses. There were 17 cases underwent intrauterine MRI, and 13 cases underwent postnatal MRI examination.And 25 pregnancies were terminated; 3 were born alive, and 2 had typical syndromic changes with poor neurodevelopmental prognosis. A related pathogenic genetic variant was detected in 57.1% (16/28) fetus, and the incidence of single nucleotide variants(SNVs) was 42.9% (12/28), among which de novo SNVs accounted for 91.7% (11/12). Conclusions:Fetal abnormal SF could be classified based on the ultrasonographic features of transthalamic section. Fetal abnormal SF may indicate MCD, some chromosomal abnormalities or single-gene genetic syndromes that may lead to poor neurodevelopmental outcomes, and may be affected by extra-cortical factors. It is suggested to carry out targeted prenatal genetic diagnosis for fetuses with abnormal SF.

ObjectiveTo determine the virulence of desert-type Leishmania donovani strains through animal infection experiments and to explore preservation methods for maintaining their pathogenicity.Methods The isolated strain was cultured in vitro for 7, 30, 36, 44, 60, 90, and 150 days, respectively， and inoculated into Lagurus lagurus (L.lagurus) with the dose of 2.6×10⁵ per animal by intraperitoneal injection. The spleen coefficient, infection rate, and antibody positive rate of the inoculated animals were detected at day 60 after infection. The desert-type Leishmania donovani strain was further inoculated with Cricetulus migratorius (C.migratorius) and L. lagurus, respectively, for passaging and preservation. The survival time of two kinds of animals andpathogenicity change of the stain in their bodies were compared.ResultsAfter inoculation of desert-type Leishmania donovani strains cultured in vitro for 7-150 days, the spleen coefficient of inoculated L.lagurus gradually increased from 1% on day 7 to 2.2% on day 30, which was more than 10 times of the normal spleen coefficient. Additionally, on day 60, the spleen coefficient remained 3 times higher than the normal value. The infection rate and antibody positive rate decreased from 80% on day 7 to 0% on day 60. At 90 days, there were no significant differences between the infected groups and the control group, and all the observed indexes were within the normal range. The survival time of L.lagurus infected with the in vivo passage strain ranged from 1 to 13 months, and half of the infected individuals died within 4 months. In contrast, C.migratorius had a survival time ranging from 5 to 31 months, and half of the infected individuals died within an average of 13.7 months. There was a significant difference in the average time of death between the two groups (t=0.000 1, P<0.001), but no significant difference in spleen coefficient (t=0.990, P>0.05). This strain exhibited equal virulence in both animals and remained virulent for up to 4 years after continuous passage.ConclusionWith the prolonged culture time, the virulence of the strain decreases gradually. At 90 d, it has no pathogenicity to L. lagurus. Long-term in vitro culture fails to preserve it's pathogenicity to L.lagurus. Only in vivo inoculation can maintain the virulence of this strain.

Objective:To observe the morphological changes of the sylvian fissure on the transthalamic section of fetal brain at 20-32 weeks, and grade the fetal sylvian fissure development by means of a simple scoring system and explore its clinical feasibility.Methods:From September 2018 to June 2020, 487 normal single fetuses of 20-32 weeks were examined in Shenzhen Maternal and Child Health Hospital Affiliated to Southern Medical University. The sylvian fissure maturation was analyzed on the transthalamic section of fetal brain at 20-32 weeks and was graded from 0 to 5: un-visualized (grade 0), shallow arc (grade 1), obtuse-angled platform (grade 2), right-angled platform (grade 3), acute-angled platform (grade 4), and closed operculum (grade 5). The pregnancy outcomes and gestational age were recorded.Statistical analysis was performed by SPSS 20.0 software using box plot, Mann-Whitney U test, Weighted Kappa coefficient. Results:Left sylvian fissuer grades were obtained in 280 fetuses and right sylvian fissure grades were obtained in 247 fetuses. The fetal sylvian fissure maturation at 20-32 weeks was graded from 0 to 5, which increased with advancing gestation. Grade 0 only appeared in 3 fetuses at 20 weeks, and 99.4% fetuses at 20 weeks had grade ≥1. Grade 1 appeared in 20-22 weeks, grade 2 in 20-25 weeks, grade 3 in 22-26 weeks, grade 4 in 25-32 weeks, and grade 5 in 27-32 weeks. Box-plot and Mann-Whitney U test showed that gestational week distribution of sylvian fissure at all grades was symmetric on both sides ( P>0.05). The Weighted Kappa coefficients were 0.857(95% CI=0.750-0.957) and 0.939 (95% CI=0.859-1.000), respectively, with strong consistency regarding inter- and intra-observer agreements. Conclusions:Fetal sylvian fissure maturation at 20-32 weeks can be evaluated by means of a simple scoring system with symmetrical grading of both sides.

Objective:To assess the significance of counting the number of caudal vertebral ossification centers (OCN) below fetal terminal conus medullaris in the screening for closed spina bifida and tethered cord syndrome (TCS).Methods:The OCN was counted in 961 normal fetuses(normal group) between 17 and 41 gestational weeks and in 140 fetuses with closed spina bifida or tethered cord syndrome(abnormal group) from Jan.2013 to Dec.2020 in Affiliated Shenzhen Maternity & Child Healthcare Hospital, Southern Medical University, Women and Children′s Hospital, School of Medicine, Xiamen University and Maternity and Child Health Care of Guangxi Zhuang Autonomous Region. The OCN was counted in the dorsal mid-sagittal section of fetal caudal spine.The reliability and agreement test were evaluated by intraclass correlation coefficients in another 50 normal fetuses. The OCN was compared between two groups. ROC curve and the cut-off value were constructed and calculated.Results:In normal group, the N increased with the growing of gestational age.In the subgroup of 17-20 weeks, the OCN ranged from 5 to 7 in most fetuses. In the others subgroups, the OCN was equal to or greater than 6 in 99.9% cases and more than 6 in 97.1% cases. In abnormal group, OCN was less than 7 in 93.0% fetuses and less than 6 in 82.8% cases. There were statistical differences between the two groups except for the subgroup of 17-20 gestational weeks( P<0.05). With the cut-off value of 6.5, the specificity and sensitivity were 93.0% and 94.3% respectively for predicting the presence of closed spinal dysraphism or TCS. Conclusions:OCN is a simple way to evaluate the position of conus medullaris and to screen for the skin-covered spine dysraphism or TSC. OCN is more than 6 in most normal fetuses. Further evaluation of spine is required in fetuses with N less than or equal to 6.

Objective:To share the implementation experience of hierarchical first aid training scheme for elementary and middle school students in Baoan District of Shenzhen City and evaluate its effect of training. Methods:During August 2018 and August 2019, elementary and middle schools students who participated in the first aid training held by emergency rescue training center of Baoan District were enrolled. Baseline information including the number of students, the number of attending tutors, the number of cardiopulmonary resuscitation (CPR) training models, automated external defibrillator (AED) models were recorded. According to hierarchical levels of three age, students received different courses with content from simple to hard: the course of elementary school students was consisting of dialing 120, smart animation on how to identify accidental damage, demonstration of AED and Hemlick techniques, CPR practise (40 minutes). The course of junior high school students was consisted of how to dial 120, how to identify accidental damage and simple disposal, application of CPR and AED, practice CPR and AED and Hemlick techniques (90 minutes). The course of high school students was consisted of how to dial 120, identify accidental damage and right disposal, identification of out-of-hospital cardiac arrest, the key-point of CPR and AED, practice CPR and AED, Hemlick techniques and hemostatic bandage (120 minutes). At the end of course, elementary school students were voluntary for skill assessment; junior high school students only were compulsory for skill assessment in small classes but not required in large classes, just for demonstration; additionally, the whole high school students were compulsory for skill assessment. The characteristics of first aid training students at different levels were collected in order to compare the differences on the usage of CPR training model and AED training model, the distribution of emergency resource, the ratio for passing examination.Results:A total of 12 896 students and 2 086 training instructors took parted in 200 lists of first aid training courses, 8 557 CPR models and 8 493 AED models were used. On average, there are 65.27±5.61 students in each session, and 10.52±10.43 training instructors. There are 43.09±19.06 CPR training models and 42.77±18.61 AED training models. The mean ratio of student to tutor was 6.07±1.47, student to CPR model was 1.54±1.02, and student to AED model was 1.54±1.03. In the end of course, 10 494 students participated in the examination with the participation rate of 81.37%; 10 114 students passed the examination with the passing rate of 96.38%. Hierarchical analysis showed: compare to elementary school students, the average number of junior high school students in every training session significantly increased (cases: 69.94±8.77 vs. 58.69±6.12, P < 0.05), but the average number of high school students in every training session significantly decreased (cases: 57.35±5.79 vs. 58.69±6.12, P < 0.05). The proportion of instructors in junior high school students' training significantly reduced (5.94±1.39 vs. 6.48±2.02, P < 0.05). The examination ratio of junior high school students and high school students was increased significantly [81.07% (6 667/8 224), 100% (2 313/2 313) vs. 64.18% (1 514/2 359), both P < 0.05], but the ratio of passing the examination was significantly reduced [95.47% (6 365/6 667), 96.88% (2 241/2 313) vs. 99.60%(1 508/1 514), both P < 0.01]. This might be related to the low difficulty of elementary school students' assessment and the low proportion of compulsory examination. Conclusions:Hierarchical scheme is feasible for first aid training in elementary and middle school students, the content of course should be desighed from easy to hard. Synchronously, sufficient training instructors and training models should be equipped to ensure the quality.

Objective:To study the clinical application effect of modified nasopharyngeal swab sampling for 2019 novel coronavirus nucleic acid detection.Methods:This study covered the period from January 14 to March 1, 2020.The supine position method and the protective face screen were used to collect nasopharyngeal swabs from February 24 onwards, before which, the nasopharyngeal swabs were collected by sitting position method. All the patients who were diagnosed with suspected/confirmed 2019 novel coronavirus infection were admitted from February 19 with the nasopharyngeal swabs collected outside the hospital before admission. (1) Thirty-four swabbing operators meeting the inclusion criteria of the study were recruited in this retrospective cohort study. They were grouped according to the collection method of nasopharyngeal swabs. Sixteen operators of Wuhan Taikang Tongji Hospital who applied the supine position method and the protective face screen were included in supine position method+ protective face screen group (15 males and 1 female, aged 34-49 years); 18 operators (12 from the First Affiliated Hospital of Army Medical University (the Third Military Medical University), 1 from Wuhan Jiangxia Mobile Cabin Hospital, 5 from the East District of People′s Hospital of Wuhan University) who applied the traditional sitting position method were included in sitting position method group (2 males and 16 females, aged 25-49 years). In supine position method+ protective face screen group, when collecting sample, the patient lay flat and wore a special protective face screen for nasopharyngeal swab sampling, with neck slightly extending and face turning to the opposite side of the operator about 10°. The self-designed questionnaire was used to investigate the cooperation, the incidence of nausea, coughing, sneezing, and struggling of patients evaluated by the operators, the operation time for a single swab sample, the fear of operation and the perceived exposure risk of operators in the two groups. (2) Sixty-five patients (22 males and 43 females, aged 25-91 years) admitted to Wuhan Taikang Tongji Hospital who successively received the sitting position method and supine position method+ protective face screen for nasopharyngeal swabs sampling and with complete nucleic acid detection results were included. The positive rates of nucleic acid detection by the two sampling methods of nasopharyngeal swabs of the patients were statistically analyzed. (3) Forty-one patients who could express their feelings accurately were selected out of those 65 patients (12 males and 29 females, aged 27-83 years). The comfort of patients in the process of sampling by the two methods was investigated. (4) Thirty-four patients (10 males and 24 females, aged 25-83 years) with two or more consecutive negative results of nucleic acid detection of nasopharyngeal swabs by sitting position method were selected from the above 65 patients. The positive rate of nucleic acid detection of nasopharyngeal swab of patients by supine position method+ protective face screen, i. e. negative to positive rate was statistically analyzed. Data were statistically analyzed with t test, Wilcoxon signed rank test, and chi-square test. Results:(1) Compared with those of sitting position method group, the cooperation score of patients evaluated by the operators in supine position method+ protective face screen group was significantly higher ( Z=-4.928, P<0.01), the incidence of nausea, choking cough, sneezing, and struggling of patients evaluated by the operators, and the fear of operation score and the perceived exposure risk score of operators in supine position method+ protective face screen group were significantly lower ( Z=-5.071, -5.046, -4.095, -4.397, -4.174, -5.049, P<0.01), and the operation time for a single swab sample in supine position method+ protective face screen group was significantly longer ( t=223.17, P<0.01). (2) The positive rate of nucleic acid detection of nasopharyngeal swabs by supine position method+ protective face screen was 60.00% (39/65), which was obviously higher than 41.54% (27/65) by sitting position method ( χ2=4.432, P<0.05). (3) The comfort score of the 41 patients during nasopharyngeal swabs sampling by supine position method+ protective face screen was significantly higher than that by sitting position method ( Z=-5.319, P<0.01). (4) Of the 34 patients with two or more consecutive negative results of nucleic acid detection of nasopharyngeal swabs by sitting position method, the rate of negative to positive of nucleic acid detection was 26.47% (9/34) after sampling by supine position method+ protective face screen. Conclusions:Compared with the traditional sitting position method, detection of 2019 novel coronavirus nucleic acids of nasopharyngeal swabs collected by supine method combined with protective face screen is worth promoting, because of its better comfort of patients, low exposure risk for operators, in addition to reducing in the false negative result to some extent, which may help reduce false recurrence of discharged patients.

Objective To investigate the clinical treatment and outcomes of severe community-acquired pneumonia (CAP) complicated with mediastinal emphysema after renal transplantation. Methods Clinical data of9 patients with severe CAP complicated with mediastinal emphysema after renal transplantation were retrospectively analyzed. The acute physiology and chronic health evaluationⅡ(APACHEⅡ) and oxygenation index were recorded when the patients were admitted to the intensive care unit (ICU). The complications of mediastinal emphysema and corresponding treatment were observed. The treatment course during the ICU, mortality rate in ICU, ICU stay time and hospital stay time were recorded. All patients underwent pathogenic examinations. Results The APACHEⅡ score of9 patients with severe CAP complicated with mediastinal emphysema after renal transplantation was 14 (8-21) scores and the oxygenation index was 150 (133-189) mmHg. Among 9 patients, 3 cases were infected by bacteria alone, 3 cases were infected by bacterial infection combined with viral infection, 1 case was infected by mycobacterium tuberculosis complicated with other bacterial infection and 1 case was viral infection. No pathogenic evidence was detected in the remaining 1 patient. Mediastinal emphysema complicated with subcutaneous emphysema occurred in 7 cases and pneumothorax occurred in 6 cases. Treatment methods included anti-infection, modified immunosuppressive program, mediastinal drainage, thoracic closed drainage, subcutaneous incision and extracorporeal membrane oxygenation (ECMO) treatment. Six patients received invasive mechanical ventilation (IMV), 2 received non-invasive positive pressure ventilation (NIV) and 1 received high-flow nasal oxygen cannula (HFNC). Among 9 patients, the mortality rate in ICU was 6/9, the remaining 3 patients were recovered and discharged, the ICU stay time was 26 (17-40) d, and the total hospital stay time was 27-61 d. Conclusions Mediastinal emphysema is a serious complication of patients presenting with severe CAP after renal transplantation with a high mortality rate. For these patients, imaging evaluation, timely drainage and full sedation should be strengthened, and ECMO treatment should be delivered when necessary.